Document gb2X5wjJqed0L4v02baxx7xL9

814 CHAPTER 75 1962 Guide And Data Book ? Rg. 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 are ample for the well-known disc meters now on the market. 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 airing 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 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 excerove pressure at the fixtures, it is frequently desirable to connect hose bibbs ahead of the reducing valve. A. K-h. foundry Ubb (oU riyhL 8. laundry eoapream faucmt. C-1. compression M faucet (Mfr. ti C-2. )(. acpmawi tmk hueet (Mfr. 2L 0. Coabasatioa coatprattna tmihlub faucet* (baft ^paji L Combination compression ridk faucet. F. Soon faucet. G. Spring soft-doting (bacct. /' H. Slow self-doting faucet. (Dafted Caw Mnta recommended exliupufotionl Rg. 7.... Variation of Pressure Loss with Rate of Row for Various Faucets and Coda i aoie j .... rertormance Requirements ot Water Sere, fa. Noras! Tort-Flow limit*, gpa Minimum forf. gpm X........................................... H......... ................................. IX....................................... 2................................ ;........... 3......... ...................................... 4................................................ 1 to 2 to 3 to 5 to 20 34 53 100 16 to 315 28 to 500 48 to 1,000 W x X IX 4 7 12 * American Water Work* AwmiaHm Standard*: Rcswtretioa. The regietretion oa the meter dial ehail indirete the qmatito leemded to be not feat than SS percent nor mare 103 percent at aetaelly rmuil through the meter while it ie being teated at rate* at flow wjtfcia the specified limit* herein coder normal teat flow limita: There ahail be not ^ than SO percent at the aetoal flew recorded when a teat is made et the rate d flee nt forth TTwtwBtw teat Sow. . The principles involved in riring either up-feed or downfeed systems are the same. 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 los 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 fin***, risers, and branches, and indicate the fixtures to be served. Indicate the rate of flow of each fixture. 2. Using Table 2, compute the in fixture, units. weights of the fixtures 3. Determine the total demand in fixture units and, nting Fig. 1 or Fig. 2, find the expected HwnnH in gallons per minute. 4.; Determine the equivalent length of pipe in the main linn, risers, and branches. Since the mm* of the pipes are not known, the exact equivalent length for various fittings, etc., cannot be made. Add the equivalent length*, starting at the street roam Table 4 .... Allowance in Equivalent. Length of Pipe for Friction Loss in Valves and Threaded Rttings* Equrvateif teogtfi of Pip* for Venom Filling* Owsssefor of fitting, tn. 90^0*g Stand ard ED, ft 45-Dog Stand ard Efl, 90-Dog Sid* To* Coupling or Straight Run of Too, Gate Valve, ft ft ft ft Globe Angle Valve, Valve, ft ft X........ 1 0.6 1.5 M 2 1.2 3 Xl........ 2.5 1.5 4 1............... 3 1.8 5 IK-,-- 4 2.4 6 0.3 0.6 0.8 0.9 1.2 IX.......... 5 2............... 7 2K - 8 3............... 10 3K.......... 12 37 4 10 5 12 6 15 7 18 1.5 2 .. 2.53 3.6 4.......... 14 8 21 5............... 17 10 25 6:...:.. 20 12 30 4.0 5 6 * Prom KBS Report BU8S PUmMn* UanuaL 0.2 8 4 0.4 15 8 0.5 20 12 0.6 25 15 0.8 35 18 1.0 45 22 1.3 55 28 1.6 65 34 2 80 40 2.4 100 50 2.7 125 55 3.3 140 70 4 165 60 ^oter Services ^tde 5 . Equivalent Lengths of Iron Pipe to Give Same '!=- Loss as Special Rttings and Apparatus* . Fitting Apparatus Nostnef Diameter of Pip*-- X K 1 iK Vertical hot water tank, , 4n. PIP........................................ Horizontal hot water tank, - M-in. pipe................................................. ffater meters (No valves included) in with K-in. connections-----^ in with 4-in. connections------ in with K-in. connections-----l is with 1-in. connections............ <D with 1-in. connections-----ffzter softener............................................ 4 1.2 6.7 4.6 3.4 -- -- -- 17 56 5 16 28 20 14 9 4.4 50-200 90 64 45 30 14 ' _ -- _ -- -- 115 54 pffcga*. a* weO a* filter*. Friction loaa inrrtesta with use in tbii equipment. ^od proceeding along the service line, the main line in the frttjMmg, and up the nser to the top fixture of the group served. &. Determine the average minimum pressure in the street mam and the minimum pressure required for the operation of the topmost fixture. This latter presure should be 8 to 25 psi. 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 - |P. - 0.434H - P, - P.1 TM (1) when p -- average pressure loss per 100 ft of equivalent length of pipe, psi. P, -- pressure in street main, psig. Pfm minimum pressure required to operate topmost fixture, psig. Pm pressure drop through water meter, psi. B m 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 converted to pounds per square inch by multiplying by 0.434, replaces the street main pressure, and the term 0.434 H in Equation 1 is added instead of sub tracted in calculating the term p. Id 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 bus of pipe from Figs. 3, 4, or 5. Example B: Assume a minimom street main pressure of 55 prig; a height of topmost fixture (a urinal with flush valve) above Table 6.... Computation of Brandi Size in Example 2 fixtures No, and Kind fixture tiniti (From Fobis 2 and Note c) Demand fig. 2) gpm Pip* Sum [From Fig. 4) 3 flush valves 3x6 - 18 X (2 x 2) - 3 K (3 x 1) - 2.25 23.25 38 IK 815 Table 7.... Allowable Number of }-n. Connections for -- ' Various Sizes of Water Pipe fipe Size, m. Average Demand 100 Fetid Demand X H l IK Hi 2 2K 3 4 11 43 10 6 20 12 30 20 50 35 70 60 125 100 200 165 streetmt'" 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 nits; and that the water closets are flush-valve operated. Find the required size 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 the topmost fixture is 15 prig. From Table 3 it is evi dent that several sizes of meters would adequately measure this flow. For a trial computation choose the iK-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 tii* 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 rises. If the computed pipe sizes 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 pressure loss per 100 ft of equivalent pipe is 12 X 100/(100 + 50) = 8 psi. Assuming that the corrosive and firing properties of the water are such that Fig. 4 for fairly rough pipe is applicable, a 2-in building min will be adequate. The suing of the branches at the building main, the rieert, and fixture branchet 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 the 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 IK 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. Flush Valves Served by Various Sizes of Water Pipe* Pip* Size, in. No. of I-in. Fbnh Vafvet IK j IK 2-4 2 5-12 2K 13-25 3 26-40 4 41-100 * Two H-ta. Stab valvre are --luniud equal to one 1-in. flush valve, but eaa bo screed by a 1-in. pip*. Water pip* string most be tempered by consideration d demand (actor, available pressure, and length of ran.