Check the pump lid first.

Start by inspecting the pump lid gasket. Nine times out of ten, a lost prime is just a worn-out O-ring or a lid that wasn’t tightened evenly.

Air gets in, water falls back, prime disappears. Pop the lid, clean the gasket and the sealing surface, lube it with silicone pool lube, and re-tighten firmly by hand. If it’s cracked or flattened, replace it — a $5 part from any pool store.

Still losing prime? Then look at the water level in the skimmer (too low will suck air) or the drain plugs on the pump housing. But start with that lid. It’s almost always the lid.

Future you will thank you for keeping a spare O-ring in the garage.