My Pump Is Not Fully Priming, What Could Be the Cause?
Work through these checks in order, from the quickest to the most involved
Before you start
Switch the pump off while you work through these checks. Hayward's pump manuals state that a pump should never be run dry, that running it dry can damage the seals and cause leakage and flooding, and that it voids the warranty. A pump that will not prime is drawing little or no water, so leaving it running while you troubleshoot is how a priming problem turns into a pump replacement.
Fill the strainer housing with water before you start the motor for each attempt.
Work through these checks in order
Start at the top. Each check is quicker and safer than the one below it.
| Possible cause | How to check | What to do |
|---|---|---|
| Low water level | Look at where the water sits against the skimmer opening | If the water is at or below the opening, the pump is drawing air. Add water and try again |
| A closed or partly closed valve | Check every suction and discharge valve on the system | Hayward specifies that all suction and discharge valves must be open when starting the circulation system. Open them fully |
| Empty strainer housing | Look through the strainer cover | Fill the strainer housing with water before starting the motor |
| Blocked skimmer or pump basket | Remove and inspect both baskets | Clear out any debris and refit them |
| Dirty filter | Check when the filter was last serviced | Backwash a sand or DE filter, or clean the cartridge. To rule the filter out, try bypassing it on recirculate or removing the cartridge |
| Air leak on the suction side | Check the pump lid and its o-ring, the drain plugs, the unions on the suction side, and the valve stems | Tighten or replace whatever is letting air in. An air leak is one of the most likely reasons a pump primes partially rather than not at all |
| Clogged impeller | Requires opening the pump. See the section below before you do this | Follow the steps in the next section |
Opening the pump to check the impeller
The impeller is the part inside the pump connected to the motor that moves the water. It clogs from time to time with small debris. To inspect it you will need to open the pump to see inside the housing, or volute.
Before you open the pump, Hayward's manuals set out four steps:
- Stop the pump.
- Disconnect the pump from the main power supply completely. Turn the power off at the breaker, not just at the timer or switch.
- Close the valves in the suction and outlet pipes.
- Release all pressure from the pump and piping using the filter's manual air relief valve.
Pool circulation systems run under hazardous pressure during start-up, during normal operation, and after the pump shuts off. Hayward warns that skipping these steps can cause the pump housing and cover to separate violently, which can result in property damage, severe personal injury, or death.
These precautions are from Hayward's pump manuals. If your pump is another brand, follow the safety instructions in your own manual.
Check your pump's manual for a parts diagram showing how the pump comes apart.
If none of this works
If you have worked through every check and the pump still will not hold a prime, stop rather than continuing to run it. Hayward specifies that shaft seal replacement should only be attempted by qualified personnel, and a pump that will not prime after all of the above usually needs diagnosing in person.
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