THE FLOW OF WATER IN CONCRETE PIPE. 55 



will be 1.7X2.8 = 4.76 feet. In addition to this the loss of head 



52 

 necessary to create the velocity of 5 feet per second is ^"1 = 0.4 



foot. Assuming the entry head as one-half the velocity head gives an 

 additional loss of 0.2 foot. Since for most installations there is but 

 little or no recovery of velocity head at the outlet, it may be assumed 

 that the total loss of head will approximate 4.8+0.4+0.2=5.4 feet. 

 If it is not feasible to sacrifice 5.4 feet a lower maximum velocity may 

 be assumed and the above process repeated, this of course resulting 

 in a larger pipe. If elevation is of little moment, that is, if more grade 

 may be sacrificed, then a higher velocity may be assumed and a 

 smaller pipe used. 



The same results may be obtained by interpolating in Table 8. 



(2) An orchardist wishes to convey the output of a 5-inch centri- 

 fugal pump, rated at 700 gallons per minute, from a standpipe near 

 the well to the high corner of his orchard which is 5 feet higher than 

 the land at the standpipe, and 1,370 feet distant along the line the 

 pipe must follow. The owner wishes to use 12-inch pipe made by the 

 dry-mix process. How high must the standpipe be to deliver the 

 water at the high corner of the orchard with a pressure head of 2 feet 

 still available to insure a free discharge ? To provide for an assured 

 capacity of the line, for a slight undersize in the pipe, and a slight 

 overload for the pump, we will figure on 15 per cent more than 70(3 

 gallons per minute or 700 + 105 = 805 gallons per minute. In column 

 4, Table 6, we find the item 809 as nearest to 805. This is close enough 

 for our computations. Opposite 809 in the columns under a 12-inch 

 pipe we find the velocity V, of such a flow in a 12-inch pipe will 

 be 2.29 feet per second and the friction head for 1,000 feet of pipe, 

 H, will be 2.44 feet. Since our pipe will be 1,370 feet long, this 

 friction head will be 1.37x2.44 = 3.34 feet. A small amount of fall 

 is also necessary in order to generate the velocity of 2.29 feet per 

 second and to get the water from the standpipe into the flow line. 

 In Table 5, page 52, we find that a velocity of 2.4 feet per second 

 requires a head (fall) of 0.135 foot, according to column 4. Thus 

 the following items enter into the total height of our standpipe : 



Feet. 



Difference in elevation of the ground surface 5. 00 



Reserve pressure head at outlet 2. 00 



Friction loss in 1,370 feet of 12-inch pipe for 809 G. P. M 3. 34 



Head to generate velocity and get water into the pipe 13 



Total 10. 47 



So a standpipe 11 \ or 12 feet high, measured from the ground 

 surface, will be sufficient to insure the flow and have some elevation 

 in reserve for "freeboard" and surging. 



