What Why How To Prime A Centrifugal Pump

June 13, 2021

Priming a pump is probably the first and one of the most important thing you should do before operating it.

Not priming a pump or not doing it properly makes up 80 percent of centrifugal pump problems. While centrifugal pumps are relatively inexpensive, the downtime of your system due to a malfunctioning pump might be costly.


Priming simply means preparing or getting something ready for operation.

For a centrifugal pump to work properly, you need to remove the air and fill it up with water.

When everything is right, a standard (non-self-priming) centrifugal pump looks like this.

The pump will resume operation once the air is removed.

Both diagrams above courtesy of Pumpstoreusa.com

Most centrifugal pumps are incapable of pumping vapours or gases and continuously doing so will damage the pump impeller.


A self-priming centrifugal pump is able to overcome the problem of air binding by mixing air with water. After it gets rid of the air, the pump will continue to move water like a standard centrifugal pump.

Self-priming pumps can’t operate without water.

Primed Meaning

The air or air pocket from the pump and pump line or pump tubing has been removed. The pump is now full of water and ready to use.

Self-Priming Pump Operation

Priming Pump Basics

Failure to Prime


Different pumps and different system setups require different steps to prime. Refer to your pump manual for more information.

When The Suction Supply is Above The Pump

  1. Discharge isolation valve
  2. Check the valve
  3. Suction isolation valve

The following are the steps to priming the pump:

  • Slowly open the suction isolation valve.
  • Open the air vents on the suction and discharge piping until the pumped fluid flows out.
  • Close the air vents.

When The Suction Supply is Below The Pump

  1. Discharge isolation valve
  2. Shutoff valve
  3. from outside supply.
  4. Foot valve
  5. Check valve

Consider using a foot valve and an outside source of liquid in order to prime the pump.

  • Close the discharge isolation valve.
  • Open the air vent valves in the casing.
  • Open the valve in the outside supply line until only liquid escapes from the vent valves.
  • Close the vent valves.
  • Close the outside supply line.

Courtesy of Enggcyclopedia.com.

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