Document 6B0aYe5NmonNOpMDwz30710X9

American Society of Heating and Ventilating Engineers Guide, 1928 quantity of water is the pressure necessary to overcome friction in the pipes (when horizontal) plus the static pressure when the discharge is higher than the supply. Table 6, column 1, gives the vertical rise in feet to any fixture up to 150 ft. in height; column 2, gives the static head in lb. pier sq. in. corre sponding with the vertical rise. The underlying principle involved in determining the proper pipe sizes for mains, risers and branches is to so regulate the size of these pipesthat they will carry the maximum amount of water required of them and absorb by friction and static head, all the pressure at the source and still deliver water at the fixture in sufficient quantity but at a pressure prac tically equalling zero or slightly above except that due to velocity of flow through the fixture. Table 1 gives the amount of water in gallons which should flow per minute for the number of fixtures indicated of each different type, together with the branch pipe size necessary to carry this amount of water with a pressure drop of 30 lb. per 100 ft. of run. The volume of water required per fixture is reduced as the number of fixtures in each group is increased, to take care of the factor of probable use. In estimating the pipe size for any part of a riser in a building of several stories, take 60 per cent of the water to be used on any floor and all floors above as determined from Table 1 and deduct 10 per cent for each floor above. This reduction in estimated amount is to take care of probable use. Thus, if 100 gal. are used on each floor of a 10-story building the size or pipe will be determined as in Table 2: Table 2. Water Risers for Manufacturing Buildings, Loft Buildings, Apartment Houses, Hotels G. P. M. G. P. M. Pipe Size with Drop per 100 Ft. Run 5 lb. 10 lb. 20 lb. 10 6 * 10 5 * 10 4 " 10 * 3 " 10 - 2 * 10 * 1 " 100 x 0.60 200 x 0.60 300 x 0.60 400 x 0.60 500 x 0.60 ' 600 x 0.60 700 x 0.60 800 x 0.60 . 900 x 0.60 1000 x 0.60 60% ~ 60 90% ~ 108 80% - 144 70% = 168 60% - 180 50% - 180 40% = 184 , 40% - 192 N 40% - 216 40% = 240 2m 2M' 3' 3M' 3M' 3 3H' 3H' w3X' 2' 234' 2>4' 3* 3* 3' 3' 3* 3' 3' 154' 2" 2H' 2}4' 2M' 2H' 2H' 2H' 2>$" Note.--For residences, use Table 1, and for the main supply use 25 per cent of total of gallons used by fixtures and then take pipe size from Table 5 on a basis of 10 lb. pressure drop per 100 ft. or less if water supply pressure is less than 50 lb. The pressure drop of 30 -lb. per 100 ft. of run will give satisfactory results for branches on the top floor but a higher pressure drop can be used on floors below corresponding with the pressures as given in Table 5 which show that for a building 100 ft. in height, a pressure drop of 100 lb. can be used on the fixture lowest branches and that for a building 50 ft. in height, a pressure drop of 52 lb. can be used on the lowest fixture branches; Table 1, however, can be used with safety on any of the floors 148 Chapter VI--Piping for Water Supply Systems but will give pipe sizes larger than necessary for the lower floors in a very tall building. Table 5 gives the amount of water in gallons which may be passed ^through pipes of M in. to 4 in. diameter with pressure drop from 5 lb. to 150 lb. per 100 ft. of run. This table may be used in sizing horizontal and vertical mains. For example, if the water main pressure available is known, say 90 lb., and the horizontal run from water main to vertical riser is 100 ft., and % the vertical riser is 100 ft. to'top branch; it will require 43.31 lb. for ` static head (see Table 6), and 15 lb. pressure at a minimum should be allowed for the uppermost fixture or a total of 58.31 lb. which would leave available for friction 90 -- 53.31 = 16.69 for friction in 200 ft. run, or 8.34 lb. per 100 ft. The main can thus be sized from the 7 lb. pressure drop of Table 5. Table 3. Apartment House Supply Risers Based upon One, Two, and Three Baths per Apartment One (l) Bath Apartment 1 bath 1 W. C. 1 sink 1 lav. 15 gal. 8 gal. 4 gal. 4 gal. 31 gals. 50% demand--15 gals, per mm. Top Floor 15 gal. Next 28 " 38 " 51 " " 60 a " 67 " " 71 78 a " 81 " " 83 a ** " " 85 " Riser mm 2". 2" 2" 2* 2" 2" 2* 2' 2" Two (2) Bath Apartment 2 baths 2 W. C. 1 sink 2 lavs. 24 gal. 14 gal. 4 gal. 6 gal. Three (3) Bath Apartment 3 baths '3 W. C. 1 sink 3 lays. 30 gal. 18 gal. 4 gal. 9 gal. 48 gals. 40%--20 gals. per min. 40%--24 gals per min. 20 gal. 38 " 54 " 68 " 80 90 " 98 " 104 " 108 " 110 " 110 " .110 " Riser IK' 1w 2' 2' 2' 2' 2 K' 2K' 2K' 2K' 2K' 2K' . 24 gal. 43 " 64 " 82 " 96 " 108 " 117 " 124 " 134 " 143 " 143 " 143 " Riser IK' 2" 2" 2 2K' 2'K" 2 yy 2K' 2W 2K" 2K' 2K' Note.1--:The pipe sizes are based branch for each Apartment should upon a be not drop of 10 less than lb. water in. pressure for each 100 ft. run. The size of Eoeample What is the riser size needed for a six-story apartment house having; one bath for each apartment? Table 3 gives 2 in. diameter for all from four to twelve stories with IK in. to supply the top floor and next to top and 1in. for floor below. What is the size of riser needed for a twelve-story apartment house with three baths to each apartment? Table 3 gives 2in. for all floors up to eighth floor, 2 in. for ninth, tenth and eleventh, and IK in. for top floor. What is the riser size for a two bath apartment six stories high? ,, T?ble 3 gives 2 in. for the first four floors with iy2 in. at fifth floor and IK in. on the top floor. 149 S