Document 6RJYjkX5381vbvp8vd31GR00o

770 CHAPTER 56 1960 Guide 7| (So* manufacturer's data for exact vafoe far meter umd) fig. 6.... Pressure Losses in Disc-type Water Meters varies considerably with the design even in meters of the same nominal size. The values given in Table 5 tire ample for the well-known disc meters now on the market. The water demand for hose bibbs or other large demand fixtures token 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 1 in. where possi ble) until all branches to hose bibbs have been connected. Where the street main pressure is excessive and a pressure reducing valve is used to prevent water hammer or excessive pressure at the fixtures, it is frequently desirable to connect hose bibbs ahead of the reducing valve. S. tawrity coespresaon faucet. C-l. K"*- compressor mk faucet (Mfr. I}. C-2. K-*- compressor) sink faucet (Mfr. 2). 0. Combination compressor bafhfub faucets (both open). E. Combination compression sink faucet. f. lorn faucet. G. Spring *off*doiing faucet, ft. Slow self-dosing faucet. iDosbod fine* indicate recommended extrapolation) fig. 7.. .. Variation of Pressure Loss with Rote of Row for Various Faucets and Cocks Table 3__ _ Performance Requirements of Water Meters" Size, (a Normal fori-How Minimum Test-Flow, limits, gpm gpm 1....................................... ................................... 2....................................... 3....................................... 4....................................... 6....................................... 1 to 20 2 to 34 3 to 53 5 to 100 8 to 160 16 to 315 28 to 500 48 to 1,000 3 H iX 2 4 7 12 * A means) Water Works Attestation Standard*: Becistntioo. The reerstretiaa cm the meter die) dull indicste the quantity recorded to be not leaa tbu #8 percent nor more than 103 percent of the water sctoslly pissed through the meter while it is beint teeted et rates of flow within the specified limit* hems under normal test flow limite: Tbere shall be not lees than SO percent of the sntsial Bow recorded when a tea* ii made at the rate of flow set forth under TM:p:--" teat flow. The principles involved in sizing either up-feed or downfeed systems are the 6ame. The principal difference in pro cedure is' that in the down-feed system, the difference in elevation between the house tank and the fixtures provides the pressure required to overcome pipe friction, and thus re duces pipe sizes, since friction pressure loss and height pres sure loss are not additive as with an up-feed system. Procedure for Sizing Cold Water Systems The recommended procedure for sizing piping systems is outlined in following 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. 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 Fig. 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 rises 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 Table 4.... Allowance in Equivalent Length of Pipe for Friction Loss in Valves and Threaded fittings* Equivalent Length of Pipe for Various Fitting* Oiaaofor ft ft ft ftof Filling, In. 90-Deg Standord Bl, ft 45-Dug Stand ard Bl, 90-Oog Sids Te Coupling or Straight Run of Tee, Goto Volvo, ft ft . Globe Valve, Anglo Valvo, %.... l 0.6 1.5 0.3 0.2 84 x.......... 2 1.2 3 0.6 0.4 15 8 H.......... 2.5 1.5 4 0.8 0.5 20 12 1............... 3 1.8 5 0.9 0.6 25 15 IK........ 4 2.4 6 1.2 0.8 35 18 IK.......... 2............ 2K.......... 3............... 3K.......... 5 7 8 10 12 37 4 10 5 12 6 15 7 18 1.5 1 0 45 22 2 1.3 55 28 2.5 1.6 65 34 3 2 80 40 3.6 2.4 100 50 4.............. 14 8 21 5............... 17 10 25 6............... 20 12 30 4.0 2.7 125 55 5 3.3 140 70 6 4 165 80' : Flan NB8 Report BMSM Pltnitiv Manual. Water Services 771 Table 5___ Equivalent Lengths of Iron Pipe to Give Some Loss as Special Fittings and Apparatus Table 7.... Allowable Number of Connections for Various Sizes of Water Pipe X -K 1 iK 30-gal Vertical hot water tank. H-in. pipe........................................ 30-gal Horizontal hot water tank. K*in. pipe........................................ Water meters (No valves included) K is. with K-in. connections. . K in. with K-iu- connections----K in. with 3i-in. connections___ 1 in. with 1-in. connections......... IK *n. with 1-in. connections. .. Water softener..................................... 