Raise the water level first.

Yes, that’s almost always the fix.

If your pool skimmer is sucking air, the water level is probably too low. The skimmer needs water covering its opening to pull water instead of air. Bump it up to at least halfway up the skimmer mouth — you’ll hear the air noise stop almost immediately.

If that doesn’t work, check the obvious stuff: is the skimmer basket clean? A clogged basket restricts flow, which can cause cavitation. Is the weir door (the flap inside) stuck open? That lets air in. Are the pump lid O-ring and drain plugs tight? A tiny air leak on the suction side will whistle like crazy.

If you’ve checked all that and still have air, you might have a crack in the suction line underground. That’s a job for a pro, but don’t jump there before checking the cheap fixes.

Simple before expensive.