ZIMSEC O Level Combined Science Notes: Pumps: Lift pump

  • It has a cylinder
  • A piston
  • Two valves and
  • a spout
  • They make use of atmospheric pressure which forces fluid (water) into the pump through valves
  • Valves allow fluid to only flow in one direction
  • At any given point there is one valve open and another closed


Lift pump diagram.

Lift pump diagram.

  • During the upstroke the piston moves up
  • Atmospheric pressure puts pressure on the water in the well
  • The water then pushes against valve B forcing it open
  • Water enters the cylinder
  • Valve A is closed during this cycle
  • During the downstroke the piston moves down
  • Valve B is closed by the force of water
  • The pressure of the water forces Valve A to open
  • Water then enters the area above Valve A
  • And flows out through the spout


  • It is light, cheap and easy to assemble, operate and repair
  • No lubrication is required as water is used to lubricate the pump


  • Can only lift water in wells less than 9m deep.
  • They only deliver water during the upstroke
  • They require priming before use

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