80 percent of centrifugal pump problems are caused by not priming a pump or not doing it properly.

putting on gloves

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.

What is pump priming?

Priming simply means preparing or getting something ready for operation.

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

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

pump fully prime

When air gets into a standard (non-self-priming) centrifugal pump, the pump doesn’t work and looks like this:

pump airbound

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.

What about self-priming pumps?

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.

Self-Priming Pump Basics
Self-Priming Pump: Failure to Prime

How to prime a pump

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

pump prime supply above
Courtesy of Enggcyclopedia.com.

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

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 below the pump

pump prime supply below
Courtesy of Enggcyclopedia.com.

  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.