How to prime a swimming pool pump manually and why it de-primes.

Knowing how to prime a pool pump correctly is essential for the filtration system to function normally. When a pump is not primed, it does not draw water, loses flow, makes noise and may overheat or stop due to thermal protection. If the problem recurs, it usually indicates air ingress, poor sealing or pump wear.

As professionals in maintenance and sale of pool pumps, we explain how to perform manual priming, what changes when the pump is elevated, how to purge the installation and why a pool pump is de-primed. We also tell you when to stop insisting and replace the pump with a new one.

How to Prime a Pool Pump Manually

Priming a pool pump consists of completely filling the pump body and suction pipe with water to remove air. Centrifugal pumps do not draw air and need water to generate the vacuum that moves the circuit.

To prime a pool pump professionally, follow the steps below:

1. Turn off the pump and turn off the power. Never handle the prefilter cover while the pump is running.
2. Open the prefilter cover. Slowly loosen to release pressure. You can remove the basket if necessary.
3. Completely fill the prefilter with water. Use a hose or bucket to do this, filling to the brim. This step is key to manual priming.
4. Check and lubricate the o-ring. Clean the cap seat and lubricate the o-ring with neutral petroleum jelly to ensure tightness.
5. Close the lid properly. Tighten firmly, but without forcing.
6. Opens suction valves. The Skimmer and/or bottom must be fully open.
7. Start the pump. Watch the prefilter, to make sure it fills completely in seconds. The return must recover pressure progressively.
8. Additional purge (if applicable). If you have a sand or glass filter, open the filter trap until air-free water comes out and close it.

How to Prime an Aboveground Pool Pump

When the pump is above the water level, priming requires more attention because gravity does not help.

Our professional recommendations are:

• Make sure that all suction connections are perfectly sealed.
• Fill the prefilter several times if necessary.
• Keep the hose inside the prefilter while filling to draw in air.
• Starts and stops briefly if necessary until the flow rate stabilizes (without forcing).

Why does a pool pump break down?

If the pump breaks down, the problem is not priming: it is air ingress or leakage. The most common causes are:

• Dry, damaged or dirty prefilter cover o-ring.
• Lid not properly closed or seat deformed.
• Loose drain plug.
• Fittings or threaded joints with deteriorated Teflon.
• Valves with clearances.
• Suction pipe with microcracks.
• Low water level (below the Skimmer).
• Deteriorated motor seal (in old pumps).

Signs that will indicate de-priming are constant bubbles in the prefilter, the prefilter not filling completely, hollow noise, gurgling and loss of pressure after switching off or on.

Common errors that cause recurrent deboning

• Do not lubricate the prefilter o-ring.
• Partially close suction valves.
• Start without filling the prefilter.
• Ignore small leaks “that seem insignificant”.
• Use of inadequate grease in o-rings.

When priming a swimming pool pump is not enough

Priming does not solve the problem if the pump is de-primed every day, there are persistent internal or external leaks, the pump body is deformed, the motor seal is damaged or the pump is old and has lost its tightness.

In these cases, insisting only leads to overheating and major failures. It would be time to replace the pump with a new one. At PoolComet we recommend the ESPA range of Swimming Pool filtration pumps. Specifically:

• Silen I or Nox for small pools.
• Silen S or Silen S2 for medium to large pools.
• NoxSalt for pools with salt chlorination or high salinity.

Frequently asked questions about priming and de-priming pool pumps

How to prime a pool pump manually?

Turn off the pump, open the prefilter, fill it completely with water, check and lubricate the o-ring, close it tightly and start with open valves. Purge the filter if necessary.

Why is a swimming pool pump de-primed?

Because air enters the suction or there is a leak (o-ring, cover, fittings, low level). Priming is not the cause; it is the symptom.

How to prime an aboveground pool pump?

It ensures total sealing, fills the prefilter several times and purges the air. If it is often unbrazed, check suction and joints.

Is it normal to see bubbles on start-up?

Yes, for a few seconds. If they continue, it indicates persistent air and the system should be checked.

Can I purge the pump when the pool is empty?

No. The pump should not run without water; this will damage the seal and the motor.

Does an old pump de-boil more?

Yes. Over the years, o-rings and body become less tight, and priming becomes unstable.