5 Reasons Your Pool Pump Keeps Losing Prime

Loose or worn pump lid o-ring The lid o-ring is the most common cause. Lube it with pool silicone or replace it if it is flattened or cracked.

Crack in the pump housing A small crack in the housing lets air in but not water out. Inspect the housing carefully for hairline fractures.

Leak in suction-side plumbing Air gets sucked in through tiny leaks in pipes or fittings between the skimmer and pump. Spray a garden hose on suspected joints; if the pump primes, you found the leak.

Bad multiport valve gasket Old multiport valves on the filter can let air in if the internal gasket is shot. This is less common but worth checking.

Running the pump with air in the system Ignoring a suction-side air leak will burn out the motor and ruin filter performance. Fix the leak immediately.