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Reprinted from the May 1967 Issue of WATER AND WASTES ENGINEERING Copyright 1967 by The Reuben H. Donnelley Corporation PLAINTIFF'S EXHIBIT CT-1249 WATER SYSTEMS pipes and piping o water and wastes / engineering / MANUAL OF PRACTICE NUMBER TWO PART 1/PIPING SYSTEM DESIGN PART 2/MATERIALS PART 3/INSTALLATION PART 4/MAINTENANCE CTD000086 GEORGE E. SYMONS, PH.D. PUBLISHED BY DUN DONNELLEY PUBLISHING CORPORATION, 666 FIFTH AVE., NEW YORK, NEW YORK 10019 MAY 1967 | M 1 water and wastes / engineering / manual f practice number two CONTENTS PART 1/PIPING SYSTEM DESIGN Section 1--Transmission lines.................................... M3 Location .....................................................................M3 Type of line................................................................ M3 Capacity .....................................................................M3 Materials.....................................................................M4 Section 2--Distribution system..................................M4 Components ..............................................................M4 System planning....................................................... M5 Sizing mains..............................................................M5 Materials..................................................................... M7 Section 3--Services....................................................... M7 Materials..................................................................... M7 Sizing services............................................................M7 Location and ownership......... ..............................M8 Section 4--Inplant systems......................................... M8 Design..........................................................................M8 Material selection....................................................... M8 Layout and arrangement............................................M8 Color-coding ............................................................. PART 2/MATERIALS Section 1--Asbestos-cement................... Design...................................................... Manufacture .......................................... Testing ................................................... Surface characteristics.......................... Pipe sizes............................................... Joints ...................................................... Shipping ................................................. Section 2--Cast iron pipe........................ Design...................................................... Manufacture .......................................... Testing .................................................... Coating and lining................................. Pipe sizes............................................... Joints ...................................................... Shipping ................................................. Section 3--Concrete pipe........................ Design...................................................... Manufacture .......................................... Testing and rejection............................. Coating and lining................................. Pipe sizes............................................... Joints ...................................................... Shipping ................................................. Section 4--Plastic and plastic-lined pipe Design...................................................... M9 M9 MID Mil Ml 2 Ml 2 Ml 2 Ml 2 Ml 3 Ml 3 Ml 5 Ml 6 Ml 7 Ml 7 Ml 7 Ml 8 M18 Ml 8 M20 M20 M21 M21 M21 M21 M22 M22 Manufacture ............................................ Pipe sizes ................................................. Testing ..................................................... Joints ....................................................... Plastic-lined pipe..................................... Section 5--Steel pipe................................. Design........................................................ Manufacture ............................................ Testing ..................................................... Coating and lining................................... Section 6--Wood-stave pipe....................... Design........................................................ Manufacture ............................................ Section 7--Wrought iron pipe................... Design....................................................... Manufacture ............................................ Section 8--Service lines............................ Section 9--Inplant systems....................... PART 3/INSTALLATION Section 1--Transmission and distribution Pipe handling............................................ Trenching ................................................. Joints ....................................................... Laying pipe............................................ . Testing ................................................... Backfilling............................................... Disinfection............................................ Section 2--Service lines.......................... Equipment.............................................. Trenching ............................................... Tapping................................................... Laying and backfilling.......................... Section 3--Inplant systems..................... PART 4/MAINTENANCE Section 1--Pipe line leakage................... Leak surveys.......................................... Leak repair............................................ Section 2--Loss of carrying capacity . .. Coefficient tests..................................... Remedies ............................................... Section 3--Cleaning and lining.............. Cleaning ................................................. Lining ...................................................... Section 4--Cathodic protection.............. Section 5--Services................................... Thawing ................................................. Cleaning ................................................. M23 M24 M24 M2S M26 M26 M2G M28 M29 M30 M31 M31 M31 M31 M32 M32 M34 M34 M35 M35 M35 M35 M38 M40 M40 M41 M42 M42 M42 M42 M43 M43 M44 M44 M44 M4S M45 M45 M45 M4S M4G M47 M47 M47 M47 FOREWORD this manual of practice, the second in a projected series to be published by water and wastes engineering, has been prepared for a specific purpose; namely, to assemble, digest, collate, and organize basic information on pipes and piping systems used in water supply systems. No manual of this size or type can include all of the myriad of details that apply to different types of pipe materials, their design, installation, and maintenance. This manual is not intended to be a detailed compendium. It M 2 | WATER AND WASTES ENGINEERING was prepared to provide concise and basic information on the general subject. A glossary of terminology relating to pipes and piping will appear in Manual of Practice No. 3/Wastewater Systems Pipes and Piping. It is hoped that this manual will be of interest and use to managers, superintendents, designers, engineers, and oper ators of municipal and investor-owned utilities and industrial water supply systems, and to teachers and students as well. CTD000087 water and wastes / engineering / MANUAL OF PRACTICE NUMBER TWp WATER SYSTEMS pipes and piping PART 1/ PIPING SYSTEM DESIGN the origin of the closed conduit, or pipe, is unknown, but in importance to mankind, its discovery ranks only be hind those of fire, the wheel, and the lever. It is known that copper pipes were used in Egypt in 3800 B.C. The Chinese probably used hollow bamboo as pipes about the same time or even earlier. Tile pip? was used in palaces in the Middle East in 2500 B.C., and by King Solomon in 1500 B.C. Lead pipe was used for service connections to aqueducts by the Romans between 300 B.C. and 450 A.D. Modem water pipe had its origin in the development of cast iron cannons in Europe in the mid-14th century. Early water pipes in England and America were bored logs. The first cast iron water distribution system in England was laid in 1774; and the first in America'was in Philadelphia in 1802. All other water piping system materials now being used have been developed since 1900. The importance of water pipe lines to the economy and to the water industry is evident from these facts: As a transportation system, water pipe lines carry a greater tonnage of product per day than any other single transportation system. Approximately two-thirds of the total value of water supply systems is in the transmission and distribu tion systems. Approximately 80 percent of the value of a distribu tion system is in piping and valves. In the five-year period 1961-65, approximately 48 per cent of the total construction costs for water supply systems was for transmission and distribution (19 and 29 percent, respectively). There are four types of p.iping systems in water utilities: transmission lines, distribution mains, services, and in-plant systems. Pipe lines are fixed-installation facilities; they contain no moving parts (except in valves). Therefore, pipelines do not operate; neither are they operated, per se. Any discussion of transmission and distribution system operation actually re fers to the water that flows in the pipes. Included in the subject of operation of these systems are these topics: boost er stations, centralized control, extension of mains, fire flow tests, leakage surveys, metering (main line), nonrevenue water, pump control, records, sanitary checks, storage, and valves and hydrants. The latter topic on valves and hydrants is scheduled for coverage in Manual of Practice No. 4, and the other topics will be covered in another scheduled manu al on distribution system operation. Operation of services is, in reality, a matter principally of metering and customer service, to be covered in a manual on management. Operation of inplant piping systems will be covered in a manual on treatment plant operation. M GEORGE E. SYMONS, PH.D. WATER AND WASTES ENGINEERING. He IS a Diplo- n* icr-V.TM*j 5lc.an Academy of Environmental Engineers: a Fellow ,V&,Men,b FuU" Awardee of (WWA: an TM? KK?pMTn!t?r ( WPCF; and a Member of ACS, AIChE, Alf>IS, hi. rticl on water supply and wastewater *^llo.r, of 28 design criteria manuals for the Engineering F-.S- Navy, and author and editor of two rnanu.U EFC ofttfu!"S*NlfvyWater `UPPy *ndW*'"W*"r dUpMal Section 1--Transmission Lines Transmission lines are pipes (or open conduits) that carry water from a source of supply to a treatment works or from a treatment works and/or main pumping station to a distribution system in a community. The design of transmission lines must take into account these factors: location, type, carrying capacity (size), oper ating head and velocity, friction loss, material of construc tion, and installation conditions. Location Information required for the design of transmission lines includes a topographic map, soil map, and climatic data. If the line is to be a tunnel, a geologic survey is also necessary. The route selected should provide economical construc tion and also have as many as possible of the following characteristics: gravity flow; shortest possible distance; few, if any, peaks and depressions; accessibility for construction and repairs, and freedom from landslides and flood waters. When possible, it is often desirable to lay transmission lines along highways to avoid right-of-way costs. However, such locations should be used only if there is assurance that no future relocation will be required when the highway is widened, regraded, or moved. Type of line Choice of line type depends on several factors; for ex ample: Aqueducts or canals may be used under special circum stances but are not usually employed in this country. Tunnels, either gravity or pressure, may be used if there is no alternative or where economy of construction dictates their use. Pipe lines are generally preferable to other types, but they should be designed for gravity flow, if possible, to avoid pumping costs and to reduce line pressure. Capacity Transmission lines should be designed to meet future heeds, domestic demands, fire flow demands, and flow ve locity limitations. Future requirements. Transmission lines should be sized to provide the capacity that will be desired at least 25 years hence. This capacity must be sufficient to provide domestic, industrial, and fire flow demands. In some cases, it may be desirable to lay two parallel lines, some distance apart, each line with a capacity equal to 75 percent of the capacity required 25 years later. The actual pipe size (diameter) should be such as to provide the desired capacity at the design working pressure. Domestic demand. The per capita consumption to be pro vided varies with the size of the community. Statistical data for 1960 by Seidel and Cleasby1 show that water produc tion is related to population size (Table 1). These data show that water consumption (production) varies with community size and that the ratio of mean con- CTD000088 MAY 1967 | M 3 Steel transmission main in mountains of Utah. sumption to maximum demand may range from 1 : 4 in small communities to 1: 1.6 or 1:1.9 in large cities. A compromise design criteria should provide transmis sion lines with 150 percent of mean consumption, or pro vide storage on the distribution system for peak loads. With out storage, the capacity must be able to meet peak hour de mands. TABLE I--WATER UTILITY PRODUCTION BY POPULATION GROUPS Production (sped) Group Population Min. Max. Mean 1 1000 (85) 2 1,000-5,000 29 495 121 3 5,000-10,000 29 446 123 4 10,000-25,000 30 353 124 5 25.000-50,000 52 543 137 6 50,000-100.000 45 371 129 7 100,000-250,000 66 359 137 8 250,000-500,000 71 214 131 9 500,000 73 274 147 4-9(1960) 128 4-9(1955) 137 4-9(1950) 138 Fire flow. Water system capacity must meet the criteria of the American Insurance Association (AIA), formerly NBFU. In general, it is necessary to provide sufficient flow capacity to meet both domestic demand plus a fire-flow ca pacity according to this equation.2 gpm = 1020v/p X (1 - 0.01 VP) where P = 1000 persons Eq. 1 The AIA generally requires that this fire-flow capacity be available for 10 hr in cities of 6000 or more and for 4 to 9 hr in communities of 1000 to 5000 population. Where it is uneconomical to provide this fire-flow capacity plus domes tic demand, then storage on the distribution system must be provided to meet this fire-flow demand. Burdick'' developed a table of rates of flow required and storage necessary in communities of various sizes (see Table 2). These data are applicable to both transmission lines and distribution systems. Flow velocity. Velocity of flow is a factor in capacity as are operating head and head loss. Velocities should normally be 5 fps or less because of high friction losses. If higher velocities are necessary, however, they should not exceed 15 fps in pipe or 12 fps in unlined tunnels. Materials The various materials available for water supply system pipe lines are set forth in Table 3, adapted from NAVDOCKS DM-5, (Facilities Engineering Command, U. S. Navy).' Selection factors include corrosion resistance, strength against internal and externa! pressures, hydraulic character istics installation and field conditions, and economic con siderations. These factors will be covered in Part 2 of this manual. Structural requirements. All pipe selected should meet the requirements as set forth in the standards and hand books of the American Water Works Association. (See Table 4.) Protective coatings that provide corrosion resistance must be used wherever soil or water conditions warrant. For in formation on protective coatings see Part 2 of this manual. Installation Criteria for and methods of installing transmission pipe lines are given in Part 3 of this manual. Interconnections should be provided, wherever possible, with nearby potable supplies. Section 2--Distribution System Distribution systems are pipelines (mains) that carry water from transmission lines and distribute it throughout a community. Distribution systems include a network of mains plus distributing reservoirs, elevated storage tanks, booster stations, valves, hydrants, and service lines. (Note: this manual of practice deals only with mains and service lines; other elements will be covered in future manuals.) Components Arterial mains. Sometimes called trunk mains or feeders, arterial mains are pipe lines of fairly large size connected to transmission lines, and they feed the distribution network. All major demand areas should be served by an arterialloop system. Where possible, arterial mains should be laid in duplicate, but not in the same street. It is preferable to lay two moderately-sized arterial mains a few blocks apart than to lay a single large main. If laid in duplicate, arterial mains should be cross-connected at intervals of one mile or so, with the valving arrangements necessary to provide iso lation of areas. Air relief valves and blowoffs need to be pro vided at high and low points respectively. Interconnections should be provided, either on transmission lines or arterial mains, to nearby potable supplies. Distribution mains. All major demand areas should be supplied by distributors tied to the arterial loop to form a complete gridiron system, without dead ends. Areas of extra hazard should be tied into two arterial mains where possi ble. Tree arrangement systems are not recommended. Minor distributors. These components make up the sec ondary system or grid; they supply fire hydrants and domes tic and commercial consumers. TABLE i--RATES OF FLOW REQUIRED IN CITIES OF VARIOUS SIZES Population Flow at 140 sped (mod) 150% of probable max. dally flow (mod) 300% of probable hourly peak (mod) 1,000 2,000 4,000 10,000 28,000 60,000 100,000 200,000 0.14 0.28 0.56 1.40 3.92 8.40 14.00 28.00 0.21 0.42 0.84 2.10 5.88 10.60 21.00 42.00 0.42 0.84 1.68 4.20 11.76 21.20 42.00 84.00 Storage for hourly Max. rate poak for fire protection <20% of max. day) (mod) (mil gal) 1.44 2.16 2.88 4.32 7.20 10.08 12.% 17.28 0.04 0.08 0.13 0.42 1.17 2.12 4.20 8.40 M 4 | WATER AND WASTES ENGINEERING CTD000Q89 Materials Asbestos-cement Cast iron (cement-lined) Cast iron (ductile) (cement-lined) Concrete (reinforced) Concrete (prestressed) Steel Dlam. (In.) 4-36 448 4-30 12-168 16-120 4-120 TABLE *--TRANSMISSION AND DISTRIBUTION PIPELINE MATERIALS Normal max. workln pressure (p*o 200 Advantages Corrosion resistant; good flow charac teristics; light weight; easy handling; low maintenance Disadvantages Low flexural strength in small sizes; more subject to impact damage; diffi cult to locate underground 350 Durable and strong; good corrosion re Subject to electrolysis and attack from sistance; easily tapped; flow charac acid and alkali soils; heavy to handle teristics good 350 Durable, strong, high flexural strength; Similar to cast iron lighter weight than cast iron; greater carrying capacity for same external di ameter; fracture resistant; easily tapped 50 Durable with low maintenance; good May deteriorate in alkali or soil, if ce corrosion resistance; flow character ment type is improper, or in acid soil if istics good; resists backfill and external not protected loads 250 Durable, low maintenance; good corro Same as above sion resistance; good flow character istics; resists backfill and external loads High light weight and easily installed; high tensile strength; low cost; good hy draulically when lined; adapted to loca tions where some movement may occur Subject to electrolysis; external corro sion in acid or alkali soil; poor corrosion resistance unless properly lined, coated, and wrapped; low resistance to external pressure in larger sizes; air- vacuum valves imperative large sizes; subject to tuberculation when unlined TABLE 4--AWWA STANDARDS FOR WATER PIPE Pip material Asbestos-cement Cast iron Concrete Ductile iron Steel AWWA Standard no. C 400-65, H2-64 H 1-67, C 104-64, C 106-62, C108-62, C 110-64, C 111-64, C112-65 C 300-64, C 301-64, C 302-64, H 3-65, C 151-65 C 201-60T, C 202-64T, C 207-55, C 208-59 High service systems. Separate distribution systems that serve areas on high ground or where high pressure require ments exist are called high service systems. Valve system. Shut-off valves should be provided to sectionalize the distribution system. The sections should be laid out so that most of the flow will be maintained if any one section is cut out of service. Valves for sectionalizing pur poses should be spaced at 1200 ft intervals and at all branches from arterial mains. Where line intersections exist in a grid, no more than one branch, preferably none, should be without a valve. (Note: valve and hydrant selection, installation, and operation will be covered in Manual of Practice No. 4.) Where cross con nections are made between an industrial and domestic sup ply, the connection must be by a backflow preventer that has state health department approval. System planning Information required for distribution system planning and operation includes a topographic map of the area served, location of other utilities, maps of the system, and quantity and pressure requirements. Maps. A topographic map (400 ft to the inch) should show the following information for the entire system: The existing system Present and planned streets Areas outside the system (possible future expansion) Ground level elevations and contours Streams, grade changes, topographic features Installed utility lines including sewers, storm drains. gas and steam lines, and underground electric and telephone cables Population densities in different areas Normal water consumption by areas Pressure at strategic points Sectional maps, usually 24 by 36 in., scaled 50 or 100 ft to the inch, should be drawn for the entire system and should show complete details including valve and hydrant locations. Maps scaled at 20 ft to the inch may be desirable for intersections or congested areas. Distribution system record books should be keyed to the sectional maps. Layout. Distribtuion system layout may be designed to fit one of three configurations or a combination. Loop. A complete loop, or belt, of arterial mains around the area, with branches projecting inward to serve the dis tributors (see Fig. 1). Gridiron. All ends of distributor mains are connected to eliminate dead ends (see Fig. 2). This arrangement may be come a loop system or it may be a single arterial main through the area, with the branches looped. Tree. This arrangement consists of a single arterial main that decreases in size with length. Branches are taken off at right angles, with sub-branches from each branch. Growth planning. System planning must include a long range program for distribution system growth. This pro gram should include regular revisions of growth charts showing population data and average- and maximum-day pumpage plotted against years. Projection of these data should be made each year for 10 years hence. The projected data should include population growth and domestic water usage and also expected growth of commercial and indus trial water usage. In large cities, such future projections and planning should be made for important growth areas within the community. Sizing mains The size of a main is a measure of its carrying capacity, and sizes must be selected to provide the flow (capacity) to meet domestic, commercial, and industrial demands plus the fire flow required under the maximum-day demand conditions and pressure required in the area to be served. CTD000090 MAY 1967 | M 5 DIST RIBUTION MAIN \ ART ;rial fIAAIN-____ k TRANSMISSION LINES Fig. 1. Arterial loop system. These capacity criteria should be for the needs anticipated 25 years hence. Minimum pipe sizes. No main in a distribution system should be less than 6 in. in diameter, a limitation suggested by the American Insurance Association. For sound design, it is desirable to select the next size larger than that indicat ed by calculations of pipe size required. The American Insurance Association further recommends that minimum pipe sizes should be governed in part by the type of area served, for example: High value districts should have minimum pipe sizes of 12 and 8 in.; residential areas should have minimum sizes of 8 and 6 in. The smaller sizes should be used only when they complete a good grid. Quantity requirements. Domestic usage requirements for any service area should be based on the data in Table 1, ad justed for commercial and industrial factors and population growth factors. Fire flow requirements should be based on Eq. 1, and the conditions set forth by the AIA.2 AIA has set required fire flow (in gpm) for cities of 1000 to 200,000 population and the hours of duration that this flow must be maintained in these various city sizes.2 In residential districts, the fire flow is determined on the basis of structural conditions and congestion of buildings.2 TABLE S--TYPE OF RESIDENTIAL AREA VS. FIRE FLOW REQUIRED Area description One-third of the tots have buildings of low height and small area Buildings of larger area or greater height Closely built, or high value residences, apartments, etc. Densely-built districts with 3-story or higher buildings Flow required (gpm) 500 1000 1500-3000 6000 M 6 | WATER AND WASTES ENGINEERING Fig. 2. Grid type of distribution system. In this respect, AIA sets the limitations shown in Table 5. Pressure requirements. Minimum static pressure at all fire hydrants should be 30 psi; pressure should be higher in areas requiring high fire-flow capacity. Pressures at con sumers' residences should be at least 20 psi, preferably 30 psi. For buildings up to ten stories, the pressure should be 50-65 psi. Flow capacity. Pipe-carrying capacity depends on pipe size, pressure, flow velocity, and head loss resulting from friction. Friction factors include roughness of pipe and Reynolds Number, which depends on flow velocity and pipe diameter. The required pipe size is calculated from required flow (in gpm), head loss for pipe length desired, and flow veloci ty. The Hazen-Williams formula (Eq. 2) is: V = 1.318 CR 03 s054 Eq. 2 where V = flow velocity (fps) C = Roughness coefficient R = 'hydraulic radius of pipe (ft) s = hydraulic gradient (ft per 1000 ft) The applications of this formula has been simplified by the use of a special slide rule (Fig. 3).* Nomograms, for solving the Hazen-Williams formula, may be used in place of the slide rule.