WATER CONSUMPTION 22. In General.-The quantity of water required for any use varies greatly, especially so in residences, where leakage, waste, quality, and temperature are influencing factors. Consumption in cities and villages is usually reckoned on the "per capita" basis and includes all uses, such as domestic, fire, sprinkling, manufacturing, and municipal. In 111 cities with a population of 25,000 or over, the consumption was as follows: maximum 324, average 105, minimum 31 gal. per capita per day. In 76 cities with less than 25,000 population, the consumption was: maximum 149, average 61, minimum 10 gal. per capita per day. Per capita rate in cities usually lies between 60 and 270 gal. per day with an average use of about 100 gal. per day. 23. Residences.-The quantity of water used in residences must necessarily be less than the above averages as it includes only household use, lawn and garden sprinkling. The minimum and maximum consumption in a residence is 42 and 151% of the average, respectively. Minimum usually occurs from 3 to 4 A.M., average between 7 and 9 P.M., and maximum from 9 to 10 A.M. This will vary according to the number of fixtures, leakage, careless use, etc., but with all of the uncertainties, the average residence consumption will be from 15 to 50 gal. per capita per day. From the experience of the army cantonments in this country, it was learned that 30 gal. per capita per day is sufficient for all domestic needs, inclusive of sewer flushing, but exclusive of lawn sprinkling and water allowed to rur to prevent freezing. 24. Factories and Industries.-The consumption will vary greatly with the nature of the work involved, with the availability of the supply, and the number of, and character of the plumbing fixtures in use. No hard and fast rule can be laid down for this class of consumption. In Table 7 are given some data that will give a rough notion of the consumption that might be expected. TABLE 7.-CONSUMPTION OF WATER BY FACTORIES AND INDUSTRIES 25. Apartment Houses.-The consumption in apartment houses is not greatly different from what we would expect to find in residences, except that there is a comparatively small amount of laundry work done, and usually no lawn or garden sprinkling. The meter readings of nine of these apartment houses give an average of 50 gal. for this type of consumption, with a minimum of 35.4 and maximum of 75 gal. per capita per day. The meter readings of 13 apartments, some having special uses, give a minimum of 35.7 gal., an average of 74.4 gal., and maximum of 181 gal. per capita per day. The size of the apartment building, i.e., number of separate apartments, does not influence the per capita rate. In large cities the consumption appears to be greater than in small cities. Municipally owned plants with low rates tend to promote lavish use and waste of water as compared with privately owned plants. Where water is used for special purposes, such as pumping air for thermostat operation, water for cooling, and for ice machines, the consumption may run from 75 to 180 gal. per capita per day. In Boston, Dexter Brockett found that the average consumption of 339 apartment houses was 35.6 gal.per capita per day and that the best class used 59 gal., first class, 46 gal., moderate class, 32 gal., and the poorest class, 16.6 gal. per capita per day. 26. Schools. The average consumption (meter readings for 6 mo.) of 15 schools was 22 gal. per capita per day, the minimum of 12 public schools was 8.5 gal., and maximum, 45 gal. per capita per day. Three parochial schools gave a minimum of 4 gal. and a maximum of 24 gal. per captia per day. The number of pupils in a building did not seem to influence the rate of consumption. Average 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 -AM Hours of the day FIG. 2. -P.M. Schools where domestic science was taught and shower baths used, show a minimum of 13 gal., a maximum of 45 gal., with an average of 30 gal. per capita per day, whereas in schools where neither domestic science was taught nor shower baths used, the minimum was 8.5 gal., maximum 39 gal., with an average of 19 gal. per capita per day. 27. Milk Condenseries.-Condenseries use from 2 to 3 gal. of water per pound of milk with a possible average of 2.65 gal. per pound of milk. 28. Institutions.-Institutions, especially those of state or public ownership, are lavish users of water as a rule. The average water consumption for 37 institutions was 104 gal. per capita per day, 20 gal. minimum, and a maximum of 310 gal. Of this number of institutions, a Y.W.C.A. Camp, a Children's Home, and a University were the minimum users of water with a consumption of 20 to 25 gal., whereas a State Hospital used the greatest amount-viz., 310 gal. per capita per day. The minimum consumption for 15 state hospitals and asylums was 50 gal. per capita per day, a maximum of 310 gal., with an average of 63.55 gal. 29. Variations in Rates of Consumption.-The consumption of water varies with the seasons, temperature, day of the week, and with the hour of the day. Seasonal fluctuations vary from a minimum of 75% to a maximum of 125% of the yearly average. Effect of temperature is shown by a record from Detroit, Mich., on an extremely cold day when the consumption for the entire day was 150% and over, of the yearly average. This excess was waste and was done to prevent freezing. On an extremely hot day in the same city, the consumption went up to 175% of the average. Sunday consumption was found to be from 50 to 85% of the daily average. Fig. 2 illustrates the hourly variation in consumption in per cent. of the average daily rate for several classes of consumption. The curves represent average conditions in American cities. C. M. Saville, Sup't. of Waterworks, Hartford, Conn., measured the maximum rate of consumption of a number of consumers of different classes, a partial list of which is given in Table 8. It will be noted that the maximum consumption of a tenement house occupied by 110 people, an apartment occupied by 40 people, and a family of 6 people is nearly equal in amount. However, the duration of these maximums was much greater for the larger users, being 3 minutes for the residence and 70 minutes for the apartment house. TABLE 8.