4 1.2 6.7 4.8 3.4 -- -- 17 5 28 20 14 9 4.4 50-200 56 -- 16 -- 90 -- 64 -- 45 -- 30 115 14- 54 ---- * Tbs Ji,:f - should check manufacturers' data for maximum losses tkraofli softeners, as well as filter*. Friction loss increases with use in this equipment. and proceeding along the service line, the main line in the building, and up theriaer 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 25 pri. 6. Calculate, by means of Equation 1, the approximate de sign value of the average pressure drop per 100 ft of pipe in the equivalent length determined in paragraph 4. p - (/>. - O.WH - P, - PsJ-ir . (1) where p tm average pressure loss per 100 ft of equivalent length of pipe, psi. P, " pressure in street main, psig. pf = minimum pressure required to operate topmost fixture, psig Pm -- pressure drop through water meter, psi. H-tm height of highest fixture above street main, feet. L equivalent length determined in paragraph 4, feet. 'If the system is of the down-feed supply from a gravity tank, the height of water in the tank, converted to pounds per Square inch by multiplying by 0.434, .replaces the street main pressure, and the term 0.434 in Equation 1 is added instead of sub tracted in calculating the term p. In this case, H 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 sues of pipe from Figs. 3, 4, or 5. Example t: Assume a minimum street main cressure of 55 prig; a height of topmost fixture (a urinal with flush valve) above Table 6.... Computation of Branch Size in Example 2 Pipe Size, in. K K 1 IK IK 2 2)i 3 4 Average Demand l 4 10 20 30 50 70 125 200 100 Percent Demand 1 3 6 12 . 20 35 60 100 165 street main of 50 ft; a developed pipe length from water main to highest fixture 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 rise of supply main. Solution: From Fig. 2 the estimated peak demand is found to be 51 gpm. From Table 1, the minimum pressure required to operate tee topmost fixture is 15 psig. From Table 3 it is evi dent that several sizes of meters would adequately measure this flow.. For a trial computation choose the-1 K-in. meter. From Fig. 6 the pressure drop through a lK-in. disc-type meter for a flow of 51 gpm is found to be 65 psi. Then the pressure drop available for overcoming friction in pipes and fittings is 55 -- (0.434 X 50 + 15 + 65) = 12 psi. At this point it is necessary to make some estimate of the equivalent pipe length of the fittings on the direct line from the street main to the highest fixture. The exact, equivalent length of the various fittings cannot now be determined since the pipe sizes of the building main, riser, and branch leading to the highest fixture are not known as yet, but a first approxima tion is necessary in order to make a tentative selection of pipe sizes. If the computed pipe rises differ from those used in deter mining the equivalent length of pipe fittings, a recalculation will be necessary, using the computed pipe sizes for the fittings. For the purposes of this example assume that the total equiva lent length of the pipe fittings is 50 ft. Then the permissible presure loss per 100 ft of equivalent pipe is 12 X 100/(100 + 50) = 8 pri. Assuming that the corrosive and caking properties of the water are such that Fie. 4 for fairly rough pipe is applicable, a 2-in. building main will be adequate. The airing of the branches of the building main, the risers, and fixture branches follows the principles outlined. For exam ple, assume that one of the branches of the building main car ries the cold water supply for 3 water closets, 2 bathtubs, and 3 lavatories. Using tee permissible pressure loss of 8 psi per 100 ft, the size of branch determined from Table 2 and Figs. 1 and 4 is found to be lVi in. Items entering the computation of pipe size are given in Table 6. Tables 7 and 8 have been used to simplify the sizing of local branch piping. ' .Velocity must also be' considered in sizing water supply ..- Table 8 . . ... Allowable Number of' 1 -in. Rush Valves "Served by Various Sizes of Water Pipe* No. and Kind 3 flush valves. 2 bathtubs____ ! Fixture Untl* (From Table 2 and Note a} Fig. 2) gp* Pipe Size (From Fig. 4) in. .3x6 18 " % (2x2J;-3 - H(3x IV *;:'2.25 . 23:25 38 IK ' Pipe Size, in. No. of J-in. Flush Voire* IK IK 2 2K -3 4 ., 1 2-4 5-12 13-25 26-40 41-100 - * Two M-is. flash valve* sre sssumrd equsl to one 1-fa. flush valve, bat can be served by a 14n. pipe. Water pipe sizing most b* tempered by consider*tioo <4 demand factor, available pressure, sad lesftb of ran. 1`'