Air leaks are the main reason your pool pump loses prime

Yes, a pump losing prime is almost always an air leak on the suction side.

The pump is trying to pull water from the pool, but air is sneaking in before the water gets to the impeller. That breaks the vacuum, and you lose prime. Common culprits: the pump lid O-ring is dried out or dirty, the drain plug isn’t tight, or the shaft seal is failing. Sometimes the water level in the pool dropped below the skimmer, and the pump is sucking air instead.

To troubleshoot, start simple. Turn off the pump. Open the pump lid, clean the O-ring, apply some silicone lube, and reseat it firmly. Check the drain plug. Look for any wet spots or corrosion on the pump body that suggest a leaking shaft seal. While running, spray the plumbing joints with a hose — if the pump suddenly primes, you found the leak (water temporarily seals it).

If everything looks good, check the pool water level. If it’s below the skimmer, the pump can’t get water. Raise the level and re-prime.

Don’t ignore it. Running a pump dry overheats the motor and damages the impeller. Fix it this weekend.