THE LIFT AND FORCE PUMP

The lift pump is used to raise water from wells. It consists of a piston in a barrel or cylinder. The piston head has a hole through it which can be closed by a upper valve . The second lower valve  closes the barrel at its base .

The following stages describe the working principle of the lift pump

1. When the piston moves downward the lower valve  closes and upper valve open .
2. When the piston moves upwards the upper valve  closes and pressure inside the barrel decreases and the lower valve  open, atmospheric pressure causes water to flow into space above lower valve
3. When the piston moves down again pressure increases, lower valve  closes and upper valve open thereby water enter above upper valve
4. On the next upward stroke valve upper valve closes and water is raised to the outlet pipe where it escape . At the same time atmospheric pressure forces water past lower valve 

Lift pump operates under atmospheric condition, therefore it can not lift water more than a height of 10m because atmospheric  pressure does not support a column of water more than 10m.

The Force Pump

When its require to lift water above 10m height , a force pump is used.

The main differences in the lift pump and force pump are:

1. The upper valve  comes below the piston in force pump 

The operation is as follow

As the piston moves up , atmospheric  pressure pushes water through lower valve  into the pump

When the piston moves down water is forced through upper valve and upward. The force pump can lift water to any height but this depends on the force used and the quality of the pump.

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