What is pump priming?

What is pump priming?

When the pump is in stopped condition casing is empty of the pump is only partially filled with water, rest of the available space is filled with air. 

This case is happening in negative suction pumps.


  1. ETP Pumps
  2. Water reservoir pumps

When the pump is started the water and air inside the pump will move together in the pump such that the density of resulting liquid is reduced, enough suction at impeller eye is not creates.

The air must be removed by filling the partially filled pump with water until all available space is filled with water. 

If we start pump with air inside discharge pressure varition will be found. This start up creates high vibration due to air bubbles impact on impeller.

This will result into pump internal erosion (damage, rough surface)

This air must be removed from casing by filling it from suction line till water came out from vent valve.

This process is called pump priming and it is done before the pump is started for any kind of operation.

Air starts moving out of the vent valve and when the liquid starts coming out of vent, the valve is closed. 

The liquid oozing out indicates that the interior of the pump is filled with liquid.

Self priming pump are those which don’t need manual priming. 

They mix the water and air and when that mixed water is removed from the system the pump starts operating.

Read more about "Centrifugal Pump" from Industrial Guide - Click here

Thanks for reading -  What is pump priming?
Naitik Patel
Industrial Guide

Share this blog with your friends from here 👇

Previous Post Next Post