AO Smith pool pump loses prime overnight and must be manually primed each day.

Safety First: Turn OFF power before working on plumbing or opening the pump.

• Inspect lid seal: Clean and lubricate the pump lid O-ring. Replace if it shows cracks or flattening.
• Check unions: Tighten suction-side unions by hand plus a small additional turn with a strap wrench if needed. Do not overtighten to the point of cracking.
• Look for leaks: With the pump running, use soapy water around joints and fittings on the suction side. Bubbles being sucked in indicate an air leak.
• Check valve function: If a suction-side check valve is installed, verify that it is oriented correctly and not stuck open. Replace if it does not hold water in the line when the pump is off.