-MAXIMUM OBSERVED RATES OF CONSUMPTION IN HARTFORD, Conn. 30. Meters. A meter should be selected for a given service so that the ordinary rate of flow of water will be approximately the rate at which the accuracy of the meter is a maximum. Too often the selection of the size of a meter is governed by the desire to cut down the loss of head between the main and the faucet, than it is on the rate of flow in the service pipe. Under such conditions, the service rendered does not come within the limits of accurate registry of the meter, and as a result the meter greatly under registers. To meet these conditions, with a view to economy as well as efficiency, Saville says it is desirable to consider: 1. The installation of larger service pipes instead of larger meters. 2. Proper provision in the house-piping system, to meet the demands of modern plumbing, instead of installing larger meters. A large-sized riser pipe, acting as a house standpipe, where flushometer fixtures are installed, might give a better service than could be obtained by use of a larger meter. 3. The selection of meters properly designed for the particular use to which they are to be put. So far as accuracy of registration and durability goes there seems little to influence choice between any of the meters now put on the market by the half-dozen or more reputable manufacturers of water meters. So far, however, as loss of head is concerned, meters of different makes now on the market show considerable variation. A meter should be set where it will not freeze and preferably should have a breakable bottom. Its location should also be chosen with a view to making it accessible for reading and removing for testing. TABLE 9.-RATES OF USE OF WATER BY PLUMBING FIXTURES 10 continuously and four flushometer closets operated in quick succession.. 90.0 TABLE 10.-SUMMARY OF DATA ON TEN MAKES OF DISK METERS Guaranteed accuracy-Maximum rate, 98 to 99 %; medium rate, 98%; minimum rate, 90 to 95%. TABLE 12.-MAXIMUM PROPER RATE OF FLOW AND LOST HEAD THROUGH DISC METERS, TOGETHER WITH THE LENGTH OF STRAIGHT PIPE WHICH GIVES THE SAME LOST Size of meter (inches) HEAD AT THIS RATE (Adapted from C. M. Saville, Hartford, Conn., Tests on Meters) 31. Pressure of Water.-Pressure of water is usually expressed in pounds per square inch, p, and head or depth of water in feet, h. This relationship holds for a static condition whether the pressure or head is created by gravity as from a tank, or by direct pressure from a pump or ram. These same quantities expressed in pounds per square foot are P = 62.5 H H = 0.016P (lb. per sq. ft.) (head in feet) The coefficient of P and H will vary slightly with the temperature, being greater for temperatures near 39.1 deg. F. and less for those near the boiling point. For all practical computations it is not necessary to take the variation into consideration. Where water is flowing in a pipe line from one source, as from a tank at elevation h above point under consideration, the pressure at the end of the pipe is expressed as follows: (lb. per sq. in.) p = 0.434h (ho + hs+ hi+hi) = = in which hu= head required to produce velocity of the water, h head to overcome friction in the pipe, hi head lost at entrance, and hi= head available at the end of the pipe, but at the same elevation as point at which p is measured. 32. Flow of Water in Pipes.-Many scientists have derived formulas for the flow of water in pipes, from experiments and theoretical considerations. TABLE 13.-PRESSURE REQUIRED TO RAISE WATER TO TOP STORY OF BUILDINGS WITH TOP (Hazen & Williams' tables used for loss of head) Notes on Table 13.-Only one riser pipe is assumed to supply building and the elevation chosen is sufficient to give 25 lb. on highest floor from either municipal, elevated, or pneumatic tank supply. Friction loss based on maximum rate, assumed at twice the average for 24 hr. 20% of friction loss in pipe and velocity head is added to cover loss in elbows and faucets. Where number of people are less or consumption per capita is less, the smaller sizes of pipe can be extended to higher stories. ་ * Supply assumed to come from public supply or private in basement or at ground level; velocity for average supply 3 to 4 ft. per second. If supply is to come from elevated tank on roof, then the largest size of pipe should extend from basement to roof. Example.-(a) What size of pipe should be chosen for an 11-story building supplying 1100 people with tank on roof? (b) With municipal supply? (a) 3 in. for full 11 stories. (b) 3 in. for first 2 stories, 21⁄2 in. for next 3 stories, 2 in. for next 2 stories, 11⁄2 in. for next 2 stories, 14 in. for the next, and 1 in. for the last story. Example.-What size of pipe should be used for a 6-story building supplying 1200 people with 4500 gallons of water? In this case the size should be chosen for the supply and not the floor, so a 3-in. should be used. The pressure required would be slightly less than 65 lb. One of the simplest and most commonly used is the Darcy formula in which |