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1204' CHAPTER 49 1958 Guide Table 3. Performance-Requirements of Water Meters* < Size In. if----------------------------------------- r......... -- iH---------------:-----------------------. 9. ' 9 A.........-................................. ----6ii. Normal Test-Flow Limits GPM Ito 20 2 to 34 3 to -53 5 to , 100 >i . .8 to 160' 16 to . 315 28 to '600 48 to 1.000 Minimum Test-Flow GPM M id iH 2 -4 : 7 12 * American Water Works Association Standards: Registration. ' The registration on the meter dial shall indicate the quantity recorded to be not less than 98 peroent nor more than 102 percent of the water actually passed through the meter while it is being tested at rates of flow within the specified limits herein under normal test flow limits: There shall.be not less than 90 percent of the actual flow.recorded when a test is made at the rate of flow set forth under minimum teat flow. 1 \ The water demand for hose bibbs or other large, demand fixtures taken off the building main is frequently the cause of inadequate water supply to the upper floor of a building. This condition may be prevented by sizing the distribution system so'that`the pressure drops from the [street main to all fixtures are the same. It is good practice to maintain the building main of, ample size (not.less than l;in. where possible) until all branches to hce bibbs .have been connected, .Where the street main pressure is e!xcessiye[ and a pressure reducing valve is used to prevent water hammer or exces sive pressure at the fixtures,, it is frequently, .desirable '-to connect hos^ bibbs ahead of the.reducing valve. . , , . .... The. principles :involved iin sizing either up-feed, or downTfeed.systems are, the same. The principal difference in. procedure is that ,in the ,downfeed system, the difference in elevation.between-the house tank,and the fixtures provides, the pressure required to overcome pipe friction. , - Procedure for Sizing Cold Water Systems "iv! The recommended procedure for sizing piping systems is, outlined infolf lowing paragraphs 1 to 6, inclusive. 1. Draw a sketch of the main lines, risers, and branches, and indicate the fixtures to be served. Indicate the rate of flow of each fixture. Table 4. Allowance in Equivalent Length of Pipe fob Friction Loss in Valves and Threaded Fittings Diameter of Fitting In. 90 Deg Standard Ell Ft u%_______ . i 1U 2. ' 2a 4) .--______________ 3)44 ' ................... . K 6-, i 2 2.5 3 4 5 7 8 10 12 14 17 20 Equivalent Length of Pipe for Various Fittings 45 Deg. Standard Ell . Ft 90 Deg Side Tee Ft Coupling or Straight Run of Tee Ft 0.6 1.2 1.5 1.8 2.4 3 4 .5 6 7. - .8 '.. . 10 12 '1.5 3 4 5 6 7 10 12 15 18 21 25 30 0.3 0.6 0.8 0.9 1.2 1.5 2 2.5 ; 3 3.6 4.0 5 6" Gate Valve Ft 0.2 0.4 0.5 0.6 0.8 1.0 1.3 1;6 2 2.4 2.7 3.3 4 Globe Valve Ft Angle Valve Ft 8 15 20 25 35 45 55. 65 80 100 ,125 140 . 165 4 8 12 15 lS 22 28 : .34 . i 40 r . ; 55 .: 70 : - 80 WaterServices 1205 2. Using Table 2, compute the demand weights of the fixtures in.fixture units. 3. Determine the total demand in fixture units and, using Fig. 1 or Kg. 2, find the expected demand in. gallons per minute. 4. Determine the equivalent length of pipe in the main lines, risers, and branches. Since the sizes of the pipes are not known, the exact equivalent length for various fittings, etc., cannot be made. Add the equivalent lengths, starting at the street main and proceeding along the service line; the main line in the building,and up the riser to the top fixture of the group served;. 5. Determine the average minimum pressure in the street main and the.minimum pressure required for the operation of the topmost fixture. This latter pressure should be 8 to 15 psi. : 6. Calculate, by means of Equation 1, the approximate design value of the average pressure drop per 100 ft of pipe in the equivalent length determined in paragraph 4. p - [I? - 0.43/1 - 10] where P = average pressure loss per 100 ft of equivalent length of, pipe,' psi.' P -- pressure in street main,.psig9 : (1) Table 5. Equivalent Lengths of Ihon Pipe to Give -Same Loss as Special Fittings and Apparatus 1 Fitting Apparatus Nominal Diameter of Pipe--Inches H H 1 1M 30-gal Vertical hotrwater tank, % in. pipe. . 4 .- . 30-gal Horizontal hot-water tank, in. pipe.. 1.2 Water meters (No valves included) % in. with 14 in* connections1. "6.7 % in. with % in. connections; : " 4.8 1 in. with 1 in: connections. ............................ 1% in. with 1 in. connections........................... :_ Water softener................. ............ .. --- . .17 ; 56 5 i 16 28 . 20 14 9 ' 4.4 50-200 90 64 ,45 ; 30 14 ' _ .. . ii5` '54 ` >.: R -- height of highest fixture above street, main, feet. A.= equivalent length determined in paragraph 4, feet. - - the s,ysteln is of the down-feed supply from a gravity tank, the height of water m the tank, converted to pounds per square inch by, multiplying by 0.43, replaces the street main pressure, and the term 0.43 H in Equation 1 is'added instead of sub tracted in calculating the term p- In this'case,'ff will be the vertical distance of the fixture below the bottom of the tank. ... 7. From the expected rate of flow, determined as in paragraph 3, and the value of p, calculated as in paragraph 6, choose the sizes of pipe from Figs. 3', 4 or 5. Example 2: Assume a minimum street main pressure of 55 psig; a height of topmost nxture above street main of 50 ft; a developed pipe length from water main to highest nxture of 100 ft; a total load on the system of 50 fixture units; and that the water' closets are flush-valve operated. Find the required size of supply main. T w a 0TM' ^r.9m F'S- 2 the estimated peak demand is found to be 51 gpm. From Fn 6 + *-* !s ev'dent that several sizes of meters would adequately measure this flow. th B ina computation choose the 1J4 in. meter. From Fig. 6 the pressure drop tnrough a 1)4 in. disc-type meter for a flow of 51 gpm'is found to be 6.5 psi; Then the pressure drop available for overcoming friction in pipes and fittings is 55 - (15 + 50 X 0.43 + 6.5) = 12 psi. 6 of tL* tci!-point it is necessary, to make some estimate of the equivalent pipe length exani ngs on the direct line from the street main to the highest fixture. The nine -ec!uiyalcnt length of the various fittings cannot now be determined since the known263 f the building main, riser, and branch leading to the highest fixture are not selpM? as ?et-' but a first aPProximation is necessary in order to make a tentative minin?i,0f piR sizes. If the computed pipe sizes differ from those used in deter- mng the equivalent length of pipe fittings, a recalculation will be necessary, using