What should I do if my pool skimmer is sucking air?

Raise the water level first — it’s almost always the fix. The skimmer needs water covering its opening to at least halfway up the skimmer mouth; the air noise will stop almost immediately. If that doesn’t work, check the skimmer basket for clogs, the weir door for sticking, and the pump lid O-ring and drain plugs for tightness. If all cheap fixes fail, you might have a cracked suction line, which requires a pro.