** A number of these published nomograms are listed in a reference work on nomograms.5 Also useful are charts based on the Hazen-Williams formula for differ- * This slide rule may be obtained, free, from The Cast Iron Pipe Research Assn., Chicago, IU., or from the Gnnnell Co., Providence, R. I., Interpace Pipe Div., Parsippany, N. J., American Concrete Pipe Assn., Chicago, III., and CertainTeed Products Corp., Ambler, Pa. Available from Johns-Manville, New York, N. Y. CTD000091 Fig. 3. Hazen-Williams slide rule. Inplant piping system in pump station. ent pipe sizes.0 Useful tables of cast iron pipe based on the Hazen-Williams formula have been published for various pipe sizes and various C-values.1 Table 6 lists C-values of new pipe of various materials and age. In making flow calculations for pipe line design, it is good practice to use C-values shown in Table 7. For old lines, these values should be reduced. TABLE (--C-VALUES OF VARIOUS PIPE MATERIALS Pipe material C-value Asbestos-cement 140+ Cast iron (new) 140+ Bitumastic enamel, centrifugally applied 140+ Cement-lined, centrifugal method,actual diameter 140+ Pit cast, tar dipped 140 Cast iron (20 years old) 100 Tar dipped (inactive water) 130 Bitumastic enamel (inactive water) 135 Cement lined 140 Tuberculated 100* Concrete (quality pipe) 140+ Ductile iron (cement lined)** 1404- Plastic 1404- Steel 140+ Wood stave (smooth) 120 * Less with high degree of tuberculation ** Greater capacity because of larger internal diameter tor normal out side diameters. TABLE 7--PREFERRED C-VALUES FOR FLOW CALCULATIONS Type of lino Transmission lines Arterial mains Distribution mains Old New C-value 140* 130 120 100 *ln the absence of growths. System analysis. Where the distribution is extensive, it is necessary to analyze the system and balance the flow among all areis in relation to demand. This computation involves determination of the take-off quantity from the arterial mains to the various branches and sub-branches and deter mination of the hydraulic grade line of the system. In short, this analysis requires a plot of the pressures and flows at points throughout the system. There are five principal methods for system analysis: Electric network analyzer, Hardy-Cross method, equivalentpipe method, graphical method, and uncontrolled trial and error. It is also possible to construct a hydraulic model, but this method is exacting and expensive. The electric network analyzer is most useful, but the equipment is expensive, unless it can be used for continuous updating of the system. The Hardy-Cross method8 involves many calculations, but the time-consuming operations can be reduced by the use of a computer. The equivalent-pipe method technique0 offers a simpli fied, yet effective approach to distribution system analysis. Materials The selection of materials for distribution mains should be based on the same criteria that are used for transmission lines; see above and Tables 4 and 6. In addition to meeting these criteria, distribution mains must also be easily tapped. Corrosion protection and maintenance of flow conditions are also important; see Part 2. Installation. Criteria for installation procedures and methods of installation are covered in Part 3. Section 3--Services Services or service lines are pipes of small diameter that run from distributor mains or branch mains to customers' premises. Materials The selection of service line material is influenced by the following factors: size, durability, water characteristics, cor rosion resistance, availability, ease of installation, mainte nance, and economics. All of these factors should be taken into consideration before materials are selected. Types of material. Lead was probably the earliest materi al used for service lines. (It was used in Rome about 300 B.C.) This metal is no longer popular for service lines be cause of its cost and its tendency to dissolve in soft waters at low pH. Copper is now the most popular service line material. Approximately half the water utilities in the United States use copper exclusively, and most of the other half use more copper than other materials. Plastic pipe has gained in pop ularity for service line use; as its formulations improved, ap plication experience grew. Several types of material are available for service line use, including a number of plastics. Plastic pipe selected for potable waters should meet ap proved specifications and should carry the seal of approval of the National Sanitation Foundation. Sizing services Modern practice must take into account the customer de mands including peak-hour demands for lawn sprinkling, dish-washing, laundering, and other household uses. Minimum service-line size should be 3/4 in., preferably 1 in. For large residences with many baths and large lawns, service lines should be 1-1/4 or 1-1/2 in. Multiple dwelling buildings require larger services. The City of Richmond, Va., relates service-line size to number of fixtures, or combi nations of fixtures, together with flow in meters of different sizes, through the use of tables and charts.10 CTD000092 MAY 1967 | M 7 Usa Air lines Chemical feeding Filter piping Gas lines Heating systems High service Low service Plumbing Pump discharge Pump suction Sampling lines Wash water system Asbestoscement V V V V V V V V V V Cast Iron V V .V V V V V V V V V V TABLE l--IMPLANT PIPING MATERIALS Concrete Galvanized Copper Iron Glass VVV V VV V V VV VV V V V V V VVV V Plastic V V V V V V V Rubber V V V Steal V V V V V V V V V V V V Wrought iron V V V V V V V V V V Rule-of-thumb is not good practice for determining the size of service lines. It is necessary to consider not only the customer demands as estimated from an analysis of fixtures and other factors such as lawn sprinkling, but also the ex pected hydraulic losses. These losses can be relatively high, as indicated by the following data. For a 3/4-in. copper service line 40-ft long and a 5/8-in. meter, the hydraulic friction loss at a flow of 10 gpm is approximately 13 psi. If 30 psi is available at the main, such a loss would leave only 17 psi of head at the house to overcome static head from basement to top floor and fric tion loss in the plumbing system. This pressure is insuffi cient for good service. A 1-in. line would have a friction loss of only 5.5 psi for the same installation. Some indication of the range of hydraulic friction losses is shown in the following data on 1/2- and 3/4-in. service lines. Flow rate (gpm) 1 10 20-ft line 1/2-in. 3/4-in. 0.28 0.19 15.6 10.73 Friction loss (psi) 100-ft line 1/2-in. 3/4-in. 1.4 0.4 78 22.7 These data show clearly why small service lines should not be used. Complete tables and curves for hydraulic fric tion losses have been published by the American Water Works Association.7 Location and ownership In rapidly growing areas, taps may be made and corpora tion cocks installed on mains as they are laid, with the ser vices spaced according to lot width. About half the water utilities in this country follow this practice, but there are sound reasons for not doing so. The principal objections to this practice are: the service line may be the wrong size or poorly spaced when the area is developed; there is a possi bility that many connections will not be used; and such ser vices are possible sources of leakage. About half of all services are owned by the utility and half by the customer, but utilities install approximately twothirds of all services (about 20 percent are charged to the customer). When services must be replaced before street re surfacing or installation of permanent pavement, the cost is borne by the utility about 70 percent of the time. Installation Criteria for installation procedures are covered in Part 3. Section A--Inplant Piping Inplant piping systems include pipes and piping in pump stations, treatment plants and filter galleries. Design Factors important in the design of inplant piping systems include: use (application or service), material selection. M 8 | WATER AND WASTES ENGINEERING size, pressure, flow capacity, and layout and arrangement. The selection of pipe size and material will depend on the required flow capacity and working pressure of the fluid to be handled. Material selection Table 8 lists various uses or systems and types of pipe generally suitable for use. Final selection of the material must include all factors listed above. Layout and arrangement Whatever the particular service of the system, piping should always be arranged to provide a minimum interrup tion of service as a result of any one piping break or outage. This rule is particularly applicable to low and high service lines and suction and discharge headers. Layout of piping and valves should be systematic and should conform to the placement of pumps and other equip ment, with a minimum of bends and fittings so that head loss is held to a minimum. Piping arrangements should provide for easy access to pumps, valves, and other equipment during installation or maintenance procedures. Suction piping, in particular, should be carefully designed to avoid air pockets. These lines should rise gradually to the pump. Eccentric reducers should be used to prevent the for mation of air pockets. Color coding It is highly desirable to color code all pipe lines in every inplant piping system. A standard color-code system11 has been developed by the U. S. A. Standards Institute (former ly the American Standards Association). Most water plant designers and managers prefer some variations of this stand ard system. Whatever the colors selected, they should be easily recognized. Include the following items in the lines to be color-coded: Air lines Chemical feed lines (color code each chemical) Chemical feeder waste lines Filter lines Gas lines Heating systems High service (finished water) Low service (raw water) Potable water systems Plumbing waste line (sewers) Sampling lines Washwater system Color-coding systems may employ solid colors, or solid colors plus distinctive bands, and lettered labels at points where the information is desirable. Directional arrows on all lines are also desirable. The colors and shades should be easily visible and recognizable in the light available at all locations. CTD000093 water and wastes / engineering / MANUAL OF PRACTICE NUMBER TWO WATER SYSTEMS pipes and piping PART 2/ PIPE MATERIALS For use in transmission and distribution systems, pipe materials must have certain characteristics: Ability to withstand internal pressure and external load Ample tensile strength Resistance to beam load failure Maximum flow capacity for particular pipe size Resistance to aggressive soils and waters Long life, toughness, imperviousness, ease of tapping, and tight joints The following sections discuss various types of pipe mate rial including design and manufacture, pipe sizes, testing, protective coatings, joints, and shipping. Section 1--Asbestos-Cement Pipe The ingredients used to make asbestos-cement pipe are simple: asbestos fibers, silica sand, and cement. Although asbestos fibers make up the smallest percentage of the total volume of pipe material ingredients, their high tensile properties add significantly to the overall pipe strength. Asbestos is a mineral fiber produced by extreme geologi cal pressures during the formation of the earth's crust and is found in many countries. It is both strong and silky. Three types occur: chrysotile, amosite, and crocidolite. Most of the asbestos used in this country comes from Canada and South Africa. Design Asbestos-cement pipe was first made in Europe in 1913, and it was introduced into this country in 1929. As a water pipe, it is designed to meet the conditions of installation and service. Factors of design. Pipe strength design is determined by consideration of these factors: internal pressure, external load, and safety. The method for selecting the pipe-wall thickness is set forth in detail in AWWA Handbook H-2 entitled "Standard Fig. 5. Three-edge bearing test for A-C pipe. W represents load; R, approximately 0.5 in., the radius of the bearings; D, the nominal diameter of the pipe; and C, the clear space between wooden supports. C should be 0.5 in. for diameters of 12 in. and under, 1 in. for 14 to 24 in. inclusive, and 2 in. for 30 in. and over. Practice for the Selection of Asbestos-Cement Water Pipe.''12 The following paragraphs describe the method. Combined loading. The relationship between the com bined effect of internal hydrostatic pressure and external loads is represented by an empirical parabolic curve (Fig. 4) and the following equation: w = W yp ~ P P Eq. 3 where w = external load at which the pipe will fracture in combination with internal pressure p (lb per lin ft)* W = crushing load of pipe in a three-edge bearing test, with no internal pressure (lb per lin ft) p = internal pressure at which pipe will fracture in combination with external load w* (psi) P = bursting pressure of pipe when no external load exists (psi) * Three-edge bearing test, see accompanying description. Three-edge bearing load. The usual method for determin ing the crushing strength (W) is the three-edge bearing test (Fig. 5). It is necessary to adjust the value obtained from CTD000094 MAY 1967 | M 9 where W-, = load on the pipe (lb per lin ft) P = concentrated load on pipe (lb) F = impact factor due to dynamic load of mov ing vehicles (see Table 10) C< = load coefficient* L = effective length of pipe (ft); use 3 ft for pipe lengths greater than 3 ft and actual length for lengths less than 3 ft * Load coefficient is a function of Bt/2H and L/2H; where B, is pipe diameter (ft). H is distance from ground surface to top of pipe (ft), and L is effective pipe length (ft) (data for these values may be obtained from tables in AWWA Handbook H-2).1S Manufacture of asbestos-cement pipe. this test to field conditions because of the supporting strength of the installation conditions. Therefore, a load factor is applied to the three-edge bearing loads to correlate them to field loads. In this relationship, the value is ex pressed as the external load calculated by multiplying the three-edge bearing load by the bedding conditions load fac tor. Table 9 shows typical field installation conditions and the load factor for various pipe sizes. TABLE I--RELATION OF IEDDIN6 CONDITIONS, PIPE SIZE, AND L0A0 FACTORS FOR ASBESTOS-CEMENT PIPE Bedding condition (class) Description Pipe size (in.) Load factor A Gravel or sand base: backfill tamped 4-12 1.7 14-20 1.8 24-36 2.0 B Same as A; but backfill not tamped 4-36 1.5 C Pipe laid on earth mounds or pipe 4-12 1.3 barrel on flat trench bottom with ex 14-20 1.4 cavated coupling holes; backfill 24-36 1.5 tamped D Same as C; but backfill not tamped 4-36 1.1 External loads. Two factors contribute to external loads on pipe: backfill and superimposed loads (either static or moving, or both). Gravity earth loads are computed on the theory13 that the load on a buried conduit is equal to the weight of a prism of earth (interior prism) directly over the pipe, plus or minus frictional shearing forces transferred to that prism from adjacent prisms of earth. The general equation for this theory is: W = CwB! Eq. 4 where W w B C vertical load on conduit due to earth load (lb per lin ft) weight of earth (lb per cu ft) trench width or pipe outside diameter depend ing on installation conditions (ft) coefficient consisting of four factors: (1) ratio of fill height to trench or conduit width (2) shearing force between interior and ad jacent earth prisms (3) direction and amount of relative settle ment between interior and adjacent earth prisms for embankment conditions (4) rigidity of conduit support for embank ment conditions Superimposed loads are determined by this equation: Wbc Eq. 5 M 10 | WATER AND WASTES ENGINEERING TABLE II--IMPACT FACTORS DUE TO MOVING VEHICLES (FOR ASBESTOS-CEMENT PIPE) Type of traffic Highway Railway Airfield runways Airfield taxi ways, aprons mpact factor (F) 1.50 1.75 1.00 1.50 Internal pressure. Possible hydrostatic pressure within the pipe results from a combination of operating pressure and surge pressures. Operating pressures are determined from the service provided. For normal service installations, a safety factor of 4.0 is applied to operating pressure in the combined internal-external loading calculation, which is more than adequate for most surge conditions. For excep tional surge conditions, water hammer allowance is calcu lated by special equations (see AWWA Handbook H-2).12 Safety factor. In developing the selection curves,12 a safety factor of 4.0 was applied to internal pressures and a factor of 2.5 to external loads. Pipe selected from the curves12 will have a safety factor of 2.5 for internal pres sure when combined with a safety factor of 2.5 for an exter nal loading of the normal earth load plus a 10,000-lb wheel and impact load. Pipe classes. According to AWWA Standard C400-65,14 asbestos-cement pipe intended for water service is manufac tured in three classes: Class 100, Class 150, and Class 200; to be used respectively for operating pressures of 100, 150, and 200 psi. Detailed requirements for this type of pipe, set forth in the AWWA Standard,14 will be discussed in the paragraphs under the topic "Manufacture." Selection curves. From calculations of the combined loading factors for different laying conditions, pressures, external loads, etc., a set of selection curves for asbestos-ce ment pipe have been published in the AWWA Handbook H-2.12 Two of these sets of curves are shown in Fig. 6. Thickness and surfaces. The AWWA Standard C400- 6514 requires the wall thickness of the machined portion of any length of pipe to be within 0.08 in. of the manufactur er's standard, for pipes with a wall thickness of 1 in. or less, and within O .'O in., for pipes with a wall thickness greater than 1 in. The standards also require the inside of each pipe to be free from bulges, dents, and tears that could cause a varia tion of more than 0.2 in. from the diameter of adjacent areas. Couplings must be free of dents and gouges. Flaking of the exterior surface and edge of machined ends may not extend back more than 0.50 in. from the end, or have a depth of more than 0.125 in., and may not extend more than 0.50 in. around the perimeter at any point. Manufacture The manufacture of asbestos-cement pipe begins with the opening of the natural "bundles" of fibers. The individual strands are spread apart to develop the ultimate strength of the fiber. The fibers, finer than human hair, are placed in a f CTD000095 DESIGN EXTERNAL LOAD (ib/lin ft) 0 1000 4000 MOO 1000 10,000 DESIGN EXTERNAL LOAD (ib/lin It) 0 2000 4000 6000 1000 10,000 zo o Fig. 6. Examples of A-C pipe selection curves. special machine for the bundle-opening operation and are cleaned electromagnetically to remove any iron compounds, which are frequently associated with asbestos deposits. Materials. Besides the asbestos fiber, asbestos-cement is composed of portland cement, or portland blast furnace slag cement, or portland pozzolana cement, and silica. The amount of each used varies but is usually in the following ranges: asbestos, 15 to 20 percent; silica, 32 to 34 percent; and cement, 48 to 51 percent. Process. After the asbestos is milled and cleaned, the var ious types of fibers are blended and stored in hopper bins. The portland cement and finely ground silica are also stored in bins. The ingredients are weighed automatically in the proportional amounts and discharged to a series of blend ers, where they are physically and thoroughly mixed. To this mixture is added a metered amount of water, and a slurry is produced for transport to the pipe-making ma chines. Pipe production. The following brief description of pipe manufacture is based on the material in Section V of "Sew ers for Growing America."16 The slurry is discharged into vats in which are located long revolving drums covered with a fine-mesh screen. The solid mixture deposits as a thin film on the screen, and water drains through as the drums rotate. The rotating drum carries the film to a point where it makes contact with a moving felt. The thin continuous sheet is transferred to the felt, which moves the film to the next step. The drum length and felt width are slightly more than the finished pipe length. The film and felt pass over a vacuum box, where excess water is removed, and then come in contact with a rotating, smoothly-polished, heavy-walled steel mandrel. As the felt and mandrel make contact, the thin film is continuously de posited on the mandrel until the desired pipe thickness is obtained. Hydraulic pressures on the felt compress the as bestos-cement mixture into a uniform, homogeneous solid with low water-content and high density. Heat drying. When the desired wall thickness has been reached, the mandrel and pipe are taken out of the pipe forming machine and placed in a heat chamber where the pipe wall sets. The mandrel is removed from inside the pipe, and the pipe is subjected to additional heat to increase the strength, rigidity, and stability for further inplant handling. Curing. AsbestosTcement pipe is cured by subjecting it to high-pressure steam in an autoclave. The purpose of the curing process is to reduce the content of uncombined calci um hydroxide that results from the curing of the portland cement mixes. The calcium hydroxide content is reduced to less than 0.5 percent. The result is a more stable and chemically-resistant cementing compound produced by reaction of the calcium hydroxide with the pulverized silica. Steam curing lasts 10 to 12 hr, after which the pipe is removed from the autoclave and trimmed to the standard length of 13 ft. Each pipe end is then machined to accept the cou pling unit. Couplings are produced in the same manner as pipe. Testing In accordance with AWWA Standard C400-65,14 as bestos-cement pipe for use in water lines is subjected to tests to ensure its proper service. All pipe and couplings are test ed in a normal air-dried condition. Hydrostatic test Every length of pipe is subjected to a hydrostatic test for a period of 5 sec. Test pressure are: 350 (Class 100); 525 (Class 150); and 700 psi (Class 200). All air is expelled from the pipe and the pressure increased at a uniform rate of not less than 100 psi per sec. From each 300 standard lengths of each size and class, one length is tested at pressures of four times the operating pressure for that class. CTD000096 MAY 1967 | M 11 Cement-mortar coating being added to steel pipe. Flexure test. Each pipe length of 4-, 6-, or 8-in. diam. pipe is tested for flexure for 5 sec, with the load applied at a minimum rate of 500 lb per sec. The pipe is placed on bear ing points 9 or 12 ft apart, depending on the pipe length. Pressure is applied at third points of the pipe length, onehalf of the total pressure being applied at each point. The total load applied for each pipe class is shown in Table 11. Each pipe must support the loads noted in Table 11 with no evidence of cracks or other defects. TABLE 11--FLEXURAL TEST LOADS FOR ASBESTOS-CEMENT PIPE Pipe size (in.) 4 6 8 Total applied load (psi) Class 100 1200 2800 5330 Class ISO 1460 3700 7600 Class 200 1860 4900 10130 Crushing test One length of pipe out of each 300 lengths of each size and class (or each lot of 100 if less than 300 in a lot) is subjected to a crushing test. A 12-in. specimen is cut from the unmachined section of the pipe and is placed on a two-edge bearing support (the distance between sup ports being determined by the pipe size),14 and the load is applied along the full length of the specimen. After 75 percent of the total load is applied, the loading is increased at a uniform rate of 2000 lb per min. An ac ceptable test allows failure only after the total load applied exceeds the values given in Table 12. Rejection. When pipe test specimens fail to withstand 75 percent of the crushing load given in Table 12, the entire lot is discarded. When specimens fail between 75 and 100 per cent of the crushing test values in Table 12, tests are made on two additional specimens. If these do not meet the re quirements of Table 12, the entire lot of pipe is rejected. Uncombined calcium hydroxide. Purchasers may specify a limit for uncombined calcium hydroxide. A standard test procedure utilizes phenolphthalein indicator, glycerol-etha nol solvent, and standard ammonium acetate solution,14 and the results are reported as the percent of uncombined calcium hydroxide by weight. Surface characteristics By virtue of its method of manufacture, asbestos-cement pipe is smooth on the outside, and due to the polished man drel used in its formation, it normally has a very smooth in terior bore. Therefore no coatings of any kind are used. Because of its chemical composition, the pipe is unaffect ed by corrosive water or soils. With its smooth bore, it has a high C value at installation, a value that remains high throughout use. The low content of uncombined calcium hydroxide ensures that the leaching effects of soft waters will be at a minimum. Pipe sizes Asbestos-cement water pipe is supplied in standard sizes in each class as follows: 4, 6, 8, 10, J 2, 14, 16, 18, 20, 24, 30, and 36 in. The average inside diameter of a standard or random pipe length may not be less than the nominal diam eter by more than 5 percent for sizes through 16 in., and 1.5 percent for sizes 18 in. and above. Joints Asbestos-cement pipe lengths are joined by special cou plings, also made of asbestos-cement. These couplings, somewhat larger than the outside diameter of the pipe, are machined to fit over the machined ends of the pipe. Two flexible rubber O-rings are placed within the coupling prop er and make a water tight seal. These joints also provide some degree of flexibility in laying the pipe without leakage. Figure 7 shows a coupling for asbestos-cement pipe. Shipping Asbestos-cement pipe and couplings are marked with the manufacturer's name and a "T" to indicate that the pipe has been hydrostatically tested. Rubber jointing rings are marked for identification with size, year, and class of pipe with which it is to be used. The pipe is carefully handled, palletized, and loaded on trucks or railroad cars and tied down to prevent damage in transit. Installation and handling procedures are covered in Part 3. TABLE IT--CRUSHING TEST LOADS FOR ASBESTOS-CEMENT PIPE siza (In.) 4 6 8 10 12 14 16 18 20 24 30 36 Load applied (Ib/lln ft) Class 100 Class ISO 4,100 5,400 4,000 5,400 4,000 5,500 4,400 5,200 7,000 7,600 5,200 5,800 8,600 9,200 6,500 7,100 8,100 9,700 11,200 10,100 10,900 12,700 15,900 19,600 Class 200 8,700 9,000 9,300 11,000 11,800 13,500 15,400 17,400 19,400 22,600 28,400 33,800 M 12 | WATER AND WASTES ENGINEERING Fig. 7. Coupling for A-C pipe. CTD000097 Section 2--Cast Iron Pipe Design There are two types of cast iron available for water pip ing systems: gray cast iron and ductile iron. Gray cast iron has a history of use that dates back more than 300 years. Ductile iron was developed in 1948, and its use has been in creasing since 1960. Gray cast iron. The characteristics of long life, toughness, imperviousness, and ease of tapping are provided in gray cast iron by the chemical composition of the metal, and carrying capacity is ensured by proper lining. (See discus sion on manufacture.) The ability of pipe to withstand in ternal pressure and external load are matters of design of strength and thickness of the pipe. Factors of design. Five factors determine pipe design: in ternal pressure, external load, safety, allowance for corro sion, and foundry tolerance. The method for calculating pipe wall thickness and strength for different pipe sizes and installation and operat ing conditions is generally termed the "American Standard Method of Design." A brief description here will serve to acquaint the reader with the fundamental principles of the method, details of which are set forth in AWWA Handbook H-l, entitled "American Standard for Thickness Design of Cast Iron Pipe."16 This empirical method of cast iron pipe design, based on a series of intensive research studies, provides the means whereby required barrel thickness can be established for use in any reasonable combination of internal pressure and ex ternal loads. The empirical relationship for the combination of external load and internal pressure at which a pipe will fail is shown in Fig. 4. The y-axis intercept of this curve represents the external breaking load (W), when no internal pressure exists. The xaxis intercept represents the bursting pressure (P), when there is no external load on the pipe. This load pressure curve is the basis of the system of barrel thickness computa tion, and the equation of this load-pressure parabola is ex pressed by this formula: W _____ w = -^= VP - p Eq. 6 where w = external load at which the pipe will fracture in combination with internal pressure p (lb per lin ft) W = crushing load in three-edge bearing, with no in ternal pressure (lb per lin ft) p = internal pressure at which pipe will fracture in combination with external load w (psi) P = bursting pressure of pipe with no external load (psi) BACKFILL NOT TAMPED Fig. 9. Types of trench bottoms. FLAT BOTTOM TRENCH BACKFILL TAMPED The value of P is determined from Eq. 7. P 2tS d Eq. 7 where t = pipe thickness (in.) S = bursting strength from full length bursting test (psi) d = internal diameter of pipe (in.) The value of W (lb per lin ft of pipe supported in threeedge bearing) is given by the following equation: t*R W= 0.0795 (d + t) Eq. 8 where W = crushing load (lb per lin ft) R = modulus of rupture of the metal (psi) d = internal diameter (in.) t = wall thickness (in.) Modulus of rupture is determined from crushing tests in the three-edge bearing test (see Fig. 8), with the pressure applied at the top bearing uniformly along the full specimen length. R values of 40,000 or 45,000 are stand:.' d for gray cast iron. This test is a convenient means for computing field conditions. External loads. The external load on a pipe consists of two factors: weight of backfill and weight of traffic plus im pact. The load-carrying capacity of a pipe is influenced by the laying conditions (see Fig. 9). The best method of laying pipe is the one that provides the highest load factor. The most common methods used and their load factors for 12-in. pipe are: A--Flat bottom trench, backfill not tamped (1.15) B--Flat bottom trench, backfill tamped (1.38) Where greater load capacity is desired, the pipe may be bedded in gravel or sand, with backfill tamped (load factor 1.85). CTD000098 MAY 1967 | M 13 Hydrostatic testing of wrought iron pipe. All other types of pipe are hydrostatically tested in similar manner. Continuous weld wrought iron pipe is formed from skelp. Internal pressure. Internal pressure consists of two com ponents: normal working pressure and water hammer. The former is readily ascertained, but water hammer, caused by rapidly closing valves or stopping centrifugal pumps, may vary widely. An allowance of 70 to 120 psi is made, de pending on pipe size. (See Table 13.) TABLE II--ALLOWANCES FOR WATER HAMMER Pip* size (in.) 4-10 12-14 16-18 20 24 30 36 42-48 Water Hammer (psi) 120 110 100 90 85 80 75 70 Design calculation. To determine the required barrel thickness, the calculation is made for two conditions: Case 1--normal working pressure plus backfill and traffic loads; Case 2--normal working pressure plus water hammer and backfill load. The thickness selected is the greater of these two values obtained from the calculations. There are eight steps in the calculation, as illustrated by the following example for the determination of the thick ness of a 16-in. gray cast iron pipe for a normal working pressure of 150 psi, installed with laying condition B in a trench of width (d + 2) ft and under 5 ft of earth cover. Step 1: Determine earth fill load for the laying condition, trench width, and depth of cover. (Diagrams and tables are given in AWWA Handbook H-l.)1 Divide the earth fill load by load factor for laying condition and pipe size, mul tiply by a 2.5 factor of safety. This is w for Case 1. w 1470 Ib/ft X 215 = 2570 lb/ft 1.43 Step 2: Calculate truck