It's almost always an air leak.

It’s almost always an air leak.

A pump that hums but won’t push water has lost its prime, which means air is getting in somewhere before the water reaches the impeller. Don’t start taking apart the motor or replacing seals yet — nine times out of ten it’s something simple.

First, check the skimmer basket and pump basket for debris. If they’re clean, look at the pump lid O-ring. A cracked, dried, or misaligned O-ring sucks air like a straw. Lube it with silicone pool grease and reseat the lid. Next, make sure the water level in the pool is high enough to feed the skimmer — if it’s below the skimmer opening, the pump just sucks air.

If that doesn’t work, you likely have a tiny leak on the suction side: a cracked pipe, a loose fitting, or a bad gasket on a valve. Listen for a hissing sound near the pump when it’s running. Or spray shaving cream around joints and watch for it to get sucked in. That’s your spot.

Don’t let the pump run dry for more than a couple minutes — it can melt the impeller or damage the motor seal. Turn it off, fix the leak, and then re-prime by filling the pump basket with water before restarting.