82 



WATER IN THE HOME 



in the cistern. When the piston is lowered the valve in 

 the piston opens, thus allowing the water to run into the 

 space above the piston. On the next upward stroke of 

 the piston this water which is held above is lifted still 

 higher in the tube until eventually 

 it flows out of the pump. This 

 pump, known as the lift pump, will 

 only raise water to a height of 

 about 33 feet because the weight 

 of the air, which presses down with 

 a force of fifteen pounds to the 

 square inch upon the surface of the 

 water in the cistern, can balance a 

 column of water only 33 feet high. 

 In practice the lift pump will rarely 

 lift water more than 28 feet because 

 of leakage around the piston and 

 valves. 



If we wish to force water above 

 twenty-eight feet we use a force 

 pump. This is illustrated in the 

 accompanying diagram. Study it 

 carefully and explain why we are 

 able to raise water higher by this method than by the lift 

 pump. Chamber A holds air which may be compressed 

 in order to give a continuous flow of water. Can you ex- 

 plain how it does this? 



The pneumatic tank system. In some houses a supply 

 system by which water can be piped and sent to all parts 

 of the house is used. This can be done through the use of 

 a pneumatic tank. (See illustration on page 83.) Water is 

 forced into the tank and the confined air above it is com- 



The force pump. 