load for two passing 18,000-lb axles with inboard wheels 3 ft apart. (Refer to diagrams and tables in AWWA Handbook H-l.)16 Adjust values ac cording to laying condition and pipe size. Increase the truck load by 50 percent for impact. Add the truck load to the earth fill load, divide the sum by the load factor, and multi ply by a 2.5 factor of safety. This is w for Case 2. w 1.50(393) + 1470 1.43 X 2.5 = 3600 lb/ft Step 3: Add water hammer allowance (Table 13) to the normal working pressure and multiply the sum by a 2.5 fac tor of safety. This is p for Case 1. p - (150 + 100) 2.5 = 625 psi Step 4: Multiply the normal working pressure by a 2.5 factor of safety. This is p for Case 2. p = 150 X 2.5 = 375 psi Step 5: For Case 1, with w -- 2570 lb per ft and p = 625 psi, use the appropriate nomograph in AWWA Hand book H-l,1 select a net thickness for 16-in. pipe of 0.39 in. Step 6: For Case 2, with w - 3,600 lb per ft and p = 375 psi, the required net thickness would be 0.38 in. Step 7: To the greater of the two thickness values ob tained in Steps 5 and 6, add a foundry tolerance (see table in AWWA Handbook H-l)1 and a corrosion allowance of 0.08 in. to obtain the calculated thickness. t = (0.39 + 0.08 0.08) = 0.55 in. Step 5: Refer to the table of Standard Thickness Classes in AWWA Handbook H-l,1 and select the thickness nearest the calculated thickness of Step 7. For the 16-in. pipe of the problem, select Class 22. Nomographs and charts are available from which it is possible to read directly the total thickness for conditions A and B and to make all the necessary calculations. Pipe classes. Cast iron pipe is not made in every diameter or in incremental thickness of 0.01 in.,.but it is available in standard manufacturing thickness classes. These classes are separated in weight by incremental increases of 8 percent. From these tables of standard classes, the pipe designer chooses the pipe class that gives the wall thickness nearest to that calculated as above. (See AWWA Handbook H-l.)1 Ductile-iron pipe. This type of pipe is stronger, tougher, and more ductile than gray cast iron. Its characteristics are due to the configuration of the free carbon or graphite in the iron. The method for t.' ckness design of ductile iron pipe is presented in AWWA Handbook H3-65.17 The method is based on flexible-pipe principles and the characteristics that distinguish flexible pipe from rigid pipe. Particular consid eration is given to the reduction in bending stress from trench load by lateral soil reaction; the rerounding effect of internal pressure on the initial deflection resulting from trench load; and the fact that flexible pipe, in deflecting under earth load, transfers a significant part of the load to the side fill soil columns. Thickness selection. The required wall thickness for duc tile iron pipe is determined as the larger of the net values determined separately for external load (bending stress) and internal pressure (hoop stress). To this net thickness is added a corrosion allowance and a casting tolerance. The M 14 I WATER AND WASTES ENGINEERING CTD000099 Prestressing concrete pipe. final thickness for specifying and ordering is selected from a table of standard thickness classes.17 Steps in calculation. The directions for selecting the re quired pipe thickness are as follows: Step I: Design for trench load and the usual field condi tions (A and B as for cast iron). Use tables in AWWA Handbook H3-6517 to determine the trench load per linear foot and the earth load and truck super load that is applica ble; then proceed with the calculation for the conditions in volved. Step 2: Design for internal pressure using this equation for hoop stress: where t = net wall thickness (in.) p = working pressure plus surge pressure (psi) D = outside/diameter (in.) s = design hoop stress (psi) Step 3: Select the larger of the two values from Steps 1 and 2. To this figure add a corrosion allowance of 0.08 in. and a foundry tolerance. The foundry tolerance will vary from 0.05 in. (for 3- to 8-in. pipe) to 0.08 in. (for 48-in. pipe). Step 4: Select the standard thickness class that equals the value obtained in Step 3. If the calculated value falls be tween two classes, select the larger class size. If the calcu lated thickness is less than the smallest standard class, select the smallest standard class. Manufacture The production of cast iron pipe begins with the melting of the metal in a furnace (cupola) and the addition of such other materials as contribute to final desired composition. Gray cast iron pipe. Charges of iron, scrap, coke, and limestone are carefully weighed and proportioned to give the desired chemical composition to the iron. As the molten iron is withdrawn from the cupola to a ladle, small amounts of graphite and fei ,'osilicon are added to adjust the carbon and silicon content; this is termed inoculation. The amounts of carbon, silicon, manganese, etc., although small, mate rially affect the structure of the iron. Chemical characteristics. Each of the chemicals added is controlled in amounts to produce the desired qualities in the castings. High carbon content produces soft iron; low car bon, hard iron. Silicon promotes graphitization, and high silicon content makes the iron softer. Manganese is added to minimize the detrimental effects of sulfur. Phosphorus makes molten iron easier to pour at low temperatures. In gray cast iron, the major part of the carbon content occurs as free carbon or graphite in the form of flakes inter spersed throughout the metal. An appreciable volume of graphite flakes makes gray cast iron more resistant to corro Steel pipe (lined and coated) being loaded. sion than the purer forms of iron because graphite does not corrode. When gray cast iron does corrode, the products of corrosion adhere tightly, protecting the metal underneath. Graphite in cast iron also affects the machinability of the pipe, that is, it makes the pipe more easily tapped and threaded for insertion of a corporation cock. Casting. The first cast iron pipe was molded in a horizon- tal position in short lengths of 3+ ft. Longer pipe lengths were produced by placing the mold at a slight angle, and the length was increased to 5, then to 9 ft, the standard for about 200 years. With the advent of pit casting in 1846, and the adoption of vertical molds, lengths were increased to 12, then 16 ft. Centrifugal casting. There are two centrifugal casting processes. The first, sometimes called the de Lavaud process after its inventor, quickly produces pipe from the molten iron. The casting machine consists essentially of a cylindri cal water-jacketed metal mold mounted on rollers so that it can be rotated at high speeds. The molten iron is fed into the mold from a small casting ladle containing the measured amount of molten metal required to make one length of pipe of the diameter and wall thickness desired. The mold is rotated at original speed until it has cooled to approximately 1500F. The pipe is then removed from the mold. The casting operation requires 1-1/2 to 8 min, de pending on pipe length and diameter. From the casting ma chine, the pipe passes through an annealing oven and is then ready to be coated and lined. Sand-lined mold. A second process for casting pipe cen- trifugally is the sand-lined mold process. Molds are pre pared by either of two methods. In one, a metal cylindrical flask is placed on end, and a metal pattern corresponding to the outside diameter of the pipe is centered within the flask. Molding sand is rammed into the annular space between the pattern and flask, then the pattern is withdrawn. In the other method, no pattern is used, and the mold is prepared by centrifugally lining the flask with a thermosetting, resinbonded sand mixture. The mold is placed horizontally on a centrifugal casting machine, on which it is spun by rollers, and prior to casting, the mold ends are closed with cores, one forming a bell socket. Molten metal is added in exact amounts, while the flask is spun, until the pipe has solidified; whereupon the casting machine is stopped and the flask removed. Gray iron cast in rammed sand molds is allowed to cool in the mold before removal and does not require annealing. Pipe cast in resin-sand molds is removed after solidification and oven-cooled under controlled time-temperature conditions. Ductile iron pipe. Ductile iron is defined as cast iron with graphite in spheroidal (nodular) form. It is produced by adding an inoculant, usually magnesium, to molten iron. Chemical characteristics. Ductile iron is chemically akin CTD000100 MAY 1967 | M 15 Handling cast iron pipe from railroad car to truck. Helicopter transports plastic pipe for service lines. to gray cast iron of low phosphorus and low sulfur content; the latter obtained by desulfurizing in the cupola. Magnesium can be added, after the removal of sulfur, in a post-inoculation treatment with a silicon-base magnesium alloy. These process steps produce a change in the manner by which the graphite is formed during the solidification of the iron. In gray iron, the carbon is interlaced in flake form in the iron. In ductile iron the graphite appears as myriads of isolated spheroids (Fig. 10). The matrix becomes rela tively continuous, and the strength, ductility, and impact re sistance of the metal are increased. Fig. 10. Microstructure of gray iron and ductile iron at same magnification. The mechanical properties of ductile iron are unlike those of gray iron. Ductile iron has a definite yield point, with a modulus of elasticity of 24 million psi. As a result of an extensive period of testing by manufac turers, it was determined that measurement of tensile and impact properties of test specimens cut from a pipe could define the basic quality of the ductile iron in the pipe. The minimum requirements were set at: ultimate strength, 60,000 psi; yield strength, 42,000 psi; elongation, 10 percent. Casting. Ductile-iron pipe is centrifugally cast in the same manner as gray cast iron, but the melting and inocula tion phase of the process is more complex; the casting phase is the same. A product specification for ductile iron pipe has been established (AWWA C 151), as follows:'8 Working pressure (psi) Nominal laying length (ft) Thickness tolerance (in.) 3-8 in. pipe 10-12 in. pipe 14-42 in. pipe 48 in. pipe Weight tolerance (%) 4-12 in. diam. 12 in. diam. and up Hydrostatic test (psi) Acceptance test (see "Testing") 350 18 and 20 0.05 0.06 0.07 0.08 Not less than 5 Not less than 4 500 Testing In selecting a product for a specific use, it is necessary to know how well the product will meet the requirements of the application to be met. For this reason, pipe production is controlled by specific tests. Gray cast iron pipe. Quality control tests in the modern pipe foundry include: frequent chemical analysis for each mix used in the cupola, chill tests for graphitizing tendency, Talbot strip tests, ring tests, bursting tests, and others. Several physical tests are utilized to make certain that the pipe will meet the following characteristics when installed: imperviousness, internal pressure capacity, tensile strength, toughness, beam-load capacity, and external load capacity. Hydrostatic test. Each length of pipe produced is sub- jected to a hydrostatic test at 500 psi, several times the normal working pressure. This test is made in a special ma chine that handles all sizes of pipe. Bursting test. A pipe's ability to withstand internal pres- sure can best be measured by submitting it to high hydrosta tic internal pressures. Periodic bursting tests in a special ma chine are run on full length specimens of pipe selected at random from any run of pipe production. Bursting pres sures, for 6-in. pipe, for example, are in excess of 2700 psi. Tensile strength. Termed the Talbot Strip Test, after the late Professor A. N. Talbot of the University of Illinois, the test for tensile strength consists of loading a 10-1/2-in. strip, cut from a pipe specimen, as a beam on supports 10 in. apart, with the load applied at the third points. These tests permit the manufacturer to certify the design value of the modulus of rupture of the iron. Deflection and beam load capacity. A pipe must be able to withstand beam stresses in handling and service. This characteristic is determined by a full length beam test, made on random selections of pipe at periodic intervals. Full length specimens are placed on supports 15 ft apart and subjected to load at the third points. Both the total load and deflection are recorded. Standard 6-in. pipe will usually deflect 2-1/2 in. and bear 21,000+ lb load before breaking. Ring compression test. To determine the ability of pipe to withstand external stress resulting from backfill and traffic loads, a ring compression or three-edge bearing test is used. A section of pipe, about 12 in. long, depending on pipe diameter, is cut from a pipe and tested as shown in Fig. 8. Load is applied at the top until the ring fails. In this test, a standard 6-in. pipe may be expected to carry a load of more than 19,000 lb per lin ft. The machine used determines both the deflection and the total load, which is applied at a stead ily increasing rate. From this test, the modulus of rupture is calculated; 40,000 psi is a minimum. Ductile cast iron. The acceptance tests applied to ductile cast iron pipe differ from those applied to gray iron. i M 16 | WATER AND WASTES ENGINEERING CTD000101 Hydrostatic test. Each pipe is subjected to hydrostatic tests of not less than 500 psi for at least 10 sec, either before or after the standard outside coating and bituminous inside coating have been applied. Tensile strength. The tensile test strip is cut longitudinally from the midsection of the pipe wall, and machined and tested according to ASTM designation E 8-61T. All tests are made at 70 10F. Minimum acceptable tensile strength is 60,000 psi. Impact test. Two impact tests are made at different temp eratures. The test is made in accordance with ASTM desig nation E-23-62, Notched Charpy Tests, except that the specimens are 0.500 in. wide and full thickness of the pipe wall. The impact values are adjusted to 0.4 in. At least one tensile and impact sample is taken during each casting per iod of 3 hr. Room temperature test. The adjusted acceptance value for tests conducted at 70 i: 10F is 7 ft-lb. ers. The hollow shaft is inserted to the far end of the pipe. The pipe is rotated rapidly while the mortar is extruded dur ing the withdrawal of the shaft. High speed rotation com pacts the mortar, removing excess water at the same time. The cement mortar after compaction is about 1/8-in. thick. It adheres closely, and the pipe may be cut or tapped without damage to the lining. Immediately following the lin ing process, the pipes are stored in a moist atmosphere for curing, or a bituminous seal coat may be applied to prevent too rapid loss of moisture. Pipe sizes Cast iron pipe comes in standard classes as to wall thick ness and in the following standard sizes: Gray cast iron (in.): Ductile iron (in.): 2, 3, 4, 6, 8, 10, 12, 14, 16, 18, 20, 24, 30, 36, 42, 48 4, 6, 8, 10, 12, 14, 16, 18, 20, 24, 30, 36, 42, 48, 54 Fig. 11. Types of cast iron pipe joints. Left to right: mechanical, bell and spigot, submarine. Low temperature test. These tests are made on at least one-third of the samples collected. The adjusted acceptance value for tests conducted at --40F is 3 ft-lb. Rejection. If a pipe specimen fails to meet any physical acceptance test requirement, all pipe cast in the same cast ing period is rejected, except as additional tests on other pipe sizes indicate acceptability. Coating and lining Although cast iron has a certain resistance to corrosion, there are some "aggressive" waters that cause the pipe to lose an appreciable part of its carrying capacity because of tuberculation. Tuberculation consists of the formation and growth of nodules of iron corrosion products within the pipe. Tar coating. The first attempt to control tuberculation and corrosion was the coaling of pipe inside and out with a bitumastic tar. Hot bitumastic tar is sprayed from applica tion nozzles to the inside and outside of each length of pipe and allowed to cool before storage. Tar-coated pipe resists tuberculation to a greater extent than uncoated pipe, but holidays in the coating allow penetration by the water, and some tuberculation results. Cement lining. The development in 1922 of a process for lining pipe with a thin coating of cement has made it possi ble to eliminate tuberculation and thus maintain the carry ing capacity of the pipe. The process of coating and lining pipe is the same for both gray cast iron and ductile iron pipe. The common method of cement lining is by the extrusion of cement mortar through a hollow shaft inserted into the pipe. The pipe to be lined is mounted horizontally on roll- Joints Pipe lengths may be joined together by several types of joints. Manufacturers can produce many types of joints. The following descriptions are given chronologically by de velopment. Illustrations of the various types of joints are shown in Fig. 11. The earliest type of joint was a tapered end inserted into a flared end of the pipe, probably with a tar seal of some sort. This idea later came to be the bell and spigot, but the original flare and taper joint lasted until the mid-1600s. Flange joints. The late 1600s saw the development of the flanged joint. The famous Versailles palace pipe line in stalled in 1664 utilized leather gaskets. Later gaskets were made of lead. This type of joint is still used for many above ground plant installations. Gaskets are usually of rubber, or rubber with cloth insertion. Bell and spigot. This joint was invented in 1785 and was used exclusively until the 1920s. It requires some means of sealing to make it watertight. Early installations used a vari ety of jointing materials, but calked lead soon became the preferred material; it is still in common use. Sulfur joint compounds were developed toward the end of the 19th cen tury and had a wide usage for many years, but are not pop ular now. Portland cement as a jointing material has been used to a limited extent (particularly in the Pacific Coast and Southwest states) for more than 50 years. Mechanical joint This type of joint was developed for the gas industry in the 1920s; it became popular with water utilities some time later. It utilizes the basic principle of the stuffing box and combines the fluid tightness of a flanged joint with a flexibility greater than that of the bell and spig ot joint. CTD000102 MAY 1967 | M 17 Fig. 12. Examples of slip joints for cast iron pipe joints. Submarine joint This joint is a type of ball and socket and is often so called. It can be deflected up to 15 degrees and is useful for installations across rivers. There is also a boltless type of flexible pipe joint employing the ball and socket principle. Push-on joint The most recently developed pipe joint is the most popular in water distribution systems today. The joint consists of a bell, with a specially designed recess to ac cept a rubber ring gasket, and a bevfcled-end spigot. The joint offers ease of installation, and when made up, the rub ber ring gasket is compressed to produce water tightness and is locked in place against further displacement. It is available in several designs (Fig. 12). Besides ease of in stallation and water tightness, the joint permits about 3 per cent deflection, a fact that makes it possible to install pipe on a curve. Shipping After manufacture, cast iron pipe is stacked in the yard to await shipment. All pipe receives a final inspection be fore shipping to make certain that it is in good condition. When shipped, the pipes are carefully lowered to the floor of the truck or railroad car. Special crane-operated hooks are used to prevent damage as the pipe is picked up. As loading proceeds, bell ends of pipe in alternate rows are stacked to face in opposite directions to guard against damage in transit. Packages of pipe separated by wooden blocking may be banded together by steel bands, for ease of handling and shipment. Damage from rough handling in transit is always a possi bility. Therefore, all pipe should be inspected when it is being unloaded. Rough treatment is usually evidenced by broken straps or wrecked wooden bracing that was placed at the foundry to minimize damage. Handling and unload ing of pipe is discussed in Part 3 on "Installation." Machine trenching operation. Section 3--Concrete Pipe Probably the earliest use of concrete as a water pipeline material was for a 12,336-ft. 38-in. concrete tunnel trans mission line installed on the Denver, Colo., supply in 1893. Concrete pipe as used today was fust installed in 1910 and came into wider use after 1930. The ingredients used in making concrete pipe are portland cement, sand and gravel aggregates, water, and rein forcing. Design There are three types of concrete water pipe, classified according to the method of reinforcement. These types are: steel cylinder, not prestressed; steel cylinder, prestressed; and non-cylinder, not prestressed. Table 14 sets forth the general design requirements and specifications for the three types of pipe. The material in this table was abstracted from AWWA Standard C 300-64,18 AWWA Standard C 30164,20 and AWWA Standard C 302-64.21 Steel cylinder type--not prestressed. Minimum thickness of wall and lining, and limitations on reinforcing are shown in Table 15, adapted from AWWA C 300-64.18 Minimum requirements for reinforcing are given in Table 14. Where the pipe is expected to be subjected to abnormal internal loads or water hammer, the reinforcing design must meet design requirements of the contract doouments. Steel cylinder type--prestressetL'Core thickness including the steel cylinder, and coating thickness are established ac cording to Table 16, excerpted from AWWA C 301-64.20 Design factors. Pipe may be designed for any normal combination of internal pressure and external load, but the minimum permissible combination is an internal design pressure of 40 psi and external earth load of at least 6 ft of earth cover, where the pipe bedding is ordinary. Unshored trench with 24-in. concrete pipe. TABLE 14--GENERAL DESIGN REQUIREMENTS FOR CONCRETE PIPE Material specifications included Pipe length (ft) Mortar coating (in.) Allowable tolerance from true rbund (in.) 36-in. diam. 42 to 48 in. 54 to 78 in. 84 in. up Min. wall and lining thickness, reinforcing, spacing, cages, etc. Core coating thickness specs. Steel cylinder Reinforcing Joint rings (steel) Rubber gaskets Steel cylinder, not orestressed; AWWAC 300-S4 Cement, fine and coarse aggre gate, water, steel (for cylinders, reinforcement, joints, rings, fittings, specials) 12, 14, 16 Steel cylinder, prestressed; AWWA C 301-44 Same as C 300-64, except fine ag gregate has requirements for both concrete, sand and mortar coating sand Min. 16 5/8 Noncylinder, not prestressed; AWWA C 302-44 Same as C 300-64 Min. 8 Max. 8-1/2 (12 to 15 in. diam.) 12 (16 to 21 in. diam.) 16 (24 in. diam. and up) 1/4 3/8 1/2 3/4 See Table 15 1/4 3/8 1/2 3/4 1/4 3/8 1/2 3/8 See Table 17 See Table 16 Welded steel, not less than 10 gage Same as C 300-64 Cajge and cylinder cross section limited to area producing max. stress of 12,500 psi under de sign operating conditions; area of cage must be a min. of 40% of combined area of cage and cylinder Wire for circumferential reinforce Rods or bars--ASTM ment must meet ASTM Des.A 227 Des. A 15 structural for hand drawn spring steel wire grade Min. 8 gage Wire: ASTM Des. A 82 Wire fabric; ASTM Des. Gross wrapping stress less than A185 75% of wires ultimate min. ten sile strength Min. space between wires, 3/16 in., max. 1-1/2 in. Self-centering Same Same Specified composition to meet specifications for tensile strength, elongation at rupture; specific gravity, and cold flow; must completely fill recess TABLE 15-DESIGN REQUIREMENTS FOR REINFORCED CONCRETE PIPE--NOT PRESTRESSED* Pipe wall Pip* ID fin.) Min. thickness (In.) Allowable variation b*low normal (In.) Concrete lining min. thickness (In.) Reinforcing spacing Min. (In.) Max. (In.) 20 24-30 36 42 48 54 60 66 72 3-1/4 3-1/2 4 4-1/2 5 5-1/2 6 6-1/2 7 1/8 1/8 1/8 3/16 3/16 1/4 1/4 1/4 1/4 1 1 1 1 1-1/4 1-1/4 1-1/4 1-1/2 1-1/2 1-1/4 1-1/4 1-1/4 1-3/4 1-3/4 1-3/4 1-3/4 2 2 4 4 4 5 5 5 5 6 6 * Pipe from 78 to 96 in. also has specified minimums not included in Table 1, and pipe larger than 96*in. must meet specifications of purchaser. Pipe design must also consider transient conditions caused by short-duration overloads resulting from water hammer or e-tternal live loads (traffic). The final design may not exceed the design limits for either of these two con ditions: (1) normal operating pressure plus water hammer plus backfill load, or (2) normal operating pressure plus backfill plus live traffic load plus impact. Design procedures. Either of two procedures may be used for the calculation of the core thickness of the pipe and the wire area, tension, and spacing under which the wire is wound. The Appendix A procedure of AWWA C 300-6419 is generally used east of the Rocky Mountains, and the Appendix B procedure is used west of the Rocky Mountains. The first combination design procedure utilizes the cubic parabola method20 to determine the combination of design pressure and earth load. The design curve is expressed by this equation: W._ \/Po - pj Eq. 10 where w = maximum three-edge bearing load, equivalent to earth load in combination with design pres sure p (psi) Wo = 0.9 multiplied by the three-edge bearing load that produces incipient core cracking with no internal pressure (lb per lin ft)* P0 = internal pressure require to overcome all com pression in the core concrete, exclusive of ex ternal load (psi) p = maximum design pressure in combination with the three-edge bearing load (w), it may not exceed 0.8 P0 for lined cylinder pipe (psi) Three-edge bearing loads are based on manufacturers' lest data. CTD000104 MAY 1967 | M 19 Po M Po INTERNAL PRESSURE Fig. 13. Cubic parabola design curves for concrete pipe.1* Graph (a) is for lined and Graph (b) embedded cylinder pipe. In both graphs, T designates the transient-load curve and D the design curve; w, is for the three-edge-bearing load equiva lent to live load; and Pwh Is for water hammer in excess of the normal operating or design pressure. The design resulting from the calculation is varied to make the specific combination of internal pressure and earth load fall on or under the curves (a and b) published in AWWA C 301-64" (see Fig. 13). According to Appen dix A of AWWA C 301-64, "the resulting design has a tran sient load capacity equal to the difference between the de sign pressure or earth load and the value determined from the extension of the appropriate line for water hammer or live load until it intersects the transient-load curve." (See AWWA C 301-64" for details.) Where water hammer exceeds 40 percent of design pres sure, or live load (including impact) exceeds the AASHO H20* loading, the greater value should be used. American Association of State Highway Officials. The second combination design procedure utilizes the stress analysis method. In this method a different equation and a different set of curves are used. The calculation, how ever, results in a design with "a transient-load capacity equal to the difference between the design pressure or earth load and the value determined from the extension of the appropriate line [in the published curves20] or live load until it intersects the transient-load curve." (See AWWA C 301-64" for details.) If water hammer or earth load exceeds stated values, the design should reflect the conditions to be expected. Noncylinder type--not prestressed. Minimum and nomi nal requirements for pipe wall thickness and reinforcing re quirements are shown in Table 17, extracted from AWWA C 302-64.21 When earth cover is nominal, the pipe is de signed for internal pressure with a steel stress of 12,500 psi. According to AWWA C 302-64,21 where external loading is the determining design factor, a combination analysis must be made to determine the steel area. For combined load designs, tensile stresses in the tension steel should not ex ceed 22,000 psi, and compressive stresses in the concrete should not exceed 45 percent of the specified 28-day strength. Manufacture The manufacture of concrete pipe begins with fabrication of the steel cylinder and/or steel reinforcement cage, a process that is done in accordance with the AWWA Standards.le'"-21 Table 18 is a brief presentation of the items included in the manufacturing process requirements as set forth in the AWWA Standards.18-20 21 Testing and rejection. There are specifications for limits on various characteristics of materials used in the manu facture of concrete pipe. Most of these characteristics are in cluded in Table 18. For the most part, the specified testing procedures are those set up by pertinent ASTM designa tions. Hydrostatic pressure tests and external loading tests on finished pipe are made only when specified by the pur chaser. Hydrostatic tests of cylinders are made as stated below.21 i Hydrostatic tests. This test may be made on individual randomly selected lengths or on two lengths joined together. Watertight bulkheads are used to close the pipe ends. The pipe is filled with water