Prime Pool Pump

My pool pump loses it’s prime at night when pool is off & has to re-prime when it comes back on the next day.  Is this a problem for the pump or is this normal?

The pool pump should hold the prime overnight if it is completely sealed. It sounds like you have a small leak somewhere. There could be a leak on the suction side or pressure side. The suction side is everything before the pump and the pump lid. Everything beyond the discharge side of the pump is the pressure side.

Suction side leaks will draw air when the pump is running and after the pump shuts off it could cause the water to drain. The most common place for a leak on the suction side is the pump lid because the o-ring needs to be lubricated or replaced. Other sources could include diverter valves, unions, and fittings.

A pressure-side leak is easier to detect. Water would drip from the source when the pump is running.