FLOW OF WATER THROUGH PIPES. 1 39 



Note. — Add one half the depth of dram at upper end =15 feet to 

 the fall for value of /. 



How many acres when the tile is laid on a grade of 10 foot per 100 

 feet? 

 .5 X 2.5 = 125 = ^. ^=5; 



/= I f 1,5 = 2.5; 

 / -f- 54^/ = 1027, 



^ ^^ = .00121 4/. 0012 1 = .0348 ; 48 4/.00121— 1.67 = V. 

 1027 



e r= 1.67 X .1964 ~ -32798 



.';27q88 

 Acres = ^ — = 31.23. 



Note. — Making/ = grade only, which should be used where the 

 soil is close. Acres = 20. 



To find the volume of water in cubic feet per second 

 which a tile drain will discharge, multiply the computed 

 velocity in feet per second for the diameter of tile re- 

 quired by the number given in column 3 of Table 2. 



Note. — To reduce cubic feet to gallons multiply by 7.48, 



Weight of I cubic foot of water ^%\ lbs. 



Weight of I gallon of water .8.35 lbs. 



Seconds in i hour 3600 



Seconds in 24 hours 86,400 



Number of cubic feet of water on i acre of land when covered i 

 inch deep 3630 



The Total Head or Fall that should be Used. — In 



considering the total fall of a main drain it is quite evi- 

 dent that the head which generates the flow is not in all 

 cases the difference in elevation of the two ends of the 

 line, but when supplied by a system of laterals which 

 have a greater rate of incline the velocity head will be 

 increased by the laterals. Also, if the soil is saturated 

 above the tile to nearly the surface, and the soil is free 

 and open, the main drain as well as the laterals will 