to the design pressure. (This type of pipe is allowed to stand two weeks.) The pressure is then increased gradually to 120 percent of design pressure and checked at the end of 20 min. Evidence of cracks, leakage, or leaking joints is cause for rejection. On noncylinder pipe, damp spots on the surface are not. TABLE 18--DESIGN REQUIREMENTS FOR REINFORCED STEEL CYLINDER CONCRETE PIPE--PRESTRESSED81* P|B* (In.) 16 18 20 24 30 36 42 48 54 60 66 72 Pipe with lined cylinder Core thickness (In.) Maximum design pressure (in.) 1 1-1/8 1-1/4 1-1/2 1-7/8 2-1/4 2-5/8 3 250 250 250 200 200 200 175 150 Pipe with embedded cylinder Core thickness (In.) Maximum design pressure (psi) 2-1/4 2-1/4 2-1/4 2-5/8 3 4 4-1/2 5 5-1/4 275 240 210 190 175 200 200 200 200 Coating thickness Mortar (min. thickness over the wire) (In.) Concrete (nominal thickness over the core) (in.) 5/8 1-1/2 5/8 1-1/2 5/8 1-1/2 5/8 1-1/2 5/8 1-1/2 5/8 1-1/2 5/8 1-1/2 5/8 1-1/2 5/8 1-1/2 5/8 1-1/2 5/8 1-1/2 5/8 1-1/2 * Pipe from 78 to 96 in. also has specified minlmums not included in table, and pipe over 96-in. diameter with embedded cylinder must meet de sign specifications of the purchaser. M 20 | WATER AND WASTES ENGINEERING CTD000105 TABLE 17--DESIGN REQUIREMENTS FOR NONCYLINDER CONCRETE PIPE--NOT PRESTRESSED* Pipe ID On) 6000 psi centrifugal concrete Min. pipe wall thickness On) Min. no. of cages 4900 psi pound concrete ------------------------------- ---------------- Nominal pipe wall thickness Min. no. On) of cages Circumferential reinforcement spacing .. - - Min. Max. On.) On.) Min. total steel area (*q In.) 12 2 i 1-1/4 4 0.08 15 2 i 1-1/4 4 0.11 16 2-1/8 i 1-1/4 4 0.12 18 2-1/4 i 1-1/4 4 0.14 20 2-3/8 i 1-1/4 4 0.16 21 2-3/8 i 1-1/4 4 0.17 24 2-1/2 i3 i 1-1/4 4 0.20 27 2-5/8 i 3-1/4 i 1-1/4 4 0.23 30 2-3/4 i 3-1/2 i 1-1/4 4 0.25 33 2-7/8 i 3-3/4 2 1-1/4 4 0.28 36 3 i4 2 1-1/4 4 0.30 42 3-1/2 2 4-1/2 2 1-3/4 5 0.35 48 4 25 2 1-3/4 5 0.40 54 4-1/2 2 5-1/2 2 1-3/4 5 0.45 60 5 26 2 1-3/4 5 0.50 66 5-1/2 2 6-1/2 2 2-1/4 6 0.61 72 6 27 2 2-1/4 6 0.71 * For pipe larger than 96 in. in diameter, dimensions and details of design shall be subject to approval by the purchaser. TABLE 18--MANUFACTURING PROCESS SPECIFICATIONS FOR CONCRETE PIPE Steel cylinder--not prastrassed AWWAC J0&64 Steel cylinder--prestressed AWWA C 301-64 Noncylinder-- not stressed AWWA C 302-64 Cylinder fabrication Shape to size; lap weld Shape to size; butt weld Reinforcement Continuous or welded steel rod or wire, butt welded, (tested to stress specifications); helically wound Continuous steel rod, applied around core, at designed predetermined spacing and tension, 7 days after pouring Same as C 300-64 Hydrotest Test to 20,000 to 26,000 psi stress Concrete Proportioning ingredients Material measurement Mixing Cylinder test Control to obtain homogeneous, dense, workable, durable concrete of specified strength Measure cement, aggregate, and water within 1% accuracy Use approved mixing time consistent with mixer used Follow ASTM Des. C-31 Compressive strength Standard 7 day (psi) 3000 3000 3000 28 day (psi) 4500 4500 4500 Centrifugal cast 7 day (psi) 28 day (psi) 4000 4000 7000 6000 Forms Use smooth welded, steel, nonleaking forms, cleaned and oiled between each pour Placement Use approved methods only. Do not remove forms until concrete sets Core may be centrifugally or vertically cast under specified procedures Pipe coating Use mortar or concrete of approved mixture, and cure Interior seal coat Add bituminous coating if purchaser so specifies Hydrostatic tests on cylinder-type pipe are made on the cylinder, with joint rings welded to its ends, at a steel stress between 20,000 and 25,000 psi. External load crushing tests. These tests are made in ac cordance with ASTM dsignation C 497 and are generally limited to the loading required to produce the first crack 1 ft long. The purchaser sets the conditions of loading and acceptance. Coating on lining. If the purchaser so specifies, concrete pipe may be coated inside with a cutback asphalt, spray applied. This coating is normally required only for waters having a negative Langlier index. Pipe sizes. The AWWA Standards list specifications up to 96 in. diameter, but concrete pipe can be made in any size and has been produced in diameters up to 180 in. Joints. Jointing for concrete pipe employs a modified bell and spigot arrangement, in which a gasket is used to ensure a tight fit (see Table 14), and the space between pipe lengths is filled with mortar. Pointing is used for the interior joint recess, and the outer joint is filled by placing a cloth diaper around the adjoining pipe ends as a form to pour the mortar. Shipping. Concrete pipe may be manufactured at the site or at a central plant. It may be shipped by rail or truck; in either case it should be protected against damage enroute. CTD0001C6 MAY 1967 | M 21 Section 4--Plastic and Plastic-Lined Pipe Plastic pipe as a commercial product was first introduced in Germany in 1930 and in this country in 1940. Polyvinyl chloride (PVC) was the first type produced. Later came cellulose acetate butyrate (CAB) and polyvinyledine chlo ride (Saran). Volume production of plastic pipe began in 1948, when polyethylene (PE) was accepted for various water uses. Early development of pipe for water use was accompanied by studies to determine that the materials were nontoxic when used in water supplies. The outgrowth of these studies was a testing and approval program by the National Sanita tion Foundation. All pipe offered for use in the water sup ply industry now carries an NSF seal of approval. Early production of plastic pipe was in sizes under 2 in., and most of the plastic pipe sold was for service lines and household plumbing systems. As developments in the plas tics industry progressed, larger pipe sizes became available, and plastic pipe is now being used for water distribution mains in many localities in this country, as well as for serv ice and inplant piping systems. With reference to acceptance, the Plastics Pipe Institute reports that more than 50,000 miles of plastic piping was in stalled in potable water systems in 1965, mostly outside buildings. It is also reported that since 1953 the Farmers Home Administration has approved plastic piping for rural water systems, and that from 1960 to 1965, FHA financed more than 10,000 miles of water distribution pipe, most of it plastics. Design There are two major types of plastic material: thermo plastic resins and thermosetting resins. Thermoplastic mate rials can be softened and reshaped repeatedly by the appli cation of heat. Thermosetting materials set or harden per manently after a single heating. The former are generally lower in. strength and have inferior resistance to deteriora tion by heat, but they are easier to fabricate. Thermosetting resins and the following thermoplastic resins are not used in water systems: acrylics (ethylmethacrylate, Lucite, Plexi- Lowering cast iron pipe into trench with a clamp. glas), high impact styrene, and Lexan (aromatic polycar bonates). All plastic pipe used in water supply systerris is manufac tured in accordance with ASTM, Department of Commerce Commercial Standards, and USASI Standards. A number of manufacturers produce pipe of higher quality characteris tics than specified by the commercial standards. Table 19 contains an alphabetical listing of various plas tic materials that are, have been, or may be used in water systems. Only three are in common use today, PVC, PE, and ABS, in that order; ABS is now used primarily for drainage, waste, and vent (DWV) fittings and pipe for inte rior application. ABS was popular a few years ago for water systems, but inasmuch as it has only half the available hoop stress, compared to PVC, wheil subjected to internal pres sure, the latter product is considered to be a better material for water lines. Nam* ABS Composition Polymers of acrylonitrile, butadiene, styrene CAB Cellulose acetate butyrate Delrin Linear acetal Penton Chlorinated polyether PE Polyethylene PVC Polyvinyl chloride PP Polypropylene Saran Vinylidene chloride Teflon Fluorocarbons TABLE --FUSTIC PIPING MATERIALS Application Standard No, Inplant chemical lines; service lines ASTM D2282-65 CS 254-63 USASI B72.3-67 Salt water; water lines; inplant systems Water lines Pipe lining Distribution mains; service lines; inplant systems Distribution mains; service lines; inplant systems Service lines; Inplant systems ASTM D2239-65 CS 256-63 USASI B72.1-67 ASTM D2241-65 CS 255-63 USASI B72.2-67 Pipe lining Pipe lining; inplant systems Comment Chemically resistant; lightweight; can bethreaded, solvent welded, or slip coupled; low mechanical strength Range from flexible to rigid; can be threaded, slip sleeved, or sol vent welded; low heat resistance Good mechanical properties; sta bility; low heat resistance Good heat resistance; dimensional stability; chemical Inertness Resists impact at subzero tem peratures; flexible, noncorrosive, soft Some forms resist impact; can be cut, threaded, welded, drilled; non combustible; rigid Greater high temperature resist ance than PE; poor resistance to low temperature Chemically resistant; brittle at low temperature Self-supporting tubing M 22 | WATER AND WASTES ENGINEERING CTD000107 For the purpose of this manual, this section will be limit ed to ABC, PE, PVC, and plastic lined pipe. Characteristics. All plastic pipe has an exceptionally smooth interior surface and a C-value of at least 150, thus minimizing loss of head in lines. All these materials are chemically inert, corrosion resistant, and do not react in any way with the water that passes through the pipe. Pressure rating. All plastic pipe manufactured under the standards listed in Table 19 is made in standard thermo plastic pipe dimensions and is pressure rated for water at 160 psi or above. Plastic pipe is pressure-rated at a standard temperature of 73.4 F, and pressure resistance decreases with temperature until a critical point is reached above 150 to 160 F. Table 20 shows this temperature-pressure relationship. Tempera ture for pipe in buried applications is not critical because most water temperatures run below 73.4 F. The only criti cal time for temperature considerations is during installa tion periods. The standard thermoplastic pipe dimension ratio (SDR) is the ratio of pipe diameter to wall thickness. In the case of ABS and PVC pipe, the outside pipe diameter is used; for PE, the inside pipe diameter is used. Pressure rating (PR) is the estimated maximum operat ing internal water pressure (psi) at which the pipe can function without failure. The relation between SDR, hydrostatic design stress, and pressure rating is given by either Eq. 11 or Bq. 12. These equations are commonly known as the ISO equations. For ABS and PVC pipe: 2 S cri_ , 2 S OD ~f = SDR - 1 or y = -- - 1 Eq. 11 For PE pipe: ^ = SDR + lory + 1 Eq. 12 where, for the two equations S = hydrostatic design stress (psi) P = pressure rating (psi) OD = outside diameter (in.) ID = inside diameter (in.) t = minimum wall thickness (in.) SDR = standard thermoplastic pipe dimension ratio, i.e., (OD/t for ABS and PVC; and ID/t for PE pipe). Manufacture AH thermoplastic pipe is manufactured by an extrusion process; fittings by an injection mold process. In the extru sion process, pellets of plastic material are heated under pressure and forced through a shaping die, such that they conform to the dimensional requirements of the piping product. Subsequent to this shaping process, the product is TABLE II--PLASTIC PIPE PRESSURE RATING VS. TEMPERATURE Tamp (* F) 60 73.4 100 130 Rating In terms of 73.4'F (%) ABS PE PVC 105 110 115 100 100 100 84 70 60 67 30 slowly cooled and further shaped through sizing devices to make its dimensions fall within that required by standards. Material. The standards under which plastic pipes (ABS, PE, and PVC) are manufactured specify that the plastics used to make pipe are categorized by two criteria: short term tests and long-term tests. TABLE II--MATERIAL REQUIREMENTS AND PIPE CLASSIFICATION FOR ABS, PE, AND PVC PIPE Pips das. Material Hydrostatic Prossura rating (psi) ------------------------ design stress --------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Type Grade (psi)* SDR 7 SDR S SDR 11.5 SDR 13.5 SDR IS SDR 17 SDR 21 SDR 26 SDR 32.5 SDR 41 SDR 64 ABS 1106 I ABS 1210 I ABS 2112 II 1 2 1 630 1000 1250 ACRYLONITRILE-BUTADIENE-STYRENE (ABS)** 100 80 160 125 200 160 100 125 80 100 PE 2305 PE 2306 PE 3206 PE 3306 II II III III POLYETHYLENE (PE)t 500 125 100 80 630 125 100 630 125 100 630 125 100 80 80 80 PVC 1120 PVC 1220 PVC 2110 PVC 4116 I I II IV 1 2 1 1 2000 2000 1000 1600 POLYVINYL CHLORIDE (PVC)tt 315 250 200 160 125 100 63 315 250 200 160 125 100 63 160 125 100 80 63 50 250 200 160 125 100 80 50 * At 23*C (?3.4*F). ASTM bes. D1788-60T. t ASTM Das. D1243-60T. Tt ASTM Das. D1764-60T. CTD000108 MAY 1967 | M 23 Most plastic pipe is manufactured from virgin material, but the standards* allow the use of rework material (only within the same production plant) as long as the pipe produced is of equal quality to that extruded from virgin material. The raw materials used in the manufacture of thermo plastic pipe and fittings are products of petrochemical tech nology and basically consist of extremely long hydrocarbon molecules. By combining various ingredients, an unlimited range of materials and physical properties can be generated. The thermoplastic materials commonly used in water serv ice and distribution lines are selected for this application. They are based on a favorable combination of physical and economic properties to ensure a system of long life at low initial and maintenance costs. Table 21 gives the material requirements, pipe classifica tions, and pressure ratings for ABS, PE, and PVC plastic pipe. Tolerances. Plastic pipe diameters and wall thicknesses are held to close tolerances throughout the range of sizes, types of material, and standard dimension ratios. The limi tations of these acceptable tolerances are shown in Table 22. Within these minimum to maximum ranges are other ranges that relate to different standard dimension ratios for the different pipe materials. A tolerance of 1 in. is allowed in pipe lengths of ABS and PVC pipe. mensions, it conforms to IPS dimensions. As a result, the outside diameter of polyethylene pipe "floats" and cannot be associated with any other sizing system. The reason for the ID control on polyethylene pipe was that joining of these materials was first accomplished through ID fittings rather than OD connection commonly found in ABS or PVC. Plastic pipe for water supply system use is available in a wide range of sizes, as follows: ABS: 1/2, 3/4, 1, 1-1/4, 1-1/2, 2, 2-1/2, 3, 3-1/2, 4, 5, 6, 8, 10, 12 PE: 1/2, 3/4, 1, 1-1/4, 1-1/2, 2, 2-1/2, 3, 4, 6, PVC: 1/2, 3/4, 1, 1-1/4, 1-1/2, 2, 2-1/2, 3, 3-1/2, 4, 5, 6, 8, 10, 12, 16 There are smaller sizes available, but these are not used for house service lines. There are also some exceptions to the above listing in some of the SDR categories, particularly in ABS and PVC pipe. ABS and PVC, being semi-rigid products, are normally supplied in 20- to 39-ft lengths. PE pipe, being flexible, is supplied in coils 100 to 500 ft in length. The straight lengths are shipped in bundles containing 100 ft, normally unpro tected. Premium (ultra-high molecular weight PE) is sup plied wrapped or in cartons for on-the-job dispensing of the desired amount for the service line being installed. TABLE 21--MANUFACTURING TOLERANCE RANGES FOR FUSTIC FIFE Measurement Out-of round ness (in.) Wall thickness Tolerance (in.) 10 (in.) Tolerance (in.) OD (in.) Tolerance (in.) ABS Min. Max. PE Min. Max. PVC Min. Max. 0.008 0.075 0.10 0.606 0.06 0.404 0.06 0.75 0.020 0.073 0.020 0.048 +0.02 +0.09 0.622 6.065 -0.035 +0.020 0.405 12.75 0.008 +0.075 Pipe sizes There are three different sizing systems commonly used on plastic pipe. The IPS (iron pipe size) was the initial dimensioning system adopted by the plastics pipe industry. It is still in use today. Recognition of the strength properties of plastics brought about a new sizing system, termed the SDR-PR (standard dimension ratio-pressure rated) system. The system differs from the IPS system in that pipe of any size made to the SDR basis has the same pressure rating. That is, the user can purchase ABS or PVC, for instance, with a 160-psi pressure rating in all sizes ranging from Vi to 6 in. Using the IPS system, this is not possible because of the decrease in pressure rating with increasing size, i.e., there is not a cons:. nt relationship between OD and wall thickness. The third pipe sizing system, commonly termed the SWP (solvent weld pipe) system, is associated with ABS material exclusively. This system has almost completely given way to the SDR system because it was extremely difficult to use SWP pipe and then adapt the more common IPS system. Although the SWP system is still in existence, it is now used generally for only submersible and jet pump installation rather than for service line or water distribution pipe. It should also be pointed out that the SDR system is based on IPS ODs so that it is completely compatible with the IPS system. SWP pipe is not compatible with either SDR or IPS. Polyethylene pipe is based on the SDR system as well, but instead of the OD conforming to IPS system di- Testing Plastic pipe is subjected to the following tests during manufacture: Test ABS PE PVC Carbon black V Ballooning VV V Bursting pressure VV V Density V Eccentricity vV V Environmental cracking V Extrusion quality V V Failure VVV Rattening V ID measure V OD measure V V Seepage or weeping V V V Sustained pressure V V V Wall thickness VV V All tests are conducted under rigid controls at the stand ard test temperature of 23C (73.4F). The test conditions set for pressure tests vary not only with the composition of the pipe, but also with the standard dimension ratio categories. The tabulation of data in Table 23 indicates the ranges of pressures used. The data also in- Lowering 66-in. steel pipe into trench with a sling. * See Table 19 for standard designation. M 24 | WATER AND WASTES ENGINEERING CTD000109 TABLE 2}--DATA ON PRESSURE TEST RANGES FOR FUSTIC PIPE SDR 5 SDR 7 SDRS SDR 11 SDR 13.5 SDR 15 SDR41 SDR W Pipe des. Sust. press.* (psl) Burst. Sust. Burst. Sust. Burst. Sust. Burst. press.** press. press. press. press. press. press. (psi) (psi) (psi) (psi) (psi) (psi) (psi) Sust. press. (Psi) Burst. Sust. Burst. Sust. Burst. Sust. Burst. press. press. press. press. press. press. press. (psi) (psi) (psi) (psi) (psi) (psi) (psi) ACRYLONITRILE-BUTADIENE-STYRENE (ABS) ABS 1106 680 ABS 1210 1070 ABS 2112 1350 1650 2620 3300 340 830 270 660 220 530 540 1320 430 1050 340 830 680 1650 540 1320 430 1050 70 160 110 240 140 330 PE 2305 PE 2306 PE 3206 PE 3306 POLYETHYLENE (PE) 265 500 210 400 170 320 265 500 210 400 265 500 210 400 265 500 210 400 165 320 165 320 165 320 PVC 1120 PVC 1220 PVC 2110 PVC 4116 2100 2100 1150 1840 3170 3170 2500 3170 1050 1050 580 920 POLYVINYL CHLORIDE (PVC) 1600 840 1250 1600 840 1250 1250 460 1000 1600 740 1250 670 670 370 580 1000 1000 800 1000 210 320 130 210 320 130 120 250 70 180 320 120 200 200 160 200 * Sustained pressure--1000 hr. ** Bursting pressure--60 to 90 sec. dicate that as the SDR increases, that is, as the pipe diame ter increases with respect to wall thickness, the maximum sustained pressure and bursting pressure levels decrease. Joints There are several types of jointing methods and systems used for plastic pipe, and these methods vary with the type of material. ABSpipe. This type of pipe is available with fittings of all types, and connecting joints may be made by screw-thread ed couplings, solvent weld, or with victaulic or Dresser-type joints. Inasmuch as this type of material is not used for water service systems as frequently as the other materials, the subject of joints is of less interest. PE pipe. There are basically two methods of joining poly ethylene: insert fittings and flaring. One of the reasons that PE pipe sizing is based on inside rather than outside diame ters is that the joining of these materials was first done by means of inside fittings. As a result, joining had to be ac complished by mechanical means, such as insert fittings etc. The polyethylene material, because of its inherent low mod ulus, high flexibility, cold flow, or creep characteristics, could not be permanently joined through an outside clamp ing or mechanical joining device without an internal sup port. The initial joining system thus became associated with internal support and is commonly known as the insert fit ting method. Recent developments with polyethylene have made the material capable of being flared in a manner similar to cop per and joined directly into conventional curb and corpora tion stops. Flaring is normally accomplished by specially de signed flaring tools and the application of heat to the end of the pipe so that the material can be softened and flared easi ly. As a result, a new sizing system, the tubing-size system, has developed for polyethylene. In this system, the OD of polyethylene is exactly the same as ODs for Type K copper tube. The inside diameter thus floats and is dependent on pressure rating. This tubing is joined by flaring rather than by insert fittings. A third system for joining PE pipe is also evolving. It is termed the compression joint method and can be accom plished on copper-tube-sized pipe as well as IPS-ID pipe. In this system, the use of internal metal stiffener sleeves is nor mally recommended. The pipe is joined by means of a com pression fit between an O-ring around the circumference of the pipe. The O-ring is pressed against the pipe surface and resisted principally by the internal support sleeve. The use of polyethylene for water service applications has witnessed the use of all three joining methods, although the insert fit ting methods is the most common and oldest system in use. Flaring requires a little more skill in installation than does the use of insert fittings. The compression joint system is probably the easiest to install. PVC pipe. There are several means of joining PVC pipe sections. In the solvent-weld system, the pipe and fitting are chemically joined through the use of solvents that degrade the outer surface of the material. Basically this action plasti cizes the plastic such that when pipe is mated to the fitting, the solvated plastics on the fitting and pipe side are mixed. The solvent evaporates leaving a monolithic joint. In addition, belled-end PVC is available in two fashions, one a straight bell on one end of the pipe, which basically eliminates a coupling. It employs the solvent weld system. The other method is an O-ring joint employing a belled end in which an O-ring is fitted (Fig. 14). This system is devoid of solvent-weld-type of joining; sealing is accomplished Fig. 14. PVC pipe joint for large size pipe. MAY 1967 | M 25 completely hy compression of the O-ring against the pipe. The O-ring system is associated with the larger PVC water distribution applications because of the relative ease of join ing and the speed to which it can be accomplished com pared to solvent welding. For PVC, other joining methods can be employed, such as the victaulic method, flanged fitting, etc., but the meth ods listed above are the most common, most economical, and easiest to use. Plastic-lined pipe There are at least three plastic materials used to line cast iron and steel pipe. These lining materials are Penton (chlo rinated polyether), polypropylene, and Saran (vinylidene chloride). All three are chemical- and corrosion-resistant. Design. Plastic pipe liners are nearly hydraulically smooth. When it is necessary to estimate the pressure drop in any plastic-lined pipe line, the following equation is used: D 0.0D2*86i/pG)y-" ,,^ ,13, where P = pressure loss in line (psi/100 ft) G = flow (gpm) D = inside pipe diameter (in.) Manufacture and testing. Manufacture of plastic-lined steel pipe involves locking the stabilized plastic liner firmly inside the pipe so that the liner and tube expand and con tract as one unit. The outside diameter of the plastic-lined steel pipe is made to stadard iron pipe sizes. During the lining process, the lined pipe is spark-tested twice to ensure product quality. The pipe is designed for ei ther 125 or 150 psi pressure classes.- Pipe sizes, lengths, and joints. Plastic-lined pipe is manu factured in these sizes; I, 1-1/4, 1-1/2, 2, 2-1/2, 3, 4, 6, and 8-in. diameters, and in 10-ft lengths. Joints are made by flanged fittings screwed on to threaded pipe ends. The pipe may be cut in the field and threaded for use with couplings or flange connections. The pipe ends are protected against damage during shipment. Section 5--Steel Pipe Steel pipe in water systems dates back more than 100 years. Its early use for carrying water was in large, long, and exposed transmission lines in relatively dry areas where corrosion was not a problem. Other applications in other areas became more common as coal-tar coatings became available. Steel pipe is now used in many distribution and inplant systems, as well as in transmission lines. Steel pipe has four characteristics that make it useful in water systems: strength, an ability to resist load but yield to it, an ability to bend without breaking, and resistance to shock. A full treatise (AWWA Ml l)22 on steel pipe, its charac teristics, uses, standards, design, manufacture, and installa tion has been published by the American Water Works As sociation, which has also published a number of standards related to steel pipe.23-24-26-27 Design As described by AWWA Standards,23-24 there are two types of steel water pipe*: fabricated, electrically-welded steel pipe and mill-type steel pipe; both may be coated and lined. In determining the required Wall thickness of either type, the designer must consider all factors that affect design. These factors are: internal pressure (static and surge), external load (trench load, earth fill, and uniform collapse pressure, either atmospheric or hydraulic), special physical loading (for saddle or ring supports), and practical requirements. All of these factors are discussed in detail in AWWA Manual Mil.22 Once the internal pressure conditions are established, the wall thickness is calculated according to this equation where t = wall thickness (in.) p = pressure (psi) d = outside diameter (in.) s = allowable stress (psi)* * Normally SO percent of yield strength of steel selected. Tables are available22 for selecting wall thickness directly, based on Eq. 14. The following discussion of pipe design is divided be tween the two types of steel pipe and is based on AWWA standards.23,24 _ Fabricated, electrically-welded pipe. AWWA Standard C201-6623 gives a description of the pipe with respect to material, pipe dimensions, ends, and seams. Steel plate. Plate used for fabrication must be Grade B, C, or D of ASTM Des. A 283 "for low and intermediate tensile strength for structural quality." When requested by the purchaser, specimen plates for testing must be submitted by the manufacturer. When large diameter steel pipe is used, the wall thickness is often governed by internal pressure, but external load and deflection control may dictate the required wall thick ness. If high water pressures exist, a steel plate of higher strength than the above grade should be used for the pipe. Steel sheets and coils. Sheet or coil steel must be Grade A of ASTM Des. A 245 "for light-gage, structural-quality, flat, hot-rolled carbon steel." Test results certifying physical properties of the steel pipe must be furnished. Plate thickness. In the determination of required steel * These standards relate to the original methods used to produce steel pipe. Now, there is essentially no difference, and a committee has been established to merge the two standards into one. M 26 | WATER AND WASTES ENGINEERING CTD000111 pipe plate thickness, Eq. 14 is adapted to include the factor of joint efficiency as follows: pR t= fte Eq. 15 where t = pipe thickness (in.) p = internal bursting pressure (psi) R = pipe radius (in.) ft = allowable unit stress (psi) e = joint efficiency Welded pipe is considered to have a joint efficiency of 1.0, but for riveted pipe the value of e is taken as the smal ler of the two calculated values: plate efficiency and rivet efficiency. With the modern welding techniques available, rivet pipe is rarely used anymore and may be considered obsolete. The design of plate-steel pipe must also take into consid eration combined direct and flexural stresses caused by ex ternal loads, temperature, jointing, and support arrange ments, etc. To prevent buckling as a result of critical external pres sures, stiffening rings may be used. The critical pressure without stiffening rings is given by Equation 16. (Note: these critical pressures refer to uniform pressure exerted on a pipe aboveground or in a subaqueous installation.) 