Document 2mJDVnXbNvwqexGdKn0ZaddN

HEATING VENTILATING AIR CONDITIONING GUIDE 1943 It is evident that any pipe size adequate to take care of the probableflow will also be more than ample to take care of the average flow, and hence the latter has no bearing on the pipe size. MAXIMUM FLOW An estimate of maximum flow for various fixtures regardless of type of building with the water at about 35 lb pressure is given in Table 1. To obtain the probable flow from Table 1, it is necessary to multiply the maximum flow by a factor of usage, and this factor varies with the Table 1. Approximate Maximum Flow from Fixtures under Normal Water Pressures Fixtures Water-closets, flush valve............. Water-closets, flush tank..... ........ Urinals, flush valve____________ Urinals, flush tank__,; Urinals, automatic tank________ Urinals, perforated pipe per footLavatories_____________________ Showers, 4 in. heads, in. inlets. Showers, 6 in. heads or larger^.... Needle bath___________________ Shampoo spray_____ ___________ Liver spray__________ _________ Manicure tableBaths, tub'__________________ .... Kitchen sink_________ :_________ Pantry sink, ordinary: Pantry sink, large bibb... Slop sinks: Wash trays._______ ;____________ Laundry tray,,___ _____________ Garden hose bibb.......................... Colo Water (Gallons per Minute) 45a 10 30=1 10 1 10 3 3 6 30 1 2 m 5 4 2 6 6. 3 6 10 Hot Water (Gallons per Minute) 0 .0 0 0 0 0 3 3 .6 30 1 2 m 5 4 2 6 6 3 a 0 Actual testa on water-closet flush valves indicate 40 gpm as the maximum rate of flow with 30 lb pres sure at the valve; this would increase to 60 gpin (about 50 per cent) at 90 lb pressure. The 45 gpm has been taken as an average flow; possibly, with very low pressures just sufficient to operate the flush valve. 30 gpm could be allowed with safety. Urioal flush valves would vary proportionately in the same* manner. type of occupancy and with the number of fixtiires in the installation. With only two fixtures it is possible that, both will at some time! be in: operation simultaneously. With 200 fixtures, however, it is unlikely that the entire 200 would ever operate at the same time. Consequently,, the factor of usage becomes smaller as.the number.of fixtures becomes greater, all other things being equal., y , ........ V, The maximum flow per fixture for cold water should be totaled inde pendently of that for hot water, and the sum of the two may be used in computing the probable flow through the incoming cold water supply main. ; . FACTOR OF USACE ,,/ The principal plumbing fixtures subject to wide variation in water demand is a flush valve closet, and also shower baths, especially those in 820 CHAPTER 46. WATER SUPPLY PIPING AND WATER HEATING gymnasiums, and buildings of that type, and also in manufacturing plants where the outgoing shifts create a heavy peak. The curves of Fig. 1 suggest a method of selecting a factor of usage.. The curve at the left should be followed for hot water piping and for cold water if the system has gravity tank closets, while the curve to the right allows amply for the influence of flush valve closets. For example, if the product of the number of plumbing fixtures in a building multiplied by the proper values in Table 1 totals say 620 gal of water as the maximum flow, when using flush tank closets, the factor of usage from Fig. 1 will be about 23 per cent, and the probable flow will be 620 X 0.23 = 143 gpm. This is the first item to be determined in the design of a water supply system. In a building using 143 gpm.no serious difference in the size of the main supply pipe would be occasioned by use of flush valves, since the factor of usage with the latter would be increased only to about 25 per cent or 155 gpm. The curves of Fig. 1 are believed.conservative for toilet rooms in large office buildings which have early business hour peaks, especially in the men's toilets, but may not be conservative enough for plants such as gymnasiums and manufacturing plants where heavy peak demands occur during certain hours. The proper usage percentage for such wises must be a matter of judgment and might properly approach 100 per Cent. The average flow will usually be considerably smaller. Example 1. Assume that in a normal building, such as a residential hotel or an apart ment house, there are 50 flush valve water-closets, 50 lavatories, 50 sinks and 50 baths, and that it is desired to determine the probable flow in a line supplying all of these fixtures with both cold and hot water. Cold Water 50 W. C. x 45 gpm_______ 2250 gpm 50 Lava, x 3 gpm_______ - 150 gpm' 50 Sinks x 4 gpm 200 gpm 50 Baths x 5 gpm 250 gpm Maximum flow.2850 gpm Fig. 1 shows a factor of usage of 9 per cent. Probable flow of cold .water is 2850 X 0.09.....1TM---.------ ---- ----------- Hot Water 50 Lavs, x 3 gpm150 gpm 50 Sinks x 4 gpm__ ......__ 200 gpin 50 Baths x 5 gpm 250 gpm Maximum-flow.::..------------ 600 gpm; Fig. 1 shows a*:factor of usage of 23 per cent. . Probable flow of hot water is 600 X 0.23-- 138 gpm Total for main supplying cold and hot water (2850 + 600) X 0.08 ;__________________ 276 gpm It should be noted that this is a rate of flow or an instantaneous demand. i WATER PRESSURE The usual practice in buildings of moderate height is to place the water supply mains near the basement ceiling, with up-feed risers feeding the various fixtures on the upper floors. In tall buildings, the pressure due to the weight of the water becomes so great as to limit the service to vertical sections not exceeding, about 20 stories in height. ,Beyond this approxi mate limit the valves oil the lower-stories will be noisy.. For these reasons, the considerations of this chapter are limited to horizontal.mains and to risers which serve not more.ihan 20 stories. In taller buildings it is usual to install separate horizontal mains .for each superimposed zone. /. ' - -v ' The minimum practicable size of;; piping for any water system is 821