Suction Pump. 647 



The piston is usually worked by a simple lever in the 

 form of the pump handle and the water is discharged 

 through the spout in the pump-head near the level of the 

 ground. 



693. Size of Piston. The size of piston which should be 

 used in a well depends upon the Light to which the water 

 must be lifted and the power which is available to work 

 the pump. In working a common pump a man can com- 

 fortably exert a pressure of only 15 to 20 pounds upon the 

 pump handle and, as the power arm of this lever is only 5 

 to 7 times that of the weight arm, the pressure exerted 

 by the water to be lifted at one stroke cannot much exceed 

 75 to 100 pounds. Water at ordinary well temperature 

 exerts a pressure of .43 pounds per square inch for each 

 foot of depth. This being true, whenever the piston is 

 called upon to lift water through a hight of 40 feet the 

 pressure on the piston would be at the rate of 



40 X 43 = 17.2 Ibs. per sq.jn. 



A 2-inch piston has an area of 3.14 square inches, a 2.5 

 inch piston 4.9 square inches, a 3-inch piston 7.07 and 

 a 3.5-inch piston 9.62 square inches, so that in lifting 

 water through 40 feet with each one of these pistons the 

 force required to be applied to the piston rod would Lave 

 to be 



For the 2 inch piston 54.01 Ibs. 



For the 2. 5 inch piston 81.28 Jbs. 



For the 3 inch piston 121.60 Ibs. 



For the 3. 5 inch piston 165.48 Ibs. 



It will be clear from these figures that for ordinary hand 

 pumping a 2 to 2.5-inch piston is as large as can be com- 

 fortably worked in a well where the lift must equal 40 

 feet If the well has such a depth that the water must be 

 lifted 100 feet the 2-inch piston would sustain a pressure 

 of 135 pounds and hence would be larger than could be 

 comfortably worked in such a well. 



