PUMPING MACHINERY 



alone. Often as much as one-half or even more of the 

 power is required for this purpose. A common rule in 

 use to determine approximately the power required to 

 operate a farm pump is that one horse power is required 

 to lift 30 gallons 100 feet per minute. From this rule it 

 is easy to calculate for different capacities at more or less 

 head. The rule assumes a mechanical efficiency of 68 

 per cent on the part of the pump. 



The friction of water flowing in pipes is also very 

 great. The loss of head due to friction is proportional 

 to the length of the pipe and varies about as the square 

 of the velocity of the flow. It is greatly increased by 

 angles, valves, roughness, and obstructions in the pipe. 



The following table given by Henry N. Ogden indi- 

 cates the loss of head due to friction in pipes : 



LOSS OF HEAD DUE TO FRICTION* 



The importance of choosing a pipe of sufficient size 

 for the flow per minute and the length of pipe is shown 

 by this table. For instance, suppose it is desired to de- 

 liver seven gallons a minute at a distance of 500 feet. 

 The J/2-inch pipe would require an impractical head of 



"The Installation of Farm Water Supplies Cyclopedia of American Agri- 

 cuiture, Vol. I., page 294. 



