Air in a pool filtration system is almost always a suction-side problem. Water flows from the pool to the pump under negative pressure — meaning the pump is pulling water toward it. Any gap, crack, or failed seal on that side of the pump lets air get sucked in instead. The symptoms show up at the filter and at the return jets, but the source is almost always between the pool and the pump inlet.
How to Tell You Have an Air Leak
- Bubbles shooting out of the return jets when the pump first starts
- Persistent fine bubbles from returns even after several minutes of running
- Pump basket not completely full of water — partial air pocket visible
- Pressure gauge needle bouncing or fluctuating instead of holding steady
- Pump losing prime intermittently
Where the Air Is Getting In
Don't Want to Deal With This Yourself?
We handle all of this on every weekly visit — documented, consistent, and backed by a 50% off first month offer. No contracts.
Get a Free Quote →Pump Lid O-Ring (Most Common)
The rubber o-ring that seals the clear pump strainer lid is the most frequent culprit. It flattens, cracks, or loses elasticity over time. Even a hairline gap is enough to pull air into the system continuously. This is a $5 to $15 part available at any pool supply store. Replace it, lubricate the new one lightly with o-ring grease (not petroleum-based), and make sure it's seated correctly in the groove. This fixes the problem more often than anything else on this list.
Union Fittings on the Suction Side
The unions that connect the pump to the plumbing can work loose over time, especially after anyone has serviced the equipment and not hand-tightened them fully. Check that both unions on the inlet side of the pump are snug. Don't overtighten with a wrench — these are plastic and hand-tight plus a quarter turn is usually correct.
Low Water Level
If the water level drops below the skimmer opening, the skimmer pulls air instead of water. This happens faster than most people expect in a hot Inland Empire summer. Check the water level first before anything else — this costs nothing to diagnose and fix.
Cracked Skimmer Body
The plastic skimmer body can crack at the faceplate, the throat, or at the fitting where it connects to the suction line. A hairline crack can pull significant air while being nearly invisible. Running your hand around the skimmer body while the pump is off and looking for any visible separation or discoloration near the crack is a start. Professional leak detection with pressure testing is the definitive answer.
Cracked or Loose Pipe Fittings
UV exposure and heat cycles cause PVC fittings and pipe sections above ground to become brittle and crack over time. Check any accessible fittings between the skimmer and the pump for cracks, gaps at glued joints, or fittings that have backed out slightly.
The Shaving Cream Test
With the pump running, apply shaving cream to each fitting, union, and accessible joint on the suction side one at a time. Where the cream gets sucked in toward the fitting, that's your air entry point. This works well for above-ground plumbing and accessible fittings. Underground leaks require pressure testing.
💡 If you've checked the o-ring, unions, and water level and still have air in the system, the leak is likely underground. A pressure test on the suction line will confirm and locate it. This is not a DIY fix — but it's a fast one for a professional with the right equipment.
We handle leak detection and equipment repairs across Riverside, Corona, Norco, Eastvale, and Jurupa Valley. See our full equipment repair page for what we cover.