If your foot valve is leaking your pump may lose its prime between starts. ... Debris blocking the suction strainer or foot valve is the most common cause. A blockage in the intake line can cause the water in the pump casing to overheat and literally boil out of the casing causing the pump to lose prime.

Why is my pool pump losing prime overnight?

You most likely have very small leak in the backwash valve or filter can rubber seal. Air creaps in the filter dome overnight. Sometimes it is the cover on the pump strainer.

Why does it take so long for my pool pump to prime?

Most priming problems involve leaks in the suction side of the pump (between the pump and the pool) or clogged baskets. If you have a leak on the pressure side (after the pump), it does not affect prime. You just lose water.