5E(t)' 3d Eq. 16 where P = external pressure (lb per lin ft) E = modulus of elasticity of metal (psi) t = pipe wall thickness (in.) d = pipe diameter (in.) Tolerances. Manufacturing tolerances23 are set for end, size, length, straightness, and bead. Ends. For a distance of 10 in. from the ends, both outside and inside diameters for different types of joints must be within these limits: not more than 1/16 in. smaller or more than 1/8 in. larger than the nominal circumference calculat ed either from the nominal outside diameter or the nominal inside diameter plus twice the nominal wall thickness. Slip joint bells and tapered sections for lap riveted field joints have these tolerances: inside diameter of bell--plain end diameter + 1/32 to 3/16 in. Tapered sections diameter--inside section diameter + 1/16 to 1/8 in. Size, length, straightness, and bead. Tolerances for these physical measurements of steel pipe are as shown in Table 24. In bell and spigot rubber gasket joint pipe, the tolerance Lowering asbestos-cement pipe into trench with a clamp. Underwater pipeline installation. difference between inside diameter of the bell and outside diameter of the spigot is 0.06 in. minimum and 0.2 in. maximum. TABLE 14--MEASUREMENT TOLERANCES FOR ELECTRICALLY-WELDED STEEL PIPE Measurement Tolerance Outside circumference (%) <20 in. diam. >20 in. diam. Straightness deviation (in.) 10-ft length Length (in.) Pipe sections Special straight sections Weld bead height* Outside, max. (in.) Inside, max. (in.) 1.0 0.5 1/8 2 1/8 +1/8 +1/16 * Bead may not be below surface at any point. Mill-type steel pipe. AWWA Standard C202-64T24 sets forth specifications for chemical and mechanical prop erties for three mill types of pipe, as follows: Type Grade Weld type Furnace welded Electrically welded Seamless Continuous furnace weld or furnace butt weld A, B, or X 42 Induction butt weld; spiral- or straight-seam resistance butt weld; spiral- or straight-seam fusion butt weld A, B, or X 42 Chemical properties. Steel supplied for use in pipe should conform to a ladle analysis as shown in Table 25. Mechanical properties. The minimum required tensile strength of the steel will vary depending on the grade used, as shown in Table 26. TABLE IS--MAXIMUM ALLOWABLE CHEMICAL CONTENT OF STEEL Steal type Furnace butt-welded Grade A Grade B Grade X 42 Manganese 0.65 1.25 1.25 1.25 Phosphorus <%> 0.11 0.04 0.11 0.10 Sulfur (%) 0.06 0.05 0.05 0.05 TABLE IS--MINIMUM REQUIRED TENSILE STRENGTH FOR MILL-TYPE STEEL WATER PIPE Steel type Furnace butt-welded Grade A Grade B Grade X 42 Tensile strength <P*1> 45,000 48,000 60,000 60,000 Yield point (psO 25,000 30,000 35,000 42.000 CTD000112 MAY 1967 | M 27 Yield strength is the point at which the steel specimen, under load, will return to its original length when the load is removed. Minimum elongation requirements for seamless and electrically-welded mill-type steel water pipe vary with wall thickness, grade of steel, and welding method. These variations are given in AWWA C2Q2-64T.24 For wall thick nesses of seamless and electrically welded pipe not tabulated in this standard,24 the minimum allowable elongation is calculated according to one of these equations: Grade A Grade B E = 56t + 17.5 E = 48t+15.0 Eq. 17a Eq. 17b Grade X 42 E = 40t + 12.5 Eq. 17c where E = minimum elongation in 2 in. (%) t = tabulated wall thickness (in.) Some manufacturers can supply intermediate diameters and wall thicknesses that are acceptable under these stand ards. Ring deflection. Like other types of pipe material, buried steel water pipe is subjected to compression under external loads that may contribute to ring deflection. Backfill load. Ring deflection is not significantly in fluenced by pipe wall thickness, but it is an important con sideration with respect to the lining thickness. After the steel cylinder thickness has been calculated for factors of in ternal pressure (limited to allowable hoop stress), it is necessary to determine if this thickness, in conjunction with the specified backfilling procedure, will limit ring deflection, caused by external loads, to an acceptable amount. The support offered by soil backfill plays an important part in the proper functioning of a flexible pipe buried under ground. Acceptable deflections that will not damage linings or coatings are based on the following safety factors. Coating and lining Flexible lining and coating Cement-mortar lined and flexible coating Cement-mortar lined and coated Allowable (%) 5 4 2 Tables of predicted percent deflection of the three lining and coating conditions (at 85 and 90 percent backfill com paction), along with formulas and diagrams for calculating ring deflection, have been published.29 Live load. As with other pipeline materials, buried steel pipe is subject to two types of superimposed loads: concen trated and distributed. Below 7- to 8-ft depths, the live-load effect is considered as negligible. For other depths, the equation for superimposed concentrated load is: W = Q,P-^F Eq. 18 where W = superimposed load (lb per lin ft) P = concentrated load (lt>) F = impact factor C, = load coefficient [a function of D/2H and L/2H; H = depth of fill to conduit top (ft); D = outside pipe diameter (in.)] L = effective length of conduit (ft) (use actual length under 3 ft, and 3 ft above 3 ft). Impact factors will vary with vehicle speed, vibration, road way roughness, and depth of backfill cover: Use these values: Depth of cover (ft) 0-i 1-2 2-3 >3 Impact factor (H 1.3 1.2 1.1 1.0 M 28 | WATER AND WASTES ENGINEERING Tolerances. Manufacturing tolerances for mill-type steel water pipe are set forth in brief in Table 27, developed from AWWA C202-64T.24 TABLE 17--MEASUREMENT TOLERANCES FOR MILL-TYPE STEEL PIPE Measurement Max. tolerance Outside diam. <1.9 in. (in.) >1.9 in. (%) <10-3/4 in. (in.)* 12-3/4 to 20 in. (in.)* 22 in. and larger Wall thickness 18 in. or less diam. (% of specified) 20 in. and up diam. (% of specified) Weight Per foot (% variation) Carload lots (% of specified) Length (in.)** Straightness 0.016; -0.031 1.0 -1/64 -1/32 -1/32; +3/32 -12.5; +15.0 -10.0; +15.0 -3.5; +10.0 -1.75 1/8 Reasonable * For 4 in. from end. ** For specified 17-1/2-ft lengths, no length may be less than 9 ft.; for specified 35-ft lengths, no more than 10 percent may be shorter than 26-1/2 ft, and no lengths less than 14 ft; for specified lengths of 20 ft or more, no more than 10 percent may be less than 75 percent of speci fied length, and no length may be less than 40 percent of the specified length. Ends. Tolerances for ends vary with the type of joint to be made, as follows: 24 Joint Plain end for mechanical coupling Specification Square cut, beveled, no burrs Field butt welding Wall thickness of 1/4 in. Bevel inside and out to 30 degrees, with max. plus tolerance of 5 de grees (no minus tolerance); width of root face 1/16 in., with tolerance of 1/32 in. Wall thickness less than Not beveled 1/4 in. Bell and spigot, with rub Difference between outside circum ber gasket ference of spigot and inside cir cumference of bell, min. 0.06 in.; max. 0.20 in. Threaded ends API Spec. S L (Section IX) Other ends By agreement Manufacture The method of fabricating pipe differs according to the type of pipe and the welding process used. Fabricated electrically-welded pipe. This pipe may be produced by automatic welding machines or by manual welding operations, Operators of either process must be qualified under the ASME Boiler and Pressure Vessel Code. AWWA C201-6623 states detailed specifications for plate edge preparation, lap breaking and forming, surface clean ing, fitting up, welding, weld corrections, section rounding, end sizing, end preparation, and automatic and manual welding operations. Pipe ends and seams. Any one of eight types of pipe sec tion ends may be specified. These include four variations for field welding (plain ends for slip or lap joint, plain ends with butt straps, beveled ends with butt straps, and plain or beveled end for field butt welding), plain ends fitted with flanges, bumped ends for field riveting, tapered ends for lap riveted field joints, and bell and spigot ends with rubber gas ket. Longitudinal seams, spiral seams, and girth seams are butt welded. Mill-type steel pipe. As indicated previously, this type of pipe may be furnace welded (continuous butt-welded or furnace butt-welded), electrically welded, or seamless. CTD000113 Furnace-welded pipe. In this process, the pipe may be formed either by bell welding or continuous welding. BeU-welded pipe. In this method of manufacture, pipe is produced in individual lengths from cut-length skelp (the plate or strip of steel from which pipe is made), with its longitudinal butt joint force-welded by mechanical pressure developed in drawing the furnace-heated skelp through a cone-shaped die (welding bell) that serves as a combination forming and welding die. Continuous butt-weld pipe. In the production of small diameter pipe, coiled skelp is formed into continuous-weld pipe at speeds of nearly 8 mph, with the skelp size depend ing on the size of pipe to be formed. The first step consists of unrolling the skelp lengths and welding the ends together to form a continuous strip. The skelp then passes through a furnace, where it is heat ed to about 2200 F, and then through forming rolls, where it is gradually formed and then butt welded to become pipe. From the welding step, the pipe enters a stretch reducing mill where it is stretched to final size (seven pipe sizes can be made from only two skelp widths). The pipe is then marked and cut by a rotary-type hot saw while moving at high speed. After cutting, it moves across cooling tables to the straightening operation, then to crop ping, end-finishing, testing, coating, and preparation for shipment. Electrically-welded pipe. There are two types of electri cally welded pipe: longitudinal-weld (3-1/2 to 36 in.) and spiral weld (6 to 80 in.) Longitudinal weld. This type of pipe is produced in a continuous straight line process. The steel skelp is drawn through a series of vertical and horizontal forming rolls that progressively form the strip of steel into a cylindrical shape. The cylinder then moves through a high-frequency resist ance welder, where the edges are heated to a plastic state. Pressure rolls immediately force the edges together to form a strong continuous weld. After the weld has been accomplished, the pipe cylinder is cooled and then passed through a series of rolls to provide the desired diameter and straightness. Predetermined pipe lengths are cut automatically by a flying cut-off saw. Test ing, coating, Ac., follows. Spiral weld. In this process the steel skelp is drawn from the coil holder and fed to main drive rolls. As the steel en ters the forming rolls, it is spirally wound into a cylinder and automatically welded by the submerged arc process. The pipe then proceeds to a cut-off mechanism and is cut to predetermined lengths. Testing follows. Seamless pipe. This type of pipe is made by piercing a solid steel round bar or billet to produce a rough heavywalled tube. In this process, the bar or billet is heated uni formly to the desired forging temperature. The length and diameter of the billet are predetermined to produce the re quired tube size and weight. Only high quality steel is used. After heating, the billet is pulled, by rolls, over a piercing point and mandrel bar, thus producing a rough tube. Fol lowing the piercing operation, different mills use different methods of rolling, heating, and sizing to produce the final seamless tube. Pipe sizes. The following listing shows the most common ly available pipe sizes for the different types of steel pipe. Type Outside diameter (In.) Fabricated, electrically-welded Mill-type Furnace welded Electrical-welded Longitudinal-weld Spiral-weld Seamless 4 to 144 0.405 to 36 31/2 to 36 6 to 80 2 to 4 Testing Tests performed during manufacture are made in accord ance with standards 2,24 to ensure an acceptable product. Fabricated, electrically-welded steel pipe. As set forth in detail in AWWA C201-66, ** the following tests are made in accordance with the specifications: weld test; free-bend test; root-bend test; nick-break test; and hydrostatic test. The specimens of pipe selected for these tests must meet minimum requirements. Hydrostatic test Hydrostatic test conditions differ for different sizes of pipe. Above 30-in. diameter. The test pressure used for pipes larger than 30-in. diam. may not exceed that given by this formula: where P = test pressure (psi) s = allowable fiber stress (psi) (85 % of yield point of plate). t = wall thickness required for working pressure (in.) D = inside diam. (in.) Below 30-in. diameter. Pipe under 30-in. diam. is tested to specified pressures ranging from 1200 psi in the smaller size to 600 psi in the larger size. The detailed specified pressures are tabulated in AWWA C201-66.** Mill-type steel pipe. The detailed tests that may be re quired by the purchaser on this type are set forth in AWWA C202-647.14 The listing* includes: Ladle analysis (followed by check analyses on drillings or cuttings from pipe) Tensile strength tests (transverse and longitudinal speci mens) Flattening tests (on nonexpanded electrically-welded pipe; nonexpanded resistance-welded pipe; cold-ex panded electrically-welded pipe; and butt-welded pipe 2-7/8 in. and larger) Bend tests for butt-welded pipe Fusion weld tests Hydrostatic tests Hydrostatic test. Each length of pipe is subjected to a hy drostatic test in the mill. Test pressures for different size pipes are specified 24 and range from a minimum of 700 psi for 1/8-in. pipe to a maximum of 2500 psi, with each pipe size having a specified test pressure range depending on the wall thickness and pipe grade (A, B, X 42). Installing pipe line in conduit under railroad. * Many special tests are mill extras and may increase the cost by $20 a ton. Normally, a purchaser will accept the same tests as for "C201 pipe" and avoid these extras. CTD000114 MAY 1967 | M 29 Coating and lining The American Water Works Association has issued two standards for coating and lining steel pipe, one for coal-tar enamel protective coatings28 and one for cement-mortar protective lining and coating.27 Coal-tar enamel. The AWWA standard28 covers corro sion protection for five conditions: Inside of all pipe Outside of all pipe less than 30-in. diam. for underground placement Outside of all pipe more than 30-in. diam. for under ground placement** Outside of all pipe for aboveground placement Outside of all pipe for aboveground placement where corrosive conditions exist Material. The AWWA standard28 sets forth the specifi cations for the several materials used in connection with this protective coating. These materials include: primer, coal-tar enamel, white wash, synthetic red lead primer, synthetic white enamel, aluminum bronzing pigment, cold-applied coal-tar coating, and cold-applied coal-tar emulsion asbestos felt wrap, fibrous glass mat wrap, and sand shield. Primer. Two types of primer are used: Type A (coal tar) and Type B (fast-drying). Enamel. The coal-tar enamel used must be specially proc essed coal-tar pitch and must not contain any petroleumor natural-base asphalts. It must meet rigid maximum and minimum specifications for physical characteristics set forth in the standard.28 The following tests are conducted to de termine if the characteristics meet the standards: high-tem perature test, low-temperature test, deflection test (initial heating), deflection test (after 2-hr heating), peel, initial bond, bond after 72 hr, impact test (direct and indirect). Aboveground coatings. When steel pipe is installed above ground, it is given two primer coats of red lead pigment in a synthetic-resin vehicle. If exposed to or installed during hot weather, the second primer coat is synthetic white enamel. Application of coal tar. Primers and enamels are applied in the shop, but some application is necessary in the field to protect joints and to repair damage to the coating during handling. Shop application. When coatings are applied in the shop, the pipe surfaces are cleaned and, if necessary, warmed to 8S to 100F; primer is added by hand brushing, air-gun spraying, or spraying and brushing. The prime-coated pipe must be protected from moisture, dust, etc. After the primer has dried for the specified time, the coal tar, which has been heated to the proper temperature, is applied to the pipe. For coating the inside of the pipe, the enamel is applied by centrifugal casting. Either of two application methods may be used: trough method, or re tracting weir, i.e., feed-line method. Details of those methods appear in AWWA C203-62.28 Coal tar is applied to exterior surfaces by pouring the heated material onto the pipe as it revolves, making certain that each spiral of applied coating overlaps the next, and that the coating is continuous, free from defects, and 3/32 1/32 in. thick. Electrical inspection with a flaw detector operating at 8000 to 10,000 v (and low amperage) is used to check for holidays in the coating. Field application. Coated pipe must be handled from shop to installation with care to prevent damage to the coating. In the field, both interiors and exteriors of joints must be inspected for damage and repaired. ** This procedure is not generally followed today. Nearly all pipe is coated and wrapped in a manner similar to the standards for pipe 30 in. and less. M 30 | WATER AND WASTES ENGINEERING Application of aboveground coating. Exterior surfaces of pipe installed aboveground are cleaned and coated according to specifications in the AWWA standard.28 For ordinary service in a noncorrosive atmosphere, two coats of red lead primer (or one coat of synthetic red lead and one coat of synthetic white enamel) and one coat of aluminum bronze paint are applied. For corrosive atmospheres, the steel surface receives one coat of heavy-bodied, cold-applied coal-tar coating, one coat of heavy-bodied coal-tar emulsion, and one coat of alu minum paint. Additional exterior coating. Where additional exterior coating is desired on pipe to be placed underground, the coating process consists of a coat of primer, followed by a hot coat of coal-tar enamel onto which is bonded a single layer of asbestos felt wrap, followed by one coat of waterresistant white wash, or a single wrap of kraft paper. Coaltar enamel and bonded double-asbestos felt wrap may be called for where extraordinarily severe soil conditions exist or for submarine lines and river crossings. Another type of wrap that may be used for these severe conditions is a coaltar enamel, fibrous-glass mat, and bonded asbestos felt wrap. A sand shield (i.e., bedding and immediate backfill) may be used in severe soil conditions. A reinforced cementmortar shield for additional protection may be required in some areas. This shield is covered in AWWA C205-62T.27 Mortar lining. Specifications for cement-mortar lining and coating are covered in AWWA-C205-62T.27 Pipe surfaces to which cement-mortar is to be applied must be clean, and the mortar used must be proportioned correctly by weight (3 parts sand to 1 part cement, with a maximum water-to-cement ratio of 0.5 to 1.0, by weight). Materials used should meet the specifications in Table 28. TABLE II--SPECIFICATIONS FOR MATERIALS FOR CEMENT-MORTAR LINING AND COATING OF STEEL WATER PIPE Materia Specification Cement Type II, ASTM C50 Sand Inert, hard, strong, durable, and uncoated; free from dirt, with no more than 1% shale, 1% clay lumps, and 3% mica (maximum allowable dele terious substances, 5%) Water Clean, colorless; no objectionable amounts of organic matter, alkali, or salt Sealing ASTM Des. C309; may riot impart taste or odor to compound water after drying Paint 4-hr-drying, corrosion resistant, with good bond ing characteristics Straight sections are lined by rotating the pipe in a special machine with the mortar applied centrifugally to the inside of the pipe. Specials are lined by mechanical or pneumatic placement, or by hand trowelling, and finished to produce a smooth, dense surface. < Acceptable mortar lining thicknesses are given in Table 29. (Note: Linings and coatings covered by AWWA Stand ards C203 and C205 can be used interchangeably, that is, the pipe can be cement-mortar lined and coal-tar enamel coated or coated and lined with any other desirable com bination. ) TABLE II--THICKNESS SPECIFICATIONS FOR CEMENT-MORTAR LINING FOR STEa WATER PIPE Plpo size (In.) 4-10 11-23 24-36 >36 Thickness (In.) 1/4 5/16 3/8 1/2 Tolerance (in.) 1/32 1/16 1/16 1/16 CTD000115 r Curing. Immediately after the mortar is applied, the pipe ends are closed to prevent drying of the lining, and within 1 hr thereafter, the pipe lining is subjected to curing by either water or steam. Water curing. This treatment consists of keeping the lin ing moist and within temperature limits, by sprinkling heads or other methods, for a period of 7 days before shipment. If exterior coating is to be applied, the application is made after 24 hr of curing, and the pipe is then cured for 6 days more. Steam curing. This treatment consists of introducing steam into the pipe and making certain that the temperature of the pipe is maintained between 130 and 150 F for a pe riod of at least 42 hr. Mortar coating. External protection of steel pipe is pro vided by a mortar coating. The cement-mortar (3-1/2 parts of sand to 1 part cement by weight, with controlled water content) is applied, over reinforcing, by mechanical place ment or by the steam-pneumatic process. Application by the air-pneumatic (gunite) process is permissible, with the mor tar composition limitation being 4 parts sand to 1 part ce ment, and controlled water content to prevent sag, run, or segregation of the mortar. The material used for the coating should be the same as that given in Table 28. Mortar thickness. Exterior coating thickness is usually specified to meet the limitations given in Table 30. TARLE M--THICKNESS SPECIFICATIONS FOR CEMENT-MORTAR C0ATIN0 FOR STEEL WATER PIPE Pip slza (in.) 4-12 13-19 20 and up Ttilcfcns* On.) 1/2 5/8 . 3/4 Tolrnc (In.) +1/8 +1/8 +1/8 Reinforcement. Cement-mortar coatings must be rein forced. The reinforcing may be by spiral wire, wire fabric, or wire mesh (ribbon mesh), specified as follows: Typ Spiral wire Wire fabric Ribbon mesh Gag* 15 13 18 17 Max. spacing (In.) 11/4 2X4 1X1 1-1/2 X 1-1/2 ASTM Das. A-82 A-185 A-82 A-82 Machine coating. When application is by mechanical or pneumatic placement, the coating may be applied in cours es, but the application time interval between first and last course may be no more than 2 hr. The AWWA standard29 places restrictions on such factors as support and interrupt ed placement, particularly with Vespect to spiral-wire and wire fabric or ribbon mesh reinforcement. Curing. Cement-mortar coatings must be cured after the initial set. The water curing process (see linings, above) may be used (minimum curing period--7 days); or steam curing (as with linings) may be used (minimum period--42 hr). Field joints. For inside joints, the cement mortar for field joints should be composed of 1 part cement to 2 parts sand, dry-mixed, and moistened just enough to make troweling and calking possible without crumbling. For outside joints, the mortar is composed of 1 part of cement and 3 parts sand, with sufficient water to provide a flowing consisten cy. Details of application for different size pipes are given in AWWA C205-62T.27 Section 6--Wood-stave Pipe Wood-stave pipe is not used in water distribution systems but is used in large-diameter transmission lines, particularly for industrial or power plants located in rough terrain, where the pipeline is usually located above ground. This type of pipe has certain advantages: light weight, fairly long life, high carrying capacity, corrosion resistance, and ease of construction in difficult locations. Design There are two types of wood-stave pipe, continuous stave and machine-banded. Both may be made in any desired di ameter up to 20 ft and for pressures up to 150 psi. Wood-stave pipe is designed to resist internal bursting pressure but not external flexural stress, although the latter may have some importance if the pipe is installed in a trench and backfilled. In addition to internal pressure, the diameter and spacing of the bands are important design factors. The latter two are interdependent. Generally, the band diameter is determined first to develop the full crushing strength of the wood. Then the spacing is determined. Equations relating stress to pipe diameter, wood-stave thickness and strength, and band radi us and strength, etc. are used to calculate the band diameter and spacing. Manufacture Continuous-stave pipe is usually manufactured in cradles at the site. Staves are laid together in such a way that joints between staves are staggered. Joints are planed radially and may have a copper or zinc plate between the stave ends to make them water tight. These joint "gaskets" are used be cause longitudinal swelling of the wood stave is small. Wire bands are placed around the pipe and spaced as cal culated, but never more than 12 in. apart. The bands are held firmly in metal shoes, which are connected by bolts that apply the required tension. Continuous stave pipe is usually made in one continuous length. It can be curved without difficulty on a minimum radius of 50 times the pipe diameter. Machine-banded pipe is usually factory made and shipped to the site. The staves are held together by ten sioned spirally wound steel bands. Pipe lengths, usually lim ited to 20 ft for ease of handling, are joined by collars placed around the outside of the pipe, or by means of re cessed or tenon joints. Recessed joints are suitable only for low pressure. Collars may be of wood stave, cast iron, or steel. Connections to wood pipe are generally made by special iron castings fastened to a saddle held in place by iron bands. Section 7--Wrought Iron Pipe One of the earliest recorded uses of wrought iron pipe in water systems is that of some 12,500 ft of small diameter (lVi and 2-in.) laid in Alexandria, Va., in 1852. More than a third of this pipe was still in use a century later. Another early use was in San Francisco, where more than 250,000 ft of large diameter pipe (23- and 20-in.) was in stalled in the 1860s. About half was still in use 80 years later. Probably the most historical installation of OD wrought iron pipe was in a portion of New York City's Croton Aq ueduct, built under the Harlem River in 1860 and still in service. It was constructed of Vi-in. wrought iron plates, fabricated to form a 90-in. pipeline. Another historical installation of interest is the 21 mile, It Vi-in. wrought iron pipeline installed in 1873 to bring water to famed Virginia City, Nev., site of the Comstock lode. Much of the line is an inverted syphon that carries CTD000116 MAY 1967 | M 31 water 2000 ft down one side of the Washoe Valley and up 1600 ft on the other side. Although the population has dwindled from more than 15,000 to less than 1000, the sy phon is still in service. Wrought iron pipe also finds wide use for inplant sys tems, for submarine lines, cooling lines, well casings, heating and plumbing systems, and electrical conduits. Design Wrought iron is a two-component material consisting of high-purity iron and iron-silicate (slag). The silicate (about 2Vi percent of the total weight) is not chemically combined with the iron. Rather, it is physically distributed throughout the iron (Fig. 15) and gives the iron a distinctively fibrous structure, similar to that of green wood. Characteristics. Wrought iron possesses qualities of tough ness, ductility, malleability, mechanical strength, weldabil ity, and corrosion resistance. These characteristics stem al most wholly from the even distribution of silicate fibers, of which there are approximately 250,000 in each cross-sec tional square inch (see Fig. 15). when the latter process was introduced in this country. There are three basic steps in the manufacture of wrought iron: melting and refining of the metallic iron or base metal; production of a controlled iron silicate slag; and mechanical incorporation of the refined iron into the iron silicate slag by pouring melted iron (2900F) into molten slag (2500F). The temperature of the molten slag is a few hundred degrees lower than that of the molten iron at the time the two are mixed. This causes the iron to solidify rapidly as it is poured into the liquid silicate slag. Rapid solidification of the refined iron causes dissolved gases to be liberated with such force that the metal shatters into small fragments. This results in the formation of a 3- to 4-ton "sponge ball." Rolling this ball into a bloom causes the iron silicate to elongate in the direction of rolling. Microscopic inspection (Fig. 15) shows the glass-like iron (nonrusting) fibers. Pipe sizes. Wrought iron pipe from V* to 4 in. is produced on a special machine that utilizes a continuous weld system. Sizes from 4Vi- through 14-in. are lap-welded. These pipe sizes are threaded for couplings or flanges. Table 32 shows pipe sizes and physical data up to 14-in. diam. pipe. Large OD pipe (above 14-in. diam.) is produced from plates of desired size and thickness by fusion welding. Table 33 lists physical data for pipes 14-in. in diameter and above. Coating and lining. Wrought iron pipe may be specified with either of two types of protective coatings, metallic or nonmetallic. Hot dip galvanizing is a very popular coating process. Nonmetallic coatings range from cement mortar to simple paints. Some wrought iron pipe manufactured for distribu tion system mains is cement-lined. The method of applica tion of cement lining is the same as that used in cast iron pipe manufacture. Handling and shipping. Wrought iron pipe should be handled with the same care given to other pipes, especially if the pipe is coated or lined. Shipping practice is similar to that for other pipe; i.e., truck or rail. S' These glass-like fibers form a defense against corrosion and force it to to disperse, thus preventing deep pitting and penetration of the pipe. Wrought iron can be welded easily by any electric or oxyweld method. It can readily be bent formed, hot or cold, by hand or machine, merely by following good bending prac tices. Because of the presence of the silicate fibers, the surface of wrought iron is rougher than that of other mate rials. This rougher surface provides a better anchorage for galvanizing or for nonmetallic coating. Typical wrought iron contains the following substances in the amounts indicated: carbon, 0.03 percent maximum; manganese, 0.06 percent maximum; phosphorus, 0.120 to 0.140 percent; sulfur, 0.15 percent maximum; silicon, 0.10 to 0.20 percent; and iron silicate slag, 2.50 percent. Physical and mechanical properties. All wrought iron pipe, including that made from plate, must meet recognized engi neering standards. ASTM Des. A-419 covers the fabrication of large OD pipe, and wrought iron plate is manufactured in accordance with ASTM Des. A-42. Typical physical de sign properties under these ASTM Designations are given in Table 31. Wrought iron pipe may also be specified in accordance with Federal Specification WWP-441, and welded tubing according to Military Specification MIL-T-17168 (NAVY). Manufacture Wrought iron is manufactured either by hand puddling or by the Byers-Aston process. The former method was used in both the United States and Britain until about 1930, TABLE 11--TYPICAL PHYSICAL PROPERTIES OF WROUGHT IRON* Property Pipe A-72 Plot* A-42 Tensile strength, min. (psi) Yield strength, min. (psi) Elongation in 8 in., min. (%) 42,000 25,000 12 48.000 27.000 14 Weight (Ib/cu ft) Specific gravity Modulus of elasticity (psi) Shear strength (psi) Shear modulus (psi Tension modulus (psi) Poisson's ratio Hardness, Brinell Hardness, Rockwell Impact, strength Standard Charpy, keyhole notch, double refined rounds (ft/lb) Standard Izod, Izod V-notch (double) refined rounds (ft/lb) Modified Charpy, Izod V-notch (double) refined rounds (ft/lb) Modified Charpy, Izod V-notch, plate (ft/lb) Melting point, approximate (F) Specific heat (BTU lb/F) Thermal conductivity, K (BTU in./hr/sq ft/*F) At 64*F At 212F Mean coefficient of thermal expansion, (68-200"F) (in./in./F) Electrical resistivity at 69.8F (ohms cm/sq cm) 480 7.70 29 X 10 46,000 11.8 X 10* 29.5 X 10 0.30 97 to 105 B55to B60 24 to 28 50 to 60 70 to 85 40 to 44 2750 0.11 417.89 414.99 7.4 X 10X` 11.97 'Properties at G8F unless otherwise stated. M 32 | WATER AND WASTES ENGINEERING CTD000117 TABLE 32-- PHYSICAL DATA OH PIPE SIZES TO 12 IH. r = *m oooooot3,oooo^-ooc^ rH^tuiroror^^Hm>-i (N2rsirs2CNirgcvj<rrrf'3- Mfoio^oininoino vOX3 M--4lf1--tOLONOCIO-- fOoOMlOON = r; * 1^ seftusi.