USE OF CONCRETE PIPE IN IRRIGATION. 



25 



carry about 20 per cent more water than shown by table, especially 

 where there is danger of any clogging by debris, or pipe is very rough. 



Table gives the carrying capacities of concrete pipe in miner's inches computed 

 to the nearest 5 miner's inches. 1 







[Fall 



in feet per 100 feet.] 









Diameter of pipe. 



0.1 



0.2 



0.3 



0.4 



0.5 



1.0 2.5 



5.0 





Miner's 



inches. 



10 



20 



35 



60 



85 



120 



160 



225 



275 



350 



650 



Miner's 



inches. 



10 



25 



50 



80 



120 



170 



230 



310 



400 



500 



900 



Miner's 



inches. 



15 



35 



60 



110 



150 



210 



285 



380 



485 



620 



1,100 



Miner's 



inches. 



20 



40 



70 



115 



170 



235 



330 



435 



525 



710 



1,275 



Miner's 



inches. 



20 



45 



80 



120 



200 



275 



450 



500 



625 



800 



1,425 



Miner's 



inches. 



30 



60 



110 



180 



275 



400 



550 



700 



900 



1,150 



Miner's 



inches. 



45 



85 



180 



275 



400 



600 



825 



1,100 



1,400 



Miner's 

 inches. 

 60 : 





140 





250 













































1 One miner's inch is here equivalent to the one-fiftieth part of a second-foot and is nearly equal to 9 

 gallons per minute. 



Engineers and pipe contractors will have no trouble in interpret- 

 ing the above table, but for the convenience of irrigators without 

 engineering experience, a few examples will be given to enable them 

 to estimate sizes of pipe for various conditions. 



The retarding influence to flow of water known as friction is com- 

 mon to all pipes, the intensity of the friction increasing with the ve- 

 locity of the water and the roughness of the pipe. If the pipe is laid 

 down grade the fall may be sufficient to overcome friction. When the 

 water is pumped if the fall is not enough to carry the desired quantity 

 then the water will rise in the standpipe at the entrance until there is 

 sufficient head to force the water through. Of course if the stand is 

 not high enough water will spill over the top. If the pipe runs up 

 hill, when water is pumped, the delivery box or relief stand at the 

 pump end must be high enough to overcome the difference in eleva- 

 tion between the entrance and outlet of the pipe, plus the head re- 

 quired to overcome friction in the pipe. In practice such standpipes 

 should not be high enough to develop unsafe pressures on the pipe. 



Example 1. 



Assume that an irrigator has acquired the right to the use of 200 

 miner's inches of water and wishes to install a pipe to carry this 

 amount to his farm, a distance of 2,000 feet. If levels show there is 

 a total fall of 6 feet between entrance and outlet, he will have a fall of 

 0.3 foot per 100 feet. From the table under vertical column of 0.3 

 (fall per 100 feet) it is seen that a 16-inch pipe will carry 210 miner's 

 inches. If he can fill the standpipe at entrance 4 feet deep, he will 

 have 4 feet additional head on the pipe, or a total head of 10 feet (in- 

 cluding fall). This gives him 0.5 foot fall per 100 feet. The table 

 3445°— 21 4 



