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                    140  Chapter 4  Quantities of Water and Wastewater Flows


                                         of three dwellings per acre (7.415 unit/ha), an average market value of USD 125,000 per dwelling
                                         unit, and a potential evaporation of 0.28 in./d (7.11 mm/d) on the maximum day.
                                         Solution 1 (U.S. Customary System):
                                             Average maximum and peak daily domestic demands per dwelling unit:
                                         By Eq. 4.20: Q domestic    157   3.46 M   157   3.46   125   590 gpud
                                          By Eq. 4.19: A   0.803 D  1.26    0.803>3 1.26    0.20 acre per dwelling unit
                                                                                     4
                                                                   4
                                         By Eq. 4.18: Q sprinkling   1.63   l0 A (E   P)   1.63   l0   0.20   (0.28   0)
                                                                                         913 gpud excluding precipitation
                                             For management:
                                             Q max day   Q domestic   Q sprinkling   590   913   1,503 gpud.
                                             By Eq. 4.21: Q peak h   334   2.02 Q max day   334   2.02   1,503   3,640 gpud
                                             For design based on 200 dwellings:
                                                   From Table 4.11: Q max day   1,503   0.4 (1,000)   1,903 gpud
                                                   From Table 4.11: Q peak h   3,640   0.7 (1,000)   4,340 gpud

                                          Solution 2 (SI System):
                                             Average maximum and peak daily domestic demands per dwelling unit:
                                          By Eq. 4.20a: Q domestic    594   13.1 M   594   13.1   125   2,232 Lpud
                                          By Eq. 4.19a: A   1.016 D  1.26    1.016>(7.415) 1.26    1.016>12.4836   0.08138 ha/unit
                                          By Eq. 4.18a: Q sprinkling   6,003 A (E   P)   6,003   0.08138   (7.11   0)
                                                                                       3,473 Lpud excluding precipitation
                                             For management:
                                             Q max day   Q domestic   Q sprinkling   2,232   3,473   5,705 Lpud.
                                             By Eq. 4.21a: Q peak h   1,264   2.02 Q max day   1,264   2.02   5,705.2   12,789 Lpud
                                             For design based on 200 dwellings:
                                                   From Table 4.11: Q max day   5,705   0.4 (1,000)   3.785   7,219 Lpud
                                                   From Table 4.11: Q peak h   12,789   0.7 (1,000)   3.785   15,438 Lpud




                    4.5  DEMAND AND DRAINAGE LOADS OF BUILDINGS
                                         The demand load of a building depends on the number and kinds of fixtures and the prob-
                                         ability of their simultaneous operation. Different fixtures are furnished with water at differ-
                                         ent rates as a matter of convenience and purpose. Expressed in cubic feet per minute
                                           3
                                         (ft /min), or liter per second (L/s) for fixture units, these rates become whole numbers of
                                         small size. Common demand rates are shown in Table 4.15.
                                             It is quite unlikely that all fixtures in a building system will draw water or discharge it
                                         at the same time. A probability study of draft demands leads to the relationships plotted in
                                         Fig. 4.5. In practice, the values shown are modified as follows:
                                             1. Demands for service sinks are ignored in calculating the total fixture demand.
                                             2. Demands of supply outlets, such as sill cocks, hose connections, and air conditioners,
                                                through which water flows more or less continuously for a considerable length of
                                                time, are added to the probable flow rather than the fixture demand.
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