*T oooooooooo mMMmCmOi'oOorooroonofOoNor' <\J CM CM Csl cncoconnooooomrvCM O-ff HOlOONfOVDN riHOjmmifiNONin C0T9iHr-rO--.oIO<`OOC(MOLOOUJ'TIA--'O(^O HrHMrof'iinpsorj'T -CE ^c iHm-Hnr-ro.lPHoOoNUiNO"jN^NroroO<o\rjotOoNinM^^ oooooooooo Orifo>lrVroO-roOio>OaC*M--p<^gCOTMl<r--OooOCoW~f.nOotH--o< ooOHHHtvjojmro *;E^ knc oomoominooo in H(i o i-- r- o o o oooroooroooinoin OHHr<r 1 cm cm co H CO -- *--< 00 OO ^ CO CM Old hhhhhpoh -^.-HCMCMCMrvirocornco cocOLOOOOOOinO IOCfHoNmOo<OvUjrIU*TcO\ioNoOo r-lHHHMNm i --.i A gt o SSS.3S OoOoOoOoOoOoOoOoOoOo r-.r-r-.ooooooMCN < *--i oo co co co IflMCOCOmODMNOC' CO H CM I-- OCOOCNJOO o i- r-< cvj cm ro in <n o I II "tl :? mcnairv(\unoioOr-<iji cor-icO(\ir-'ix>r-'in>-irv OrHHMWMlONClO >>>vccc cc ^i-m(^Omm<CTOnMfiOoONrmHHMT !.-<.-H-4CMrMCMCM oooooooooo nHH42N<rOtr0oOo)loOiranlHo iocooroioo4f OiOO O o "-1-H O.J (M M m 42 ^Eo UKJ =<Q C w 0010 001^(0000 <ru`}--<oor-~r--ooo coocoocncoooinoin Eg~ o._ C Z "w in cnj cm^ 4 H eg c\i m rc r CTD000118 Material Asbestos-cement Brass Cast iron Copper Galvanized iron Lead Plastics ABS PE PVC Steel Wrought iron TABLE 14--DATA ON SERVICE LINE MATERIALS Type Standard no. Red seamless Regular Extra strong AWWA C400-65 AWWA H3 ASTM B43-47 Flex ible Rigid V Size range (in.) 3, 4, 6 V 1/2 to 6 1/2 to 6 Gray AWWA C102 V 2, 3, 4, 6 Type K! AWWA C800-55 V ASTM B88-47 1/2 to 6 V 1/2 to 3 AA (XS) AAA (XXS) AWWA C800-50 V CS 95-41 3/8 to 2 Weight range1 (ib/tt) 0.93-19.0 Working pressure (psi) Class 100, 150, 200 12-30 Class 50, 100, 150, 200 0.344-13.9 2.0-19.5 75 100 Comments Noncorrosive; not available below 3-in.; slip coupling joints Longlife under normal conditions; corrodes in acid soils; uses threaded coupling joints; re quires gooseneck connection Corrosion resistant when lined and coated; not available in small diameters; rigidity and short length require joints and goose neck connection Direct connection to mains; cor rosion resistant; dissolves in soft water with high CO* content Not highly resistant to corrosion; requires threaded joints and gooseneck connection Direct connection mains; corro sion resistant except in soft waters with high . COj; some tendency to creep or crack un less properly formulated 1 l ] Black or gal vanized Cement-lined CS 254-63 ASTM D2282-65 USASI B72.3-67 CS 255-63 ASTM D7239-65 USASI B72.1-67 CS 256-66 ASTM D2241-65 USASI B72.2-67 ASTM A120-47 Fed. Spec. WWP-406 V Black or gal ASTM A72-95 vanized ASTM A90-39 V 1/2 to 6 0.05-2.8 40-160 V 1/2 to 2 0.07-1.8 80-160 0.16-3.2 V 1/2 to 6 160-300 V 1/2 to 6 0.85-53.16 200 V 1/2 to 6 1/2 to 6 0.85-53.16 200 All sizes not available in all types and all pressure ratings; all types will resist limited number of freeze-thaw cycles; will hold pressures up to 150-160F. Check with manufacture for available sizes and pressure ratings Available in three grades: strong, extra-strong, double extra strong. Weight per foot range covers three grades; not resist ant to corrosion unless cementlined Same comments apply as for steel * Weight per foot varies with material, type, wall thickness, etc. * Type L specified by Copper Development Association "Copper Tube Handbook." * See Part 2, Section 4 of this manual. Section 8--Service Lines According to AWWA Manual M8,7 "The most impor tant factor affecting the useful life of service lines is the ability of the material used to resist internal and external corrosion." Internal corrosion, either pitting or tuberculation, adversely affects the carrying capacity of the pipe. Ex ternal corrosion may result in leakage. Table 34 lists the most commonly used materials, the more important pertin ent physical characteristics, and advantages and disadvant ages. An AWWA Committee Report published as a part of AWWA C800-5528 covers current standards for certain types of service line materials. Hydraulic-flow characteristics are good on all newly in stalled pipe and remain so on lines of asbestos-cement, copper, lead, and plastics. More detailed information on the characteristics of asbestos-cement, cast iron, plastics, steel, and wrought iron is presented in previous sections of Part 2. Flexible materials can be connected directly to the corpo ration cock in the main and to the stop-and-waste valve in side the foundation wall of the house. Nonflexible materials require a flexible "gooseneck" connection to the corpora tion cock and sometimes may need a flexible connection to the house plumbing system. Gooseneck connections may be lead, copper, or flexible plastic. Flexible materials are not damaged by freezing, but electrically-nonconductive materi als, when frozen, cannot be thawed electrically. Relative costs of these various materials are not com pared in Table 34. Costs vary, not only with time, but also with location, point of manufacture, installation conditions, and other local factors. Inasmuch as the cost of installing service may exceed 10 percent of the total investment of a water utility, it is important to select service line materials that will provide the longest possible effective service. Selec tion should be made only after consideration of all data. Section 9--Inplant Systems As indicated in Table 8, almost every type of material used in water systems may be and is used for all types of inplant systems piping, including lines for air, chemical feed, filter influents, effluents, and wash lines, gas, heat, high and low service, plumbing, pump suction and dis charge, and sampling. Pipe materials used in inplant systems have the same design and are manufactured by the ',irae process as ma terials used for distribution and service lines. With the ex ception of glass and rubber, these materials have been dis cussed in previous sections of Part 2. Pyrex glass has been used for chlorine gas and solution lines, a notable example being the Chicago Central District Filtration Plant. These lines are rigid, and require support and special fittings. Copper is also used where flexible chlorine connections are required. Hard rubber and iron are used for conducting liquid chlorine under pressure. Flexible rubber lines are also used to handle chlorine so lutions and to transport other solutions, carbon slurries, etc. Inplant piping systems, particularly of large size pipe used on high- and low-service lines, usually utilize flanged joints. Other types of joints may be used, depending on line size, material, and application. M 34 | WATER AND WASTES ENGINEERING CTD000119 /water and wastes engineering MANUAL OF PRACTICE NUMBER TWO WATER SYSTEMS Section 1--Transmission and Distribution Several operations in the installation of transmission and distribution lines are the same regardless of the pipe materi al used. Therefore these operations will be discussed here without reference to specific materials, except as may be necessary. The American Water Works Association has is sued standards for laying asbestos-cement pipe28 and for laying cast iron pipe,30 for rubber gaskets for cast iron pipe, 31 and for field welding of steel pipe joints.32 Pipe handling All pipe receives a final inspection before shipment. Care is taken to make certain that every length leaving the manu facturing plant is in first-class condition. Damage from rough handling in transit will occur occasionally, so pipe should be inspected when it arrives or as it is being unload ed from the railroad car or truck. Rough treatment in trans it is usually evident from broken tie straps or wrecked wooden blocking placed at the factory. Metal pipe can be checked for in-transit damage by "ringing" each length with a hammer. Failure to ring properly indicates damaged pipe, which should be reported to the manufacturer and rejected for use. Fig. 16. Method of unloading pipe with snubbing ropes and skids. Unloading. Handling includes unloading from the trans porting vehicle (railroad car or truck). Small diameter pipe may be unloaded by derrick. Large diameter pipe should be unloaded with the aid of skids and snubbing ropes using a rolling hitch at each end (Fig. 16). Pipe unloaded on skids should never be rolled against other pipe. When pipe is unloaded to storage, it should be stacked ac cording to the manufacturer's directions, with the stack height controlled within the limits of safety and practicality, and with blocking as necessary. Belled-pipe is stacked with the bells at right angles in each layer. For smaller pipe di pipes and piping PART 3/ INSTALLATION PRACTICES ameters, the maximum number of layers is ten; for larger diameters, the maximum is less; the maximum practical stack height is 12 ft. In the delivery of small diameter pipe to be laid by hand, the pipe lengths should be strung along the route. (Belledpipe should have the bells facing in the direction the work is to proceed.) The method of unloading pipe from trucks or cars may utilize a derrick and cable with hooks for engaging each pipe end. Hooks for handling lined pipe should be rubber cov ered. Both small and large-diameter pipe may be handled by sling, hooks, or by skids and snubbing ropes. Some types of pipe may be handled by fork-lift truck. Stringing pipe. To avoid unnecessary handling, both pipe and fittings should be placed as near as possible to their final location in the line, with due respect to the safety of the traveling public. Pipe should be placed as close to the trench site as possible and on the side opposite that where the excavated dirt is to be piled. Asbestos-cement pipe is usually not strung along the trench line in advance of laying operations but is delivered from storage to trench site as needed. When pipe is to be moved only a short distance, it should be rolled by hand or moved by hoist; it should never be pushed by bulldozer blade. Pipe with a special exterior coat ing should be handled by canvas belt sling or special cable around the middle of the pipe. Patented lifting tongs are also available for handling pipe by hoist and cable. Whenev er rubber gaskets are to be used in pipe joints, they should be stored out of direct sunlight and protected from dirt until needed. Detailed directions and precautions for handling, storing, and stringing pipe along the right-of-way may be obtained from the manufacturer or from the pipe manufacturing as sociations. Trenching Water mains are generally installed to a definite line and grade as established by the project engineer. This is particu larly true where other subsurface utilities are located in the streets. The trench itself may be dug by hand or by excavating machine. Earth trenching employs one technique, rock ex cavation, another. Solid rock must be blasted. Trench depth. Generally the designing engineer specifies the trench depth or, more particularly, the depth of cover over the pipe after the trench is backfilled. The amount of cover specified usually depends on the frost line in northern states (minimum cover 5 ft) and on the surface load condi tions in southern states (minimum cover VA to 4 ft). Sometimes the pipe is laid aboveground, as for example, the pipeline from Hollywood to Key West, Fla., long transmis sion mains in the west, and on bridges over water. Some times pipe is laid in subaqueous trenches across rivers, har bors, and lakes. Laying subaqueous lines requires special underwater excavating equipment, divers, and special laying techniques. The trench should be as shallow as possible and still pro vide for frost protection and surface loading. Deep trenches are costly; they require shoring and bracing and are often CTD000120 MAY 1967 | M 35 wet, a situation that requires pumping. Standard pipe selec tion tables are based on pipe installed with a S-ft cover, with the pipe laid on a flat-bottom trench, and with the backfill tamped to the centerline of the pipe. Trench widths. The width of the trench should be suffi cient to permit proper installation df the pipe, with room for the workmen to make up the joints and to tamp backfill under and around the pipe. Trench widths are governed by type of soil, pipe size, and excavating equipment. Most trench specifications allow the trench width to be 1 to 2 ft more than theoutside pipe diameter. For asbestos-cement pipe, the following widths are sug gested. Pipe diam. (in.) 4 6 or 8 10 or 12 14 or 16 Min. (In.) 18 20 24 30 Trench width Max. (In.) 28 32 36 42 For cast iron pipe, the suggested trench width for pipe 4 to 18 in. in diameter is the pipe diameter plus IS in.; for pipe 20 to 60 in. in diameter, the suggested width is the pipe diameter plus 18 in. Suggested trench widths for concrete pipe are as follows (where D is inside diameter of pipe). Pipe diam. (In.) 16,18,20 24 30, 36 42 48 Trench width Min. (In.) Max. (In.) D + 12 D + 22 D + 13 D + 23 D + 14 D + 24 D+ 15 D + 25 D-F 16 D + 26 Wide trenches for small diameter pipe should be avoided, particularly in hard clay soils. The weight of backfill in a wide trench is out of proportion to the beam strength of small pipe. For example, if the specifications call for a trench width of 4 ft, and if the trench is actually 5 ft wide, the load on the pipe could increase by 56 percent. The ex cess load is not in direct relation to the change in the pipe diameter-trench width ratio. Pipe laid in a curve. Where pipe is to be laid on a curve, it will utilize the available deflection characteristic of the joint. For such situations, the trench width will be some what wider than normal. The offset of pipe and radius of permissible curve for asbestos-cement pipe are given in Table 35, for cast iron pipe in Table 36,83 and for concrete pipe in Table 37. TABLE IS--OFFSET OF PIPE AND RADIUS OF PERMISSIBLE CURVE FOR ASBESTOS-CEMENT PIPE Degree deflection i 2 3 4 5 3-1/4 Offset Radius (In.) (ft) .7 187 1.4 93 2.0 62 2.7 46 3.4 37 Pipe length (ft) 6-1/2 Offset (In.) 1.3 2.7 4.0 Radius (ft) 374 186 124 5.4 93 6.8 74 13 Offset (In.) Radius (ft) 2.7 748 5.4 372 8.0 248 10.8 186 13.6 148 TABLE IS--MAXIMUM DEFLECTION FULL LENGTH CAST IRON PIPE" Pipe (In.) Define. (des) Approx, radius of curve (ft) produced by succession of Max. daflec. (in.) for pip* joints for pipe lengths (ft) of lengths (ft) of 12 16 18 2b 12 16 18 20 PUSH-ON TYPE JOINT 2 2-1/4 3 4 6 8 10 12 14 16 18 20 24 30 36 42 48 5 12 5 12 5 12 5 5 5 5 5 3 3 3 3 3 2 2 2 2 17 19 21 140 185 205 230 17 19 21 140 185 205 230 17 19 21 140 185 205 230 17 19 21 185 205 230 17 19 21 185 205 230 17 19 21 185 205 230 17 19 21 185 205 230 17 19 - 21 185 205 230 10 11 12 300 340 380 10 11 12 300 340 380 10 11 12 300 340 380 10 11 12 300 340 380 10 11 12 300 340 380 6 7-1/2 8 450 510 570 6 7-1/2 8 450 510 570 6 7-1/2 8 450 510 570 6 7-1/2 8 450 510 570 MECHANICAL-JOINT PIPE Bend in one joint angle fdea-min) 3 8-18 21 28 31 85 110 125 4 8-18 21 28 31 85 ,110 125 6 7- 7 18 24 27 100 130 145 8 5-21 13 18 20 130 170 195 10 5-21 13 18 20 130 170 195 12 5-21 13 18 20 22 130 170 195 220 14 3-35 9 12 13-1/2 15 190 250 285 320 16 3-35 9 12 13-1/2 15 190 250 285 320 18 3- 0 7-1/2 10 11 12 230 300 340 380 20 3- 0 7-1/2 10 11 12 230 300 340 380 24 2-23 6 89 10 300 400 450 500 30 2-23 6 89 10 300 400 450 500 36 2- 5 5 78 9 330 440 500 550 42 2- 0 5 6 7-1/2 8 340 450 510 570 48 2- 0 5 6 7-1/2 8 340 450 510 570 TABLE 17--DEFLECTION DATA ON CONCRETE PRESSURE PIPE1* Offsets (in.) Pipe Half-bevel Bevel Angles (deg) Pipe Half-bevel Bevel Grade change (%) Pipe Half-bevel Bevel 16 0 to 5-1/4 7-3/4 to 18-1/4 0 to 1-1/2 2-1/4 to 5-1/2 0 to 2.7 4.0to 9.5 IS 0 to 4-1/2 9-1/4 to 18-1/2 0 to 1-1/4 2-3/4 to 5-1/2 0 to 2.4 4.8to 9.6 20 0 to 4-1/4 3-1/4 to 11-1/2 10-1/2 to 18-3/4 0 to 1-1/4 1 to 3-1/2 3 to 5-1/2 0 to 2.2 1.6to6.0 5.4to 9.8 Pipe diameter (in.) 24 30 0 to 3-1/2 3-1/2 to 10-1/2 10-1/2 to 17-1/2 0 to 2-3/4 4-1/4 to 9-3/4 11-1/4 to 16-3/4 Oto 1 1 to 3 0 to 3/4 1-1/4 to 3 3 to 5-1/4 3-1/4 to 5 Oto 1.8 1.8to 5.5 5.5to 9.1 0 to 1.5 2.2 to 5.1 5.8to 8.8 36 0 to 2-1/4 4-3/4 to 9-1/4 11-3/4 to 16-1/2 0 to 3/4 1-1/2 to 2-3/4 3-1/2 to 5 Oto 1.2 2.4to 4.9 6.1 to 8.5 42 0 to 2 5 to 9 12-1/4 to 16-1/4 0 to 1/2 1-1/2 to 2-3/4 3-3/4 to 4-3/4 Oto 1.1 2.6 to 4.8 6.3 to 8.5 48 0 to 3/4 5-1/4 to 8-3/4 12-1/2 to 16 0 to 1/2 1-1/2 to 2-3/4 3-3/4 to 4-3/4 0 to 0.9 2.8 to 4.6 6.5 to 8.3 * Deflection in any length of pipe can be obtained by opening the joint. The offsets In this table are based on.f 1/2 m. on a 16-ft length. For 20-ft lengths, increase offsets by 25 percent. The long and short sides of elbows and bevel pipe are indicated by punch marks on the end ofthe spigot ring. Half and full bevel adapters have same deflection as beveled pipe. W M 36 | WATER AND WASTES ENGINEERING CTD000121 Fig. 17. Examples of trench sheeting. Left, open; center, closed; right, movable shield. Excavation. Whether excavation is by hand or by ma chine, the excavated soil is piled on one side of the trench at a distance sufficiently away from the trench wall to prevent excavated material from rolling back into the trench, and also to allow room for walking along the trench. The pipe is strung out on the opposite side of the trench. Rock excavation. The term "rock" applies to solid rock, ledge rock, and to loose boulders more than 8 in. in diame ter occurring in large gravel formations. In any type of rock formation, the rock must be excavated to a level 6 in. below the grade line of the pipe bottom (see Bedding). Excavated rock should be hauled away and not used for backfill. Bad soil. Where soil conditions are bad (e.g., coal mine debris, cinders, sulfide clays, mine tailings, factory waste, or garbage), the soil should be excavated to a depth 6 in. below the grade line for the bottom of the pipe (see Bed ding). All excavated bad soil should be hauled away and not used for backfill. Sheeting and bracing. Whether or not the sidewalls must be protected against cave-in depends on soil conditions and trench depth. This protection is accomplished by the use of sheeting and bracing (see Fig. 17), and serves not only to prevent delays in pipe laying, but also as a safety measure to protect both the workman and the public. Many cities have established regulations for sheeting and bracing based on local soil conditions, as determined from experience. Bedding. All types of pipe must be supported properly by the trench bottom. Pipe can be laid directly on the trench bottom if the bottom has been leveled properly. A leveling board should be used to ensure that there are no voids or high spots and that the grade is correct. Any high spots should be shaved off, and voids should be filled with well tamped soil. For greater load-bearing ability by the pipe, the trench bottom may be hollowed out to conform to the contour of the pipe circumference. This method of bedding is used in special cases. Usually, the design engineer specifies the type of bedding, including tamped backfill (see Backfill). Asbestos-cement pipe may be laid directly on the trench bottom or on earth pads (see Joint holes and Backfill). Special bedding. For pipe laid in rock, bad soil, or soft or wet soil, special bedding must be provided. In rock soil areas, the rock is excavated to a depth of 6 in. below the grade line for the bottom of the pipe. The trench bottom is then built up with a 6-in. bed of sand or good soil free of clods, placed, leveled, and tamped to grade. In bad soil areas, the material is excavated 6 in. below grade and replaced with sand or good soil. Where soils are soft or wet, the ground may have inade quate bearing. In such areas, either crushed stone or gravel should be used to support the pipe throughout its entire length. In extreme situations, pile supports and stringers may be utilized. Joint holes. Where pipe lengths are joined together, pro vision is made in the trench to allow proper jointing with the type of joint employed. Asbestos-cement pipe joints. Where the pipe is directly on the trench bottom, a coupling hole is dug at the joint loca tion; the hole is 3 in. deep and 6 in. longer than the cou pling. Instead of using coupling holes, the pipe may be laid on two earth pads. 12 in. wide, minimum 2 in. high, and full trench width. These pads are located 31 in. from each end of a 13-ft length, or one-fifth of the pipe length from each end for shorter pipe lengths. These pads should be made of tamped good backfill material, free of stones, lumps, or other hard material. Pipe should be firmly positioned on these pads and aligned for coupling. The space between pads is backfilled later (see Backfill). Cast iron pipe joints. For cast iron pipe joints of the bell and spigot type, which are to be made up with lead calking, the trench is excavated somewhat wider and deeper at the joint location to allow room for the calker to work. Cast iron pipe utilizing the slip-on type of joint requires no extra trench width but does require the trench bottom to be excavated below grade sufficient to receive the bell and to make certain that the remainder of the pipe length rests solidly on the trench bedding. Mechanical joints require no extra trench width at the joint location and only a hole in the trench bottom ,'ufficient to allow the bolts to be inserted and tightened. Concrete pipe joints. Joint holes for this type of pipe must be large enough to allow for bells or couplings and for making up and mortaring the joint. Plastic pipe joints. Bell and spigot type of plastic pipe, with O-ring gasket, requires no extra working width in the trench but does require a slightly deeper excavation at the joint locations to accept the bell. Steel and wrought iron pipe. Pipe that is joined by weld ing requires no extra width or extra trench depth at the joints if the welding is done outside of the trench. Joints Types of available joints are discussed in some detail in Part 2, Section 2 under each type of material. The listing in Table 38 brings this information together for convenience. Where a metal line must be maintained as an electrical conductor for cathodic protection, or where the pipe may need electrical thawing, some special provision must be made in jointed pipe installations. For example, in cast iron, lead-tipped rubber gaskets are used on mechanical joints, and conductor wedges are used at the side of the bell on push-on joints. On steel pipe, bonding cables and lugs are CTD000122 MAY 1967 | M 37 TAKE SI--PIPE JOINTS AND THEIR APPLICATIONS Pip material Asbestos-cement Cast iron Typa of joint Application Coupling with rubber ring gasket Push-on Mechanical Bell and spigot Flanged All locations General use Soft soils where set tlement is antici pated, or where flexibility is required Only in stable soil where settlement is not excessive Where valves or fit tings are to be at tached in vaults or above grade Concrete Plastics Steel Wood Wrought iron Flexible ball River crossings Galvanized steel-ring, All locations bell and spigot types or their variations, with rubber gaskets and cement fills Solvent weld In small lines Couplings In small lines Bell and spigot with In large sizes rubber O-ring Mechanical-type couplings Pipes <24 in. ID especially with coal tar linings Welded joints Flanged joints Pipes >24 in. ID with inside coatings Where valves or fit tings are to be at tached Expansion joints (stuffing box type) At points to relieve strain on welded joints Woodstave collars On machine-made pipe Welded All locations up pipe joints depends on the type of pipe material and type of joint. Asbestos-cement pipe. This type of pipe is joined by a coupling with rubber ring gaskets that permit easy assembly and provide a tight seal (Fig. 7). The surfaces of the gasket are tapered to facilitate assembly of the joint. Standards for installing this type of joint appear in AWWA C603-647.29 To make up the joint, place rubber gaskets inside the cou pling as directed by manufacturer's instructions; clean and lubricate pipe ends; place coupling on installed length; align pipe ends; insert last length into coupling, and push on free end until the joint is seated properly. Some pipe (pre belled) is furnished with a coupling already present on one end of each length. "Pushing the pipe home" is accomplished by pressure from a crowbar against a block of wood across the free end of the pipe (Fig. IS). For large pipes, a mechanical puller device may be used. Details on the use of the puller may be obtained from the pipe manufacturer. used at rubber-gasketed expansion joints. Welded joints do not require special provisions for electrical conductance. Packing for bell and spigot joints on cast iron pipe may be calked lead or special rubber gaskets in push-on joints. Rub ber gaskets (O-ring) are also used for asbestos-cement, con crete, some plastic pipe, and steel pipe expansion joints. Laying pipe A number of general directions for laying pipe apply to all types of pipe. The more important ones follow: 1. Before pipe is lowered into the trench, it should be in spected for damage and any unsatisfactory lengths rejected for use. The inside of each pipe length should be swabbed to remove loose dirt and other foreign matter. 2. If mud and surface water have been permitted to stand or flow through strung-out pipe, the inside should be swabbed with strong hypochlorite solution. All gaskets should be kept clean and dry. 3. Pipe should never be pushed off the bank or allowed to fall into the trench. Pipe up to 12-in. in diameter may be lowered by two ropes, one at each end; larger pipe must be handled by machinery. 4. Pipe that is joined by couplings may be laid in either direction, but belled-end pipe is normally laid with the bells facing in the direction in which the work progresses, except downhill, where the direction is reversed. 5. When pipelaying is not in progress, the open ends of installed pipe should be closed by appropriate means to pre vent the entrance of dirt and trench water. 