Priming a Jet Pump

Priming a Jet Pump

Priming a Jet Pump

Jet pumps are considered one of the two most popular types of pumps used for private well systems and low flow irrigation applications. This solution is popular in areas with high water tables and warm climates. The pump itself is mounted above ground and typically used to lift water out of the ground through a suction pipe, which allows it to use centrifugal operation and ejection. In order to efficiently get water from point A to B, it takes the help of many jet pump parts. To ensure all these parts perform properly, a priming procedure is performed.

Priming a jet pump simply means preparing it for delivering water. All jet pumps need to be primed upon initial installation and, under normal use, they will not need to be re-primed again. The act of priming refers to filling the pump with water and forcing the water through the suction pipe to remove the air, which is necessary to create the pressure needed for the pump to begin working. The end result for priming a jet pump is to have the entire pump casing, including the suction pipe, completely full of water with no trapped air.

An air leak in the suction line will cause the pump to quit pumping. This is sometimes referred to as ‘losing its prime.’ A procedure can be performed in order to re-prime, which will make the entire casing and suction full of water.  A jet pump may lose its prime for the following reasons:

  • Possible leaks in suction piping, foot valve, or air volume control connections
  • Water may be drawing down below foot valve, causing pump to take excessive air
  • If deep well installation, regulating valve may be set for insufficient pressure to operate the jet
  • If single pipe installation, water may be leaking between packer assembly and well casing. Water may be leaking back to the soil through worn out or defective well casing.
  • Check valve not working

When priming the pump, disconnect the power supply for safety reasons and adhere to the following steps. Please make sure to never turn on a pump when it is empty as this can cause serious damage to the pump:

  1. Locate the priming plug on your pump and unfasten this plug
  2. Fill the entire pump and suction pipe with clean water
  3. Loosely refasten the priming plug
  4. Turn on the pump to check it’s working. It should run until its cycle is finished and then turn it off by itself. If it does, you can tighten up your priming plug.

    If your jet pump won’t prime, repeat steps 1-4. Some pumps take more than one priming session in order to remove all the air from the system.

    If your pump still isn’t priming, check the entire system for any signs of damage or leaks.

    If the priming procedure has already been performed and the results aren’t successful, click here to view the jet pump troubleshooting section of A.Y. McDonald’s pump catalog.


For additional tips and tricks to priming a jet pump or to learn more about the functionalities of the pump itself, reach out to A.Y. McDonald by calling our Customer Service Department at 1-800-292-2737, filling out a Contact Us form on, or taking the ‘Priming a Jet Pump’ AYU course.