When a pool pump loses prime it runs but cannot pull water, and the fix is to clear the obstruction, refill the pump, and let it re-establish suction. The usual causes are a low water level below the skimmer, a clogged pump or skimmer basket, or air sneaking in through the pump lid or a fitting. Turn the pump off, clean the baskets, fill the pump housing with water, seal the lid, and restart. Running a pump dry for long can burn out the motor seal, so do not let it grind away without water.
What you'll need
- A garden hose
- A bucket
- Silicone-based lubricant for the lid o-ring
- A screwdriver
- Towels
Recommended parts & supplies
- Pump lid o-ring / gasket — a dried-out lid seal is a top cause of lost prime
- Silicone o-ring lubricant — keeps the lid seal airtight
- Replacement pump basket — a cracked basket lets debris jam the impeller
- PVC / Teflon thread seal tape — reseals leaking threaded fittings on the pad
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Step by step
- 1
Turn the pump off and check the water level
Shut the pump off first — running it dry damages the seal. Then look at your pool water level. It should be about halfway up the skimmer opening. If it has dropped below the skimmer mouth, the pump is sucking air instead of water; top the pool off with a hose before doing anything else.
- 2
Empty the skimmer and pump baskets
Pull the skimmer basket and clear out leaves and debris. Then, at the pump, twist off the clear lid and lift out the pump strainer basket and clean it too. A basket packed with debris chokes the flow and is one of the most common reasons a pump loses prime. Check the basket for cracks while it is out.
- 3
Inspect and lubricate the pump lid o-ring
Find the rubber o-ring that seals the clear pump lid. If it is dry, cracked, or flattened, air leaks in and the pump cannot hold prime. Wipe it clean and apply a thin coat of silicone lubricant, or replace it if it is worn. This one seal is behind a surprising number of suction problems.
- 4
Fill the pump housing with water
With the basket back in place, fill the pump housing to the top with water from a hose. This gives the pump the water it needs to grab prime instead of spinning against air. Then set the lid back on and hand-tighten it snugly — do not over-crank it, which distorts the o-ring.
- 5
Open the air-relief valve and restart
If your filter has an air-relief valve on top, open it. Set any multiport valve to FILTER, then turn the pump on. You will see air and water sputter through the clear lid at first. Within a minute or two the pump should pull a steady, air-free stream of water and the flow should settle. Close the air-relief valve once water sprays out.
- 6
If it still will not prime, hunt for an air leak
If it keeps sucking air after a minute or two, you likely have an air leak on the suction side. With the pump running, look for a fitting between the skimmer and pump that is not tight, or hairline cracks in the plumbing. A quick test: smear a little pump lubricant on a suspect joint — if the pump smooths out, that joint is drawing air and needs resealing.
When to call a pro
Call a pro if the pump will not hold prime after you have refilled it, cleaned the baskets, and sealed the lid — that usually means a suction-side leak underground, a failing pump impeller, or a bad shaft seal that needs the pump opened up. Anything electrical, like a pump that hums but will not spin, a tripping breaker, or replacing a capacitor or motor, is 240-volt work best left to a licensed tech. And if the pump has been running dry and smells hot, shut it off and get it checked before the motor is ruined.
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How to Prime a Pool Pump That Lost Suction — FAQ
Why is my pool pump not pulling water?
Is it bad to run a pool pump with no water?
How do I know if my pool pump has an air leak?
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