6. Pipe lengths should never be deflected in the joint to any greater degree than recommended by the manufacturer. Jointing procedures. The particular method for making M 38 | WATER AND WASTES ENGINEERING Cast iron pipe. The procedures for making up joints on cast iron pipelines vary with the type of joint used. Bell and spigot joint. This joint generally uses a yarn and lead calking. As each length of pipe is placed in the trench, the spigot end of the pipe is centered in the bell and forced home. The pipe is forced home with a crowbar or mechani cal jack. The procedure for making, up the joint has five steps.80 Step I: Bring the pipe length to correct line and grade and secure it in that position by soil tamped under the pipe, except at the bells. Step 2: Place yam (preferably braided) around the spig ot end and push it into the bell as far as it will go. The yarn should overlap at its ends when around the pipe. Step 3: Place a heat resistant runner around the spigot end and push it tightly against the bell face; add a pouring gate of clay at the top of the pipe. Step 4: Pour melted lead into the pouring gate. On smaller diameter pipes, the entire pour should be from one ladle; if more than one ladle of lead is required, the interval between pourings should be as short as possible. On extremely large pipes, pouring may be done in halves. The depth of the lead joint should be at least 2*4 in. for pipes under 20-in. diam., Vh in. for pipes 20 to 36 in.; and 3 in. for pipe diameters greater than 36 in. Step 5: After the lead has solidified and cooled to the temperature of the pipe, compact (calk) it with either pneumatic or hand calking tools until the finished joint shows a hard and even hammered surface overall. Cement joints may be used in place of lead, in a propor tion of 1 quart of cement to 'A pint of water. The cement is placed inside the bell and thoroughly compacted. When CTD000123 Steel pipeline installed on concrete piers above ground. using this type of joint, six or eight pipe lengths are usually left uncovered behind the length being installed. Mechanical joints. This type of joint consists of four parts: a flange cast as an integral part of the bell of the pipe, a rubber gasket 31 that fits a recess in the socket, a gland (follower ring) to compress the gasket, and nuts and bolts to tighten the joint. The installation steps are four in number. Step 1: Clean the pipe ends, and paint with a soap solu tion. Step 2: Place gland on spigot end with the face toward the bell; then place rubber gasket over the spigot end, with the thick edge facing the follower gland. Step 3: Push the pipe forward to seat the spigot, and press the follower gland into place within the bell. Step 4: Insert bolts in flange and follower gland; screw on nuts thumb tight; then tighten nuts at opposite positions using a torque wrench until all are tightened equally. Push-on joints. This type of joint consists of a special bell cast integrally with the pipe and a special rubber gasket31 designed to fit into a groove inside the bell. The spigot end of the pipe is beveled. The joint is put together in three steps. Step 1: After the inside of the bell and the outside of the spigot are cleaned, the circular rubber is flexed and inserted into the gasket recess in the bell socket. Step 2: A thin film of gasket lubricant (supplied by the manufacturer) is applied either to the inside of the gasket or to the beveled spigot end of the pipe, or to both. Step 3: The spigot end is entered into the bell, using some care to keep it from coming into contact with any soil, and the joint is completed by forcing the plain (spigot) end to the bottom of the bell, using a forked tool, or jack-type tool. Complete detailed instructions are furnished by the pipe manufacturer. Underwater joints. Where the installation is to be in shal low water and only small joint deflections are required, standard mechanical joint pipe is generally used. Where the ' water is deep and the contour of the river bed requires con siderable joint deflection, a ball and socket type of joint is used. Deflections up to 15 degrees are possible. The pipe is generally laid in a trench cut in the bottom of the stream bed. The pipe lengths may be joined on shore and the pipe pulled into the water, using buoyant barrels at tached to keep the pipe off the bottom until the crossing is complete. Sometimes several lengths are assembled on land then floated to the desired location, lowered to the bottom, and joined by divers. Submarine pipelines are usually laid with joints that are provided with positive locking devices to prevent the pipe from being pulled apart. This type of pipe may also be assembled on a barge and lowered from the rear end of the barge to the bottom as the work progresses. Concrete pipe. Concrete pipe may be of a bell and spigot or a steel joint type; both use rubber gaskets. Concrete pipe is frequently lowered into the trench by cable sling attached to the backhoe, or by cable attached to a mobile crane. There are four steps involved in making concrete pipe joints. Step 1: After the ends of the pipe are thoroughly cleaned inside and out, the pipe length is lowered halfway into the trench, and both the spigot and bell ends are lubricated thoroughly with a vegetable soap. Where steel joints are used, they too are thoroughly cleaned with rags, a wire brush, emery cloth, or file as may be necessary, then lubri cated thoroughly with a compound furnished by the manu facturer. Step 2: When the pipe is lowered halfway into the ditch, the rubber gasket is immersed in the lubricating compound, then stretched around the spigot end, and pushed into the groove designed to receive it. Next the gasket is completely covered with lubricant. Step 3: The pipe is then lowered to position, the spigot in serted into the bell and pushed home. In the case of concrete pipe joints, the pipe is not pushed home until a feeler gage has indicated that the gasket is properly placed around the pipe. In large pipe, this "feeler gage" operation is done by a man inside the pipe; on pipe less than 20 in., the "feeler gage" operation is from outside the pipe. The choice of method for "pushing the pipe home" de pends on various factors: size of pipe, location, equipment available, etc. The operation may be accomplished by manipulating the backhoe supporting the pipe by attached cable, or by crane with pulleys. In the latter case, there are three methods rec ommended for making the actual jointing. One consists of using a deadman three lengths back, with a cable connected through a 3-ton pull lift to a strong-back across the bell of the pipe. The second utilizes a winch anchored in a joint re cess three lengths back, connected by cable to a strong-back across the bell. The third method utilizes a cable choker sling around the last pipe installed, attached by ratchet hoist to the laying sling of the pipe length being installed. Exert ing the necessary tension in any of these methods will pull the pipe into final position. Step 4: The joint is completed with a dry mix cement (1:2) inside wetted up for the outside. (Pipe lines smaller than 20-in. diam. do not require an inside mortaring as the exposed metal on these sizes has received an extra heavy zinc coating.) On large pipe sizes, the inside joint is packed with mortar and troweled smooth. Outside joints on steel-type joints are covered with a cloth (or burlap) diaper held tightly in place by wire (or straps). Grout is poured to fill the joint on both sides of the pipe. A stiffer mix is troweled over the top of the pipe. Joints are left uncovered for several lengths back to allow for setting before backfill operations begin. Plastic pipe. This type of pipe, being flexible or some what flexible, is usually joined outside the trench and low ered into the trench as the work progresses, except in the larger sizes where bell-and-spigot type joints are used. Bell and spigot joints. This type of joint requires a three- step operation. Step 1: Clean the bell and plain end and set the gasket ring in its depression in the bell, with the marked edge fac ing toward the end of the bell. Step 2: Lubricate the plain end of the pipe. Step 3: Push pipe end into the bell so the the reference mark on the pipe is in line with the face of the bell or is just within the bell. Other joint types. In Part 2,-Section 4, under the discus sion of manufacture of plastic materials, the methods of jointing are discussed with reference to insert fittings, to flaring and compression joints for polyethylene pipe, and to solvent weld and coupling methods for PVC pipe. CTD000124 MAY 1967 | M 39 Steel and wrought iron pipe. This type of pipe is welded in the trench. Standards for equipment, welding procedures, operators joint design (butt or lap), design and procedure details, testing, etc., have been published by the American Water Works Association.''2 Anchoring. In most pipe lines, particularly those with joints, all dead end fittings, along with bends, tees, and hy drants must be anchored to prevent movement caused by in ternal pressure. Various methods are used depending on the pipe material. This subject will be covered in Manual of Practice No. 4/Valves, Hydrants, and Fittings. Fittings. Crosses, tees, ells, hydrants, and valves are in stalled as the pipeline is laid. Usually, they utilize joints such as have been discussed above. The subject of fittings will be covered in Manual of Practice No. 4. Pipe under railroads. Whenever pipelines are installed under railroad tracks, it is essential that the installation be such that the pipe is protected against superimposed extra dead and impact loads. One of the most general methods used is to install a culvert pipe capable of withstanding the load and to pull the water main through this culvert by wire cable. The culvert should be at least 6 in. larger in diameter than the outside diameter of the pipe bells or couplings. Joints that provide some degree of flexibility are preferred. The space between the pipe and the culvert should not be filled. Some types of pipe may be designed to be jacked di rectly under the tracks. Pipe laid under highways does not require the culvert treatment. Deflection. Many joints have an inherent ability to be de flected to some small degree, a characteristic that permits pipe to be laid on a long-radius curve. The permissible off set and deflection for different types of joints and different pipe materials are given in Tables 35, 36, and 37. Testing All pipelines, of whatever material, should be subjected to hydrostatic test, either by sections as completed or in toio after completion. Such testing is usually done after the trench has been partially backfilled.28-20 Asbestos-cement pipe. In asbestos-cement pipelines, teakage and pressure tests are usually made at the same time over a period of at least 1 hr. After the pipeline is com pleted, it is filled with water, allowed to stand 24 hr, and then subjected to hydrostatic test. The test pressure is usually 1.5 times the operating pressure, and the test is made on sec tions before the backfilling is completed. Allowable leakage is set by AWWA standard;29 it ranges from 0.71 gph per 100 couplings on 4-in. pipe at 50 psi pressure to 13.5 gph per 100 couplings on 36-in. pipe at 225 psi pressure. The data in AWWA C603-64T29 are based on a standard pres sure of 150 psi and a leakage of 30 gpd per mile of pipe per inch of pipe diameter for 13-ft pipe lengths. Cast iron pipe. The usual procedure for testing cast iron pipe is to fill each valve section of the pipeline slowly until all air is expelled, usually through corporation cocks. Then the pressure is brought up to the rest level to determine if any leakage exists at joints. When joints do show evidence of leakage, they should be recalked, otherwise adjusted, or repaired as the joint-type may require. Following observations for leaking joints, cracked pipe, etc., and when the necessary repairs have been made, a leakage test is made over a 2-hr period at the required pres sure. In reference to cast iron pipe lines, leakage is defined30 as the quantity of water that must be supplied into newly laid pipe (or any valved section) to maintain the specified leakage-test pressure in the pipeline after all air is expelled. For cast iron pipe lines, the allowable leakage is limited by two formulas: For mechanical and push-on joints: = ND\/P ~ 3700 Eq. 20A M 40 | WATER AND WASTES ENGINEERING and for calked bell and spigot joints: = ND-y/P 1850 Eq. 20B where L = allowable leakage (gph) N = number of joints in section tested D = nominal pipe diameter (in.) P = average test pressure (psi) These formulas29 are based on an allowable leakage in mechanical and push-on joints of 23.3 gpd per mile of pipe per inch diameter for 18-ft pipe lengths at a pressure of 150 psi, or a leakage of twice that amount for bell and spigot pipe of the same length under the same conditions. Other pipe materials. Standard procedures for testing pipelines of materials other than asbestos-cement or cast iron have not yet been issued by the American Water Works Association, but it is good practice to test all pipelines for leakage regardless of pipeline material and to make certain that leakage is within acceptable limits. Backfilling Regardless of the type of pipe material, the proper han dling of backfilling operations is important and deserves more than casual attention. Common practice involves a two-step procedure: partial backfill before leakage tests and completed backfill after tests. The partial backfill procedure usually leaves joints ex posed or covered only by a relatively shallow layer. Whatever the pipe material or the method of backfill, the backfill material should be good soil which does not contain any rocks, bad soil, or frozen clods. The following directions are abstracted from AWWA standards.29-30 Asbestos-cement pipe. Backfill material is deposited at both sides of the trench uniformly and for full trench width up to the horizontal centerline of the pipe. It is then tamped in layers 4-in. thick after compaction. The backfill material should contain sufficient moisture to permit thorough com paction under and on each side of the pipe to provide voidfree support for the pipe. Where visual inspection during leakage tests is not re quired, backfill is added to the depth indicated above and then a cushion of hand-placed material is added to cover the pipe to a depth of 12 in. for all pipe sizes. When visual inlspection is required and joints are lqft exposed during leak age tests, hand-placed material is deposited to a depth of 12 in. over pipe 8-in. in diameter or less, and to a depth of 24 in. over larger pipe. After leakage tests are completed, exposed couplings are covered with hand-placed material to a depth of 12 in. The remainder of the backfill material (no more than 25 percent stones, all less than 6-in. in diameter) is deposited in the trench by hand or by bulldozer. If trenches are in a roadway right-of-way, the backfill is compacted to a 90 percent compaction density. Backfill in other trenches need not be tamped. Cast-iron pipe lines. Selected backfill (i.e., sand, gravel, crushed rock, or limestone) is used only to a depth of 1 ft above the pipe, in situations requiring such material (see Bedding). Backfilling under pipe, bells, valves, fittings, and appur tenances is done by hand from the trench bottom to the hor izontal centerline of the pipe, with the fill being placed in 3-in. layers and compacted by tamping. Backfilling material is deposited in the trench to its full width on each side of the pipe. Backfilling above the pipe centerline to a depth of 1 ft above the pipe is placed by hand or by approved mechanical methods to avoid either injury to or movement of the pipe. The type of backfill material must be suitable for local con ditions. CTD000125 From the point 1 ft above the pipe to the surface grade, the trench is backfilled either by hand or approved mechan ical means, with backfill material suitable to the local condi tions; usually this is excavated material, except in cases of rock or bad soil. AWWA standards30 specify details for backfilling under pavement, where settlement is important, backfilling in freezing weather, and type of selected backfill materials. Also covered are matters of removal, restoration, and main tenance of pavement surfaces, as well as cleanup after back filling operations. Concrete pipe. Only good soil or selected backfill mate rial should be used. It is generally placed in 6- to 8-in. layers and tamped with curved tampers (Fig. 19) so that the fill is firmly compacted around the pipe to the springline. From this point to a depth of 12 in. above the pipe, the backfill is shovel tamped. Above this point, the backfill material is placed in the trench by bulldozer or other mechanical equipment. Fig. 19. Haunch hand tamping device for backfilling opera tions. Other pipe materials. Similar backfilling and compaction operations are used for other types of pipe. In the case of plastic materials, the selection and placement of backfill material should be made with due consideration to the pos sible effect on the pipe. Disinfection Observations throughout the country have indicated that no single procedure for new main disinfection has been uni versally satisfactory. The procedure presented in brief here is based on the one set forth in AWWA Standard C601-54,34 as it was adapted in BIF Industries Keep Sheet 12A.35 Contamination sources. Water pipe lying on the ground before installation is subject to contamination, and there is also a strong possibility of contamination while the line is being made up. Undesirable bacteria may be in the trench soil, and contaminated trench water may find its way into the open end of a pipe. In pipelaying, the interior of pipes should be kept free from foreign matter and swabbed with an effective bacteri cide; open ends should be blocked to prevent trench water from entering pipe. Joint packing materials (in order of preference) are; solid molded or tubular rubber rings, asbestos rope, treated paper rope, and braided cotton. Preliminary flushing. Flushing a main prior to disinfec tion is desirable to remove foreign material from new or re paired mains. Flushing should be done after the pressure test at a minimum flushing velocity of 2.5 fps. Actual prac tice has shown that a velocity of approximately 3 fps is re quired for scouring. The chart in BIF Industries Keep Sheet 12A35 reveals the volume of water (in gallons per linear foot) required to fill various pipe sizes. From these values, the bleed rate to obtain a flushing velocity of 3 fps can be determined. For example, for a 24-in. main, each foot of length contains 23.5 gal. For a minimum velocity of 3 fps, the flow must be at least 23.5 X 3 = 70.5 gps or 42.30 gpm. Disinfectant. The following disinfectants may be used on pipe: chlorine or chlorine water; calcium hypochlorite (HTH, Perchloron, Pittchlor, etc.); sodium hypochlorite solution; or chlorinated lime-water mixture. Application point. Chlorine should be applied at one ex tremity of a pipe section and bled at the opposite extremity of a properly segregated section. Precautions must be taken to prevent dosed water from flowing into the potable water supply. Chemicals are injected through corporation cock or capcock inserted in line for that purpose. All high points on section treated should be properly vented for air escape. Chlorine dose. The chlorine requirement depends on the degree of contamination, type of packing used, and pH of water. These factors must be all considered in deciding on the dose. The rate of application should give a uniform dose of at least 25 mg per L at the end of section being treated. Higher chlorine dosages may be required. Contact period. The average disinfecting period should be 24 hr and should produce no less than 10 mg per L at the end of the line after the retention period. If unfavorable or unsanitary conditions of installation, poor packing, or high pH exist, the period may need to be extended to 48 or 72 hr. If shorter retention periods must be used, the chlorine concentration must be increased to 50 or 100 mg per L. Experience dictates requirements. The rate of final removal of chlorinated water is not im portant, but the line should be bled until the chlorine residu al approaches that normally carried. The efficiency of disin fection should be checked by bacteriological tests wherever possible. Calculations involved. Uniform application of the disin fecting solution involves the calculation of the capacity of the pipeline, using the pipe size and length of line to be sterilized. The amount of hypochlorite required is deter mined from the selected chlorine dosage, the available chlo rine content of the hypochlorite solution, and the bleed rate. It rs necessary to know the duration of the bleed-off period so that the chlorine dosage may be carried to the extremity of the line. To accpmplish constant bleed rate, an open nozzle dis charge (calculated from formulas) may be used, or a Rate Setter, with flow reading in gpm, may be attached to a hydrant. The chart in Keep Sheet 12A is useful in making all of these calculations. An example on the chart shows steps for its use. Equipment. Three factors govern the selection of equip ment for main disinfection: the line pressure involved; the amount of chlorine compound to be fed; and the method of operating the feeding unit. These factors are considered in some detail in BIF Keep Sheet 12A.33 Repetition of procedure. If this procedure does not effect a thorough disinfection of the line, the operation should be repeated, or a residual chlorine content of 0.4 mg per L should be maintained in the main for a period of 20 to 30 days after it is put into operation. CTD000126 MAY 1967 | M 41 Tunneling mole for service line installation. Section 2--Service Lines Components of a customer's service line include a con nection to the main (corporation cock), curb cock or turn off valve, and the line itself. The installation of service lines is usually done during the early construction period of the structure to be served. Gen erally, the service tap to the main is made at the same time, although some utilities have installed corporation cocks when the mains are laid (see discussion in Part 1, Section 3). Determination of the size of the service (Part 1, Section 3) and selection of the materials (Part 2, Section 8) pre cede the installation operations. These operations consist of trenching, main tapping, laying the line, installing the valves, and backfilling. Equipment Every utility should have one or more trucks equipped with tools and materials for making service line installa tions. The truck should contain all necessary tools for trenching and installing the line and its appurtenances, as well as safety barricades and emergency items. In addition, it should contain service line pipe and appurtenances. The number of trucks needed depends on the size of the utility and the number of installations to be made in a normal work day. The size of the work crew will depend on the number of installations to be made and the extent of the work involved. This latter factor depends on whether or not the utility installs the line only to the property line or curb box and valve or to the premises. The number of men needed for an installing crew de pends on the extent of the work involved in each installa tion, but the minimum number should include a foreman, one skilled workmen for making the taps, plus unskilled la borers as needed. Some utilities maintain a separate truck and crew for installing services larger than 3 in. Trenching The depth at which service lines are laid is important. If too deep, the installation is too expensive; if too shallow, the line will be subject to freezing in cold climate areas. The trench may be dug by hand or by small backhoe. When dug by hand, the width must be sufficient to accom modate the digger. Trenches dug by backhoe may be nar rower, except at the location of the curb box and tap. At these points, the excavated area must be sufficiently large to permit workmen to carry out the task of making up the nec essary connections. The trench bottom should be relatively flat and on the grade necessary. Special bedding is not required unless the soil is corrosive in nature and the pipe is not corrosion re sistant. Where the service line connection must be made under a pavement, it is necessary to remove the pavement and re place it after the installation is completed. Tunneling for installing service lines is possible with a pneumatic underground piercing tool. The missile-shaped device is 45 in. long and has a bit in the nose; it is powered by compressed air. It will pierce holes up to 5% in. diam. for distances up to 100 ft. In operation, the device is moved through the soil by rapid hammer blows from an internal piston operating against the bit. The forward movement of the tool may be as much as 4 fpm in sandy soils, or as little as 1 in. per min in hard cemented soils. The use of this de vice requires only two holes to be dug, one at each end of the line, each hole large enough for a workman to operate the tool. If the service line to be installed is of flexible material, the flexible service line itself may be used to carry air to the tool. As the tool moves forward, it pulls the service line with it, and when the hole is complete, the line is already in place. Shale and small stones do not alter the line of move ment of the tool, but large rocks will deflect or stop it, requiring that an opening be dug at that point and the tool redirected on its course. Tapping Methods for making service line connections to mains vary depending on the service line size and material and the main size and material. Where the size and the wall thick ness of the main are sufficient to provide adequate full threads for the corporation cock, service lines of % in. are connected to the main by direct drilling, tapping, and inser tion of the corporation cock into the main. If the main is under pressure, the tapping, drilling, and insertion operation is done with a special tapping device. This operation is known as a wet tap. In multiple tappings for a single line, the taps should be spaced 10 in. apart and staggered around the pipe to avoid weakening it. Most utilities usually install single taps at a point 45 degrees above the horizontal center line of the pipe and on the side of the main nearest the premises to be served. Some utilities, however, install taps on top of or at the side of the pipe, and some at 22VS degrees above hori zontal. If the pipe wall is too thin for direct tapping or will not provide the required number of full threads, service clamps are used. In such cases, drilling is done through a corpora tion cock that has been screwed into the service clamp. M 42 | WATER AND WASTES ENGINEERING CTD000127 Tees, wyes, or special branch connections are used for connecting larger service lines, and larger drilling machines are used to drill through tapping sleeves and valves for mak ing lateral or branch connections to mains in service. This whole subject of valves, fittings, and their installa tion will be covered in detail in Manual of Practice No. 4 on valves, hydrants, and fittings. Laying and backfilling Installing the pipe involves not only the laying of the pipe line, but the installation and connection of the curb cock and valve box at the property line, and the connection of the line to the corporation cock and sometimes to the shut off valve or meter at the premises. Where outside meters are set, the operation is frequently done as a part of the service line installation operation. When the service line material is not flexible, a flexible gooseneck connection is made from the corporation cock to the curb shutoff valve, and, if necessary, from the line to the house shutoff valve or meter. The flexible gooseneck may be of lead, copper, or plastic. The line itself should be laid on the trench bottom or snaked through the tunnel, as the case may be, with con sideration given to prevention of kinds or bends. When the final connections are made, the installation should be tested under pressure. Backfilling of trenches may be done by hand or by ma chine. In either case, large stones or boulders should not be placed directly on the line. Backfilling without tamping is usually done to some reasonable level above grade to allow for settlement. Backfill in areas to be paved should be tamped to at least 90 percent of the compaction value of surrounding areas, then allowed to stand with temporary pavement for at least 3 months before permanent pavement is replaced. Restrictions on and specifications for excavat ing, backfilling, and resurfacing paved areas are usually set forth explicitly by the utility or in contracts a utility may make with an independent contractor. Section 3--Inplant Systems Inplant piping systems are usually installed by the con tractor during the construction of the facility, but additions to or revisions of installed lines may be done by utility personnel. As indicated earlier, most large cast iron lines in plants utilize flange-type joints. Steel and wrought iron lines may be welded, or flange joints may be used where connections are made to equipment that is removable for maintenance and repair. Asbestos-cement pipelines utilize regular cou plings or special fittings. Concrete pipelines are assembled in the same manner as in the field, except where connections are made to pumps, for example. Small pipelines are usually joined by couplings or unions where the pipe has to be broken for removal or for removal of attached equipment. Plastic pipe is joined in the same manner as previously described. Rubber hose is connected through inside fittings, and glass through special joints. Pipelines that* are small or do not have sufficient rigidity to support themselves over the span of their length must be supported by hangers from above or below, by concrete