70 MISC. PUBLICATION 4 3 4, U. S. DEPARTMENT OF AGRICULTURE 



Discharge in pipes is cut down by friction against the walls of the 

 pipes, or loss of head, which is usually expressed in feet per 100 feet of 

 pipe. Head means the amount of vertical fall in feet between the 

 entrance and discharge ends. In addition to the head caused by 

 vertical fall in the pipe, there is the head caused by the pressure of 

 water in the main or at the pump. This pressure on the pipe is mea- 

 sured in pounds per square inch, which can be expressed in feet of 

 head by multiplying by 2.31. This figure added to the total vertical 

 fall in feet in the pipe gives the total head in feet at the discharge end 

 of the pipe. 



Example: Suppose a pipe line is to be laid from the main pipe E 

 in a city water system to the nursery at D. 



Length of pipe E to D= 1,000 feet. 



Vertical fall from E to D=Head fall in pipe= 10 feet. 



Pressure in main pipe at £J=30 pounds per square inch. 



Head feet in pipe at E= 2.31X30= 69 feet. 



Total head feet at £=69+10=79 feet. 



If the nurseryman needs a discharge of 50 gallons per minute at D 

 and has 1,000 feet of 2-inch pipe which he wants to use, will the 2-inch 

 pipe be large enough? 



Table 18. — Friction of water in pipes — loss of head in feet due to friction, per 100 

 feet of 15-year-old ordinary iron pipe 



Discharge 

 (gallons 



per 

 minute) 



J-3-inch 

 pipe 



%-inch 

 pipe 



1-inch 

 pipe 



134 -inch 

 pipe 



1 H-inch 

 pipe 



2-inch 

 pipe 



2V-i -inch 

 pipe 



3-inch 

 pipe 



4-inch 

 pipe 



5-inch 

 pipe 



6-inch 

 pipe 



8-inch 

 pipe 



1 



2.1 

 7.4 

 15.8 

 27.0 

 41.0 

 147.0 

























2 



1.9 



4.1 

 7.0 

 10.5 

 38.0 

 80.0 

 136.0 























3 



1.26 



2.14 

 3.25 

 11.7 

 25.0 

 42.0 

 64.0 

 89.0 

 119.0 

 152.0 





















4 



0.57 

 .84 

 3.05 

 6.50 

 11.1 

 16.6 

 23.5 

 31.2 

 40.0 

 50.0 

 60 

 113 



0.26 



.40 



1.43 



3.0 



5.2 



7.8 



11.0 



14.7 



18.8 



23.2 



28.4 



53.0 



60.0 



102 



143 

















5 

















10 



0.50 

 1.08 

 1.82 

 2.73 

 3.84 

 5.1 

 6.6 

 8.2 

 9.9 

 18.4 

 20.9 

 35.8 

 50.0 

 54 

 76 

 102 

 129 



0.17 

 .36 

 .61 

 .92 

 1.29 

 1.72 

 2.20 

 2.80 

 3.32 

 6.21 

 7.1 

 12.0 

 16.8 

 18.2 

 25.5 

 33.8 

 43.1 

 54.3 

 66 



0.07 



.15 



.25 



.38 



.54 



.71 



.91 



1.15 



1.38 



2.57 



3.05 



4.96 



7.0 



7.6 



10.5 



14.0 



17.8 



22.3 



27.2 



31.3 



32.5 



38.0 











15 











20 













25 













30 









35 















40 







0.22 



.28 



.34 



.63 



.73 



1.22 



1.71 



1.86 



2.55 



3.44 



4.40 



5.45 



6.72 



7.70 



7.90 



9.30 



12.32 



16.00 



19.80 



22.40 



22.96 



24.00 









45 













50 















70 









0.21 



.24 



.41 



.58 



.64 



.88 



1.18 



1.48 



1.86 



2.24 



2.60 



2.72 



3.14 



4.19 



5.40 



6.70 



7.22 



7.42 



8.12 



9.60 



11.30 



13.20 



15.10 



17.20 







75 













100 











0.14 



.25 



.28 



.32 



.48 



.62 



.74 



.92 



1.13 



1.15 



1.29 



1.75 



2.21 



2.65 



2.90 



2.95 



3.30 



3.93 



4.70 



5.40 



6.20 



7.00 



8.00 



8.95 



10.11 



10.80 



12.04 



13.30 



14.31 



15.60 



16.69 



18.50 





120 













125 













150 















175 















200 















225 















250 















0.22 



270 















.25 



275 

















.27 



300 

















.32 



350 

















.42 



400 



















.54 



450 



















.68 



470 



















.75 



475 



















.76 



500 



















.82 



550 



















.97 



600 





















1. 14 



650- 





















1.34 



700 . 





















1.54 



750. - 





















1.74 



800 





















1.97 



850 























2.28 



900 























2.46 



950 - 























2.87 



1,000 























3.02 



1,050 























3.21 



1,100.- 























3.51 



1,150 























3.84 



1,200 























4. 15 



1,250 _ 























4.45 



1.500 























6.27 



