Document 1QE4ryLXmnQGyV5qxaY0jeOvj

978 CHAPTER 48 1950 Guide Table 1. Proper Flow and Pressure Required During Flow for Different Fixtures Fixture Flow Pbbuubs* Flow gpm Laundry tub cock--i in.............................................................. 8 12 10 5 5 5 -12 15 10-20 15 30 3.0 2.5 4:5 4.5 6.0 5.0 5.0 3.0 20-40*15.0 5.0 . * Flow pressure is the pressure in the pipe et the entrance to the pertieulsr fixture considered.' h Wide range due to variation in deeigo and type of fioah-valTe closets. outlets other than those listed in the table of fixture units is not yet in cluded in the estimate. The demands for outlets (such as hose connec tions, air conditioning apparatus, etc.) which are likely to impose con.tinuous demand during times of heavy use of the weighted fixtures, should be estimated separately and added to the demand for fixtures used in termittently, in order to estimate the total demand. SIZING COLD WATER SUPPLY PIPING So far, the information presented makes possible the determination of the design rate of flow in any particular section of piping. The next gen eral step is to determine the size of piping. As water flows through a pipe, the pressure continually decreases along the pipe, due to loss of energy from friction. The problem is then one of ascertaining the minimum pressure in the street main, and the minimum Table 2. Demand Weights of Fixtures in Fixture Units* Fixture or Group* Occupancy Tyfb of Supply Control Weight in Fixture Units M. II .,*1, ,1 ; Faucet___ Shower head_________________ Private.--..----- ------- ----- Mixing valve______ Flush valve for closet -------- ^ ^_ 10 5 10 5. 3 2 4 4 3 4 6 3 1 2 2 8a 2 23 3 *' - For supply outlets likely to impose continuous demands, estimate continuous supply separately and add to total demand for fixtures. . , ... . , b pgr fixtures not listed, weights may be assumed by comparing the fixture to a listed one using water in wimflnr nnantititt and at similar rates. _ ... , . . ,, .. .. .... The given weights are for total demand. For fixtures with both hot and cold water supplies, the weights, for separate may be taken as H the listed demand for the supply. Water Services 979 No. 1 far system predominantly for flush valves. No. 3 for system predominantly for flush tanks. Fig 1. Estimate Curves fob Demand Load pressure required for the operation of the topmost fixture. (A pressure of 15 psi is ample, for flush valves, but reference should be made to the manufacturers' requirements. A minimum of 8 psi should be allowed for other fixtures.) The pressure differential thus obtained will be available for overcoming.pressure losses in the distributing system, and in over coming the difference in elevation between the water main.and the highest fixture.' '; The pressure loss, in pounds per square inch, caused by the difference in elevation between the street main and the highest fixture, may be ob tained by multiplying the difference in elevation in feet by 0.43. When waiter flows through a pipe, friction occurs as the result of the sliding of water particles past one another. If the pipe wall is rough, the rouglmess projections cause additional friction, owing to the develop ment of increased turbulence in the flowing water. As the water flows along a uniform pipe, the pressure decreases as a result of a dissipation of energy arising from the internal friction set up by viscosity of the water. This loss in energy is shown by the loss of pressure. The pressure loss li ! I * i! >!i fP ,i: !!l