blocks or pillars, or by metal pipe supports. Pipelines installed in plant facilities should be painted and color-coded at the time of installation (see Part 1, Section 4). jwater and wastes engineering MANUAL OF PRACTICE NUMBER TWO WATER SYSTEMS pipes and piping Maintenance and repair procedures on pipelines are per formed only when necessary to prolong the life of the line and to maintain its carrying capacity. In essence, this means to prevent or remedy deterioration effects on both the out side and inside of the pipe and to repair structural failure or leaks in the pipe system. Deterioration effects result from the corrosive or erosive action of water inside and of soil moisture outside. Hie cause and nature of this corrosive action is a subject for a future Manual of Practice in this series and therefore will not be discussed here. It is sufficient, for the purpose of this manual, to recog nize that metals, concrete, and asbestos-cement all may be subjected to deleterious conditions, both inside and outside, and that, under some circumstances, these conditions may adversely affect the life and carrying capacity of the pipe. Pipelines constructed from any of these materials also may be subject to failure or leaks, under some circumstances, es pecially if the line has not been laid properly, or if joints are improperly made. If a pipe should deteriorate or if the line should leak or fail, maintenance procedures are in order. Various techniques to prevent corrosion and its adverse effects are used in modern pipe manufacture. These meth ods include coating and lining the pipe, curing, etc. These various methods have been discussed in some detail in the PART. 4/ MAINTENANCE sections dealing with pipe manufacture in Part 2. The performance of a transmission or distribution system depends on the ability of the pipe to resist unfavorable con ditions and to operate at or near the capacity and efficiency that existed when the pipe was laid. This performance is checked in several ways: measurement of flow, fire flow tests, loss of head tests, pressure tests, simultaneous flow and pressure tests, and tests for leakage. These tests are car ried out as a part of operation, and therefore, the details of the methods will be covered in a Manual of Practice on the distribution system. However, the results of some of these tests, particularly those related to leakage losses and loss of carrying capacity, are important to maintenance operations and will be covered here. In general, the subject of maintenance as presented here is limited to a discussion of leakage, loss of carrying capac ity, pipeline cleaning, lining mains in place, main break re pair, cathodic protection, service line cleaning, and thawing of frozen pipelines. Maintenance of inplant piping systems is usually confined to external painting or the renewal of color-coding. Inplant line cleaning or repair, when neces sary, generally can be done by the same methods as dis cussed in the following sections. The cutting of pipe and the insertion or installation of valves, hydrants, or branches will be covered in Manual of Practice No. 4/Valves, Hydrants, and Fittings. CTD000128 MAY 1967 | M 43 Section 1--Pipeline Leakage Distribution mains and transmission lines are generally buried, and it is therefore not possible to carry out a com prehensive and systematic checking on any routine basis. One way to minimize incipient failures or deficiencies is to keep records of leakage and breakage observations; another way is to make pressure, flow, and pipe coefficient surveys on a more or less regular basis. A third approach is to have the employees in the field (installation and distribution crews, meter readers, and servicemen) note and report any unusual conditions related to pipe failure or leaks. Whenever the amount of water pumped into a system is more than the quantity sold, as indicated by customers' me ters, or by main line metering, then there is either leakage on the system or incorrect registration by the meters. Gen erally, nonrevenue or unaccounted-for water is a result of both factors. Meter repair and maintenance are not a part of piping system maintenance, but pipeline repair is. Leak surveys Leak surveys are essential to the location of wasted water. The importance of finding leaks is greater where main pressures are high because a system pressure of 100 psi results in more leakage than a pressure of 50 psi. Pitometer surveys. The most effective method of locating leaks in a distribution system is a survey utilizing pitometer measurements to determine flows. These surveys are usually made at night, at times of minimum flow, with observations being made in sequential areas. Usually, most of the valves in the area are closed so that the water entering the area will come from one line only. A pitometer is inserted into this line, and the flow determined. If the flow is greater than should be expected for that area at that time of day, the area is divided into sub-areas, and pitometer flow meas urements are made in each. In this manner, the location of the leak is narrowed to a small area. Once the area of the leak is determined, the location of the actual leak is necessary before repairs can be made. Finding the leak itself may involve a number of different approaches, including the following: house to house inspec tion, observation of ground surface for wet spots, observa M 44 | WATER AND WASTES ENGINEERING tion of sewer flows in the vicinity, sounding rods, study of the hydraulic grade line by pressure tests along the line, lis tening for sounds of running water by means of electronic sound amplification or sonoscope (aquaphone, geophone, or detectophone). Leak repair Having located the leak, the next step is to uncover the pipe and make the necessary repairs. Maintenance crews for this work need a truck and such tools, instruments, and communication and repair equipment as may be necessary to make the excavation and perform the repair operation. It is frequently necessary to utilize a dewatering pump to make it possible to work around the pipe. Repair equipment and material used will depend on the type of leak. For example, joint leaks in calked bell and spigot joints can be recalked. Sometimes lead yarn is used. Sometimes new gaskets are driven into joints. In some cases, it may be necessary to shut off the line, remove the joint, and replace it. The type of pipe and joint will dictate the re pair method. If the pipe is cracked or has failed for any of the possible causes, it is usually necessary to shut off the line and re move the damaged section. A whole length may be removed and replaced, or the damaged section of a single pipe length may be cut out and replaced by an insert. Various types of tools and saws for cutting through the pipe are available. The design and operation of these cutting devices depend on the material to be cut. Whether a whole pipe length or a short section is re placed, the operation should be performed with as much care as is used in installing new pipelines, and the equip ment and materials used should be made for that specific purpose. Splits or cracks in pipe or leaks through the pipe wall caused by corrosive pitting may also be repaired by cutting out the affected section, or they may be more simply re paired by the use of special repair sleeves. These sleeves come in various sizes and lengths and are simply placed around the pipe and tightened to produce an effective repair. Leaks around valve stems are repaired by repacking the stem. Broken or damaged corporation cocks and service lines are replaced. After the repair is made, the excavated hole is backfilled. Backfilling operations should receive the same attention as in installation of new pipelines. When paving has been cut, the process of repaving should be the same as used after in stalling new pipelines. Before the repaired pipeline is placed back in service, it should be disinfected, using the same procedure as for disin fecting new lines. It is not usually necessary, however, to maintain any extra chlorine residual in the line after the disinfecting water has been bled off. Value of leak repair. The effectiveness of such leak sur veys and repairs is exemplified by this tabulation of results found in a large Midwestern city. Location Service Abandoned service Main Hydrant Valve packing Meter Number of teaks 146 14 32 22 6 43 Leakage(gpd) 1,728,000 830,000 2.502,000 248.000 67,000 154,000 is not economically feasible to locate and repair all leaks. A rule of thumb regarding leak surveying of any area is that there is little likelihood of water waste when the night consumption rate of an area is less than 50 percent of its av erage daily use. In the city cited above, nonrevenue water was reduced from 19.6 to 8.3 percent. That city also established the CTD000129 value of 3000 gpd per mile of main as the level below which it costs more to locate and repair the leak than to allow it to exist. Another value for this minimum has been stated as 250 gpd per inch diameter per mile of pipe. On this basis, the above minimum value of 3000 gpd would be for an av erage main size of 12 in. Section 2--Loss of Carrying Capacity Decreases in the carrying capacity of pipelines result from increased friction in the system, caused by roughness of the interior walls of the pipe, or from a decrease in the effective inside diameter of the pipe, or from both factors. Friction increases when the internal surface of the pipe be comes rough because of corrosion, pitting, tuberculation, deposits of sediment, or slime growths. In addition to caus ing rough or uneven surfaces, tuberculation, deposits, and slime growths reduce the internal diameter of the pipe. Tu berculation, that is, the growth of conelike barnacles, is lim ited to unlined metals of ferrous composition, but all other pipeline materials are subject to corrosion (or erosion), pit ting, deposits, and slime growths. Coefficient tests The method used to determine loss of carrying capacity is generally called a flow coefficient test or C-value test. In this test, a section of the distribution system is isolated, and branch lines are shut off, so that no water can be withdrawn by consumers. A pitometer is inserted into each end of the isolated section, and pressure values at each end are re corded over a period of time, either under normal or induced-flow conditions. The difference between the pres sure values at the two locations is a measure of the loss of head. From values for the slope of the pipeline, velocity of flow as indicated by the pitometer readings, and pipe diam eter, the flow coefficient (C-value) is calculated. Any ap preciable drop from the value for the pipe when new or from a previous observation indicates loss of carrying ca pacity and, therefore, a need to remedy the situation. Remedies Means for remedying loss of carrying capacity include operating procedures, or the use of special mechanical pro cedures for improving the internal surface of the pipe. Operating procedures. Methods for improving carrying capacity by operating procedures are characterized as physi cal or chemical. The physical method involves line flushing to remove sediments and sometimes slimes. The chemical methods have one of two purposes: to prevent slimes or to prevent corrosive action. Flushing. Flushing is accomplished simply by opening a fire hydrant at the end of a line or on a line and allowing the water to discharge freely until it runs clear. Greater flows through the line with fewer customer complaints can be achieved if the flushing is done late at night. Higher pumping pressures and/or the shutting-off of branch lines will increase the effectivness of the flushing operation. Un planned main flushing may occur when hydrants are opened for fire-fighting purposes. Chemical treatment. Chemicals may be added at the treatment plant to prevent loss of carrying capacity. The choice of chemical treatment depends on the desired effect. Slime control. When loss of carrying capacity is caused by slime growths in pipelines, the use of chlorine or ammonia-chlorine treatment may be quite effective. The amounts of the chemicals added, point of application, and residual control are all matters of operation and relate to the particular situation and local conditions. Control of aggressive water. Another operating treatment is the control of the aggressive characteristic of the water, either by pH control or by the maintenance of a positive calcium carbonate index. The addition of a hydroxide com pound to react with carbon dioxide will increase the pH to a level that is not deleterious to pipe materials. Passage of highly carbonated water over limestone beds is also effec tive. The maintenance of a small excess of colloidal calcium carbonate will provide for a deposition of calcium carbon ate on the interior surface of the pipe and protect against attack. Glassy phosphates. The addition of sodium hexameta- phosphate or sodium-zinc hexametaphosphates in small quantities is an effective means for combatting "red water," which is caused by attack on ferrous metal pipes. The amounts used (dosages of 2 to 4 mg per L), the point of ap plication, control, etc., are all matters of operation. Section 3--Cleaning and Lining The process of removing corrosion deposits and slimes from the inside of pipelines by mechanical means is known simply as cleaning. The process of placing a protective coating on the inside of a pipeline that has been cleaned is termed lining, or lining-in-place. Cleaning Three basic techniques are used for in-place pipeline cleaning; these are drag, hydraulic, and mechanical. The choice of method depends on these factors: pipe diameter, water volume and pressure available, length of pipe to be cleaned, amount of encrustation or sediment, ease of access, distance between access points, provisions for disposal of wastewater from cleaning operations, and other local condi tions. Cleaning without lining is effective, but there can be no assurance that the pipe's carrying capacity will remain at its improved level for very long because cleaning does not re move the causes of pipeline deterioration. Cleaning alone is an expensive means of maintaining carrying capacity. Drag cleaning. This method of cleaning is usually limited to pipe diameters of 4 to 24 in. The cleaning equipment is pulled through an out-of-service line by a power winch. Normal service may be maintained by a temporary bypass line. Scraper tool for main cleaning. Drag cleaning utilizes a spring-steel cleaning tool that is composed of a series of scrapers, followed by an assembly of tight-fitting squeegees. As the tool moves through the line, accumulated deposits are loosened by the scrapers, and then mechanically removed by the squeegees. The separate drag operations are repeated until the pipe wall is clean. Access openings are made in the pipeline at intervals of 300 to 500 ft, depending on pipe size, line configuration, and condition of pipe. Hydraulic cleaning. This method of cleaning is most practical in long, comparatively straight runs of transmis sion or arterial mains. The method requires an adequate supply of water at a given pressure. The volume of water available and the required pressure depend on pipe size. The greater the volume of water available the lower the pressure required. The tool used in the hydraulic cleaning process consists of spring scrapers so arranged that part of the water push ing the tool is released through it to flush the scrapings and debris ahead of it. The tool usually travels at a rate of 50 CTD000130 MAY 1967 | M 45 it requires less steel, and it conforms to the inside contour of the line. Mandrel process. The mandrel process, commonly called the Tate process after its Australian inventor, is applicable to lines from 4 to 16 in. in diameter containing relatively few service connections or laterals. The process uses a pressurized extrusion technique, which can be described briefly as follows: after cleaning, a tight-fitting baffle is threaded onto a cable in the pipeline; a two-part sand, one-part cement mortar mix is loaded into the pipe against the baffle; and a conically-shaped mandrel is then secured to the cable. The mandrel is composed of centering springs, metering springs, a perforated skirt, and a troweling edge. The assembly is pulled through the pipe, usually for dis tances of 350 to 450 ft. Back-pressure of the baffle forces the mortar over the cone of the mandrel and against the pipe wall. The perforated skirt squeezes out excess moisture, and the troweling edge produces a smooth, dense coating. Because of the pressure created during the lining process, existing side lines must be removed or plugged. Section 4--Cathodic Protection This type of protection against pipe deterioration is not economical or feasible to use for protecting a distribution system, but it may be useful on long transmission lines. The economic considerations that enter into any justifica tion of the use of cathodic protection of pipelines include the following: service life of line, importance of uninter rupted service, costs and hazards of leaks or failures, availa bility of repair crews, comparison of coating methods with cathodic protection, and probable cost of adding protection after construction. There are two cathodic protection sys tems: galvanic (or sacrificial) anode and applied potential. In the galvanic system, use is made of the preferential so lution potential of metals in the electromotive-force series. This system uses no external power but employs magnesi um, zinc, or aluminum anodes. This type of system is par ticularly applicable where the current requirements are small, as in coated pipelines, or where no external source of electrical energy is available. In the applied-potential system, an external source of power is necessary to impress the required potential onto the line. This system uses graphite, carbon, steel, iron, or aluminum anodes. The system also requires power conver tor devices. Pipelines to be protected by cathodic protection must be insulated from all other sections of the system, and they must proride continuous electrical connection from one sec tion to another, as mentioned in Part 3 on installation. The design of cathodic protection systems will be dis cussed in a manual oh corrosion. ' Section 5--Thawing and Cleaning Services Where pipelines or services do not have sufficient cover to prevent freezing, it is often necessary to thaw the lines. This practice is generally confined to service lines, but may be applied to mains of relatively small diameter. There are two methods, electrical and steam thawing. Electrical thawing is only applicable in .metal lines capa ble of carrying an electrical current. Steam thawing is slow and most useful only on metal lines where insulating materi al in the pipe joints makes it impossible for the line to con duct electricity. Thawing services Electrical thawing is quick and relatively inexpensive. It requires a source of current (a d-c generator, such as a welding outfit, or a transformer connected to an a-c outlet) and two insulated wires connecting the current source and the pipe at points that define the frozen section. As current flows through the pipe, heat is generated, and the ice begins to melt at the wall. When the water starts to flow, the rest of the ice is melted by the flowing water. Services are usually thawed with 50 v or less; mains (600 ft maximum length) with 100 v. The detailed procedures, which involve current and volt age control, time, precautions, personnel, etc., are matters of operation rather than maintenance and will be covered in a manual on distribution system management and opera tion. Cleaning services Under some conditions, service lines may become en crusted with calcium carbonate deposits or partially plugged by sediment. Cleaning may be accomplished by dragging or pushing a scraper through the lines. These scrapers consist of cutting knives and brushes on a cable that is twisted as it progresses forward. Power twisting is most effective. Carbonate encrustation may be removed by treatment with inhibited muriatic acid, which also will attack rust but not the pipeline itself. Two percent of aniline oil in a 5 per cent solution of muriatic acid is effective. The line must be thoroughly flushed after cleaning. Service line "shooting" with compressed air may be used to blow out sediment. An air compressor with reservoir tank is attached at the house, and the line is exposed at the cor poration cock or shut off valve so that waste may be dis charged freely to the air. Compressed air under 90 or 100 psi pressure is used to force the water out of the line. The air pressure is released into the line suddenly. When air ex its from the open end of the line, the line is refilled with water and flushed, then the operation repeated until the flushing water flows clean. CTD000131 MAY 1967 I M 47 Author's Note In many places in this manual, it has been stated that cer tain subjects, related to the discussion at hand, were matters of operation that would be covered in subsequent manuals in this series. In a project of this type, limitations of page space available dictate the extent of coverage of any one manual. The reader may disagree with the organization of the material and the selection of material to be included in the several manuals. It is hoped, however, that as future manuals are published, the reasons for the content of each will be apparent, and a maximum overall usefulness of each will be attained. ACKNOWLEDGMENT For the preparation of this manual, ibe author has drawn heavily on both manuals and standards published by the American Watet Works Association, as well as on source material and illustrations supplied by associations of pipe manufacturers and by individual pipe*producing companies. The author is also indebted to a number of individuals for their assistance in reviewing various sections of the manual during its preparation. These reviewers are: j. F. Baker, product manager--water pipe, Pipe Div., JohnsManville Corp. R. E. Bald, chief engineer, Pipe Div., International Pipe and Ceramics Co. Joseph Braslow, market director, Plastic Pipe Institute Palmer Brown; manager--pipe products, Visqueen Div., Ethyl Corp. Gerald D. Cornell, United States Steel Corp. Roger Dittig, manager--technical services, Cast Iron Pipe Research Association. M. H. Ellis, senior market specialist, Armco Steel Co. William Gonsier, chief engineer, Price Brothers Co. Inc. H. S. Goodspeed, senior engineer, Pipe Div., Johns-Manville Corp. Dennis Healy, supervisor--market planning and services, Celanesc Plastics Corp. E. R. Lassone, service manager, Certain-teed Products Corp. G. A. Nielson, senior engineer, Pipe Div., Johns-Manville Corp. A. B. Perrone, senior engineer, Pipe Div., Johns-Manville Corp. E. N. Seward, sales manager, Smith-Scott Co. Joseph Smith, advertising manager, A. M. Byers Co. Additionally, the author is deeply indebted to his staff for exten sive help in the production of this manual, in particular: Priscilla G. Perlman, associate editor; Josette Trenchard, assistant editor; and Eleanor Trenchard, editorial assistant. Many of the illustrations used in this manual were furnished by individual manufacturers or by manufacturer associations. The author's indebtedness to these contributors is hereby acknowledged. REFERENCES 1. Seidel, H. F. and Cleasby, J. L., "A Statistical Analysis of Water Works Data I960," JjiWWA 60, 1507 (1966). 2. Anon., "Standard Schedules for Grading Cities and Towns," New York, American Insurance Assn., 1956, p. 15. 3. Burdick, C. B., Wat. & Sew. Wks. 94: 233 (1944). 4. Anon., "Design Manual, Civil Engineering" NAVDOCKS DM-5, Washington, D. C., Engineering Facilities Command, U. S. Navy, 1962. 5. Adams, D. P., "An Index of Nomograms," New York, John Wiley & Sons, InC., 1950, Ch. 6, p. 112. 6. Anon., "Handbook of Cast Iron Pipe," 4th ed., Chicago, 111., Cast Iron Pipe Research Assn., 1967. 7. Anon., "A Training Course in Water Distribution" (AWWA M8), New York, AWWA, 1962, p. 141. 8. Al'bett, R. W., "American Civil Engineering Practice" Vol. II, New York, John Wiley & Sons, Inc., 1956. 9. Tong, A., O'Connor, T. F., Stearns, D. E., and Lynch, W. O . J.AWWA 53: 192 (1961). 10. Smith, M. C., Wat. A Sew. Wks. 95: R-69 (1948). 11. Anon., "U.S.A. Standard Scheme for the Identification of Piping Systems" (A 13.1), New York, Amer. Standards Assn. (Now U.S.A. Standards Institute), 1956. i 12. Anon., "Standard Practice for the Selection of Asbestos-Cement Water Pipe" (AWWA H-2), New York, AWWA, 1964. 13. Marston, Anson, "The Theory of External Loads on Closed Conduits in Light of Latest Experiments," Iowa State Coll. Eng. Exp. Sta. Bull. No. 96, 1930. 14. Anon, "AWWA Standard for Asbestos-Cement Water Pipe" (AWWA C400-65), New York, AWWA, 1965. 15. Cohn, M. M., "Sewers for Growing America," Ambler, Pa Certain-Teed Products Corp., 1966. 16. Anon., "American Standard for Thickness Design of Cast Iron Pipe" (AWWA H-l), New York, AWWA, 1967. 17. Anon., "American Standard for Thickness Design of Ductile Iron Pipe" (AWWA H-3), New York, AWWA, 1965. 18. Anon., "American Standard for Ductile-Iron Pipe, Centrifugally Cast in Metal Molds or Sand-Lined Molds for Water or Other Liquids." (AWWA 051-65), New York, AWWA, 1965. 19. Anon., "AWWA Standard for Reinforced-Concrete Water Pipe-- Steel Cylinder Type, Not Prestressed" (AWWA C300-64), New York, AWWA. 1964. 20. Anon., "AWWA Standard for Reinforced-Concrete Water Pipe-- StodC^Iinder Type, Prestressed" (AWWA C301-64), New York, M 48 | WATER AND WASTES ENGINEERING 21. Anon., "AWWA Siandaid for Reinforced-Concrete Water Pipe-- Noncylinder Type, Not Prestressed" (AWWA C302-64), New York, AWWA, 1964. 22. Anon., "Steel Pipe Design and Installation" (AWWA Manual Mil), New York. AWWA, 1964 23. Anon., "AWWA Standards for Fabricated Electrically-Welded Steel Water Pipe" (AWWA C201-66), New York, AWWA, 1966. 24. Anon., "AWWA Tentative Standard for Mill-Type Steel Pipe" (AWWA C202-64T), New York, AWWA, 1964. 25. Anon., "Ring Deflection Design for Welded Steel Pipe," River side, Calif., Smith-Scott Co., Inc., 1966. 26. Anon., "AWWA Standard for Coal Tar Enamel Protective Coat ings for Steel Pipe" (AWWA C203-62), New York, AWWA, 1962. 27. Anon., "Tentative AWWA Standard for Cement-Mortar Protec tive Lining and Coating for Steel Water Pipe" (AWWA C205 62T), New York, AWWA, 1962. 28. Anon., "Collected Standards for Service Line Materials" (AWWA C800-55), New York, AWWA, 1955. 29. Anon., "Tentative AWWA Standard for Installation of AsbestosCement Water Pipe" (AWWA C603-64T), New York, AWWA, 1964. 30. Anon., "AWWA Standard for Installation of Cast Iron Water Mains" (AWWA C60Q-64), New York, AWWA, 1964. 31. Anon., "American Standard for Rubber Gasket Joints for Cast Iron Pressure Pipe and Fittings" (AWWA Cltl-64), New York. AWWA 1964 32. Anon., "AWWA Standard for Field Welding of Steel Water Pipe Joints" (C206S2), New York, AWWA, 1962. 33. Anon., "A Guide for Installation of Cast Iron Water Mains," Chicago, 111., Cast Iron Pipe Research Assn. 34. Anon., "AWWA Standard for Disinfecting Water Mains" (C60154), New York, AWWA, 1954. 35. Anon., "Keep Sheet 12A--Water Main Disinfection" Providence. R. I., BIF Div., New York Air Brake Co., 1956. LIST OF TABLES 1. Water utility production by population groups. 2. Rate of flow required in cities of various sizes. 3. Transmission and distribution pipeline materials. 4. AWWA standards for water pipe. 5. Type of residential area vs. fire-flow required. 6. C-values of various pipe materials. 7. Preferred C-values for flow calculation. 8. In-plant piping materials. 9. Relation of bedding conditions, pipe size, and load factors for A-C pipe. 10. Impact factors due to moving vehicles (for A-C pipe). 11. Flexural test loads for A-C pipe. 12. Crushing test loads for A-C pipe. 13. Allowances for water hammer (C.l. pipe). 14. General design requirements for concrete pipe. 15. Design requirements for reinforced concrete pipe--not prestressed. 16. Design requirements for reinforced steel cylinder con crete pipe, prestressed. 17. Design requirements for noncylinder concrete pipe, not prestressed. 18. Manufacturing process specifications for concrete pipe. 19. Plastic piping materials. 20 Plastic pipe pressure rating vs. temperature. 21. Material requirements and pipe classifications for ABS, PE, and PVC pipe. 22. Manufacturing tolerance ranges for plastic pipe. 23. Data on pressure test ranges for plastic pipe. 24. Measurement tolerances for steel pipe. 25. Maximum allowable chemical content of milli-type steel pipe. 26. Minimum required tensile strength for mill-type steel water pipe. 28. Specifications for materials for cement-mortar lining and coating of steel pipe. 29. Thickness specifications for cement-mortar lining for steel pipe. 30. Thickness specifications for cement-mortar coating for steel pipe. 31. Typical physical properties of wrought iron. 32. Physical data on wrought iron pipe sizes to 12-in. diam. 33. Physical data on wrought iron pipe 14-in. diam. and above. 34. Data on service line materials. 35. Offset of pipe and radius of permissible curve for A-C pipe. 36. Maximum deflection for full length cast-iron pipe. 37. Deflection data on concrete pressure pipe. 38. Pipe joints and their applications. CTD000132