Why are there air bubbles coming out of my pool jets?
Air bubbles at the return jets mean your pump is pulling air into the system, not water leaking out of it. Everything between the pool and the pump impeller is the suction side, and while the pump runs it is under vacuum, so a gap there sucks air in rather than dripping water out. That air gets churned into the water at the impeller, passes through the filter, and comes out the returns as a stream of bubbles. This is why a leak you can never see as a puddle still shows up plainly as bubbles across the pool.
The single most common cause is simply a low water level. When the water drops to or below the mouth of the skimmer, the skimmer starts gulping air along with water, and that is the air you see at the jets. A pool loses water to evaporation, splash-out, and backwashing faster than most owners expect, so before chasing anything mechanical, check that the water sits at least halfway up the skimmer opening and top it off if it does not.
If the level is fine, the next suspects are all seals and fittings on that suction side: the pump lid and its o-ring, the drain plugs on the pump, the unions where the plumbing threads into the pump, and the o-rings inside any suction-side valves. A pressure-side problem (anything after the pump, including the filter and return lines) leaks water instead, because that side is pushing under pressure. So a stream of bubbles at the returns almost always sends you to the suction side to look. If the pump is also struggling to catch prime, the companion read is how to prime a pool pump.
How do I know it is a suction-side air leak?
The fastest confirmation is to look inside the pump while it runs, through the clear strainer-basket lid most pumps have. If you see the water level in the basket sitting low, swirling, or churning with air instead of sitting full and calm, air is being drawn in ahead of the pump, which is the definition of a suction-side leak. A healthy pump basket runs full to the top with clear, still water. Air trapped and spinning in there is your proof, and it also tells you the leak is upstream of that point.
It helps to understand why it is almost never the pressure side. The suction side runs under vacuum and pulls air in; the pressure side runs under positive pressure and pushes water out, so a gap after the pump makes a wet spot or a spray, not bubbles at the jets. That single rule cuts your search area in half: from the skimmer and main drain, through the suction pipes and valves, to the pump lid and the pump inlet, and no further.
Watch the timing, too. Bubbles that appear the moment you turn the pump on and clear within a minute or two are just trapped air purging out, which is normal after you clean the skimmer or pump basket. A leak makes bubbles that never stop, or that get worse as the pump runs and the basket empties. Persistent bubbles plus a low, swirling basket is the combination that means you have a real air leak to find, not a startup burp.
Where is the air getting into the system?
Work the suction side from cheapest and most likely to hardest, and you will usually find it fast. Start with the water level and the skimmer, then the pump lid and its o-ring, then the pump drain plugs, then the unions and valve o-rings. After a low water level, the pump lid is the top offender: the o-ring under it dries out, flattens, or picks up grit, and stops sealing. Pull the lid, wipe the o-ring and its seat clean, coat it with a Teflon-based pool lube (never petroleum jelly, which swells the rubber), and reseat the lid hand-tight.
The skimmer itself is worth a look next. A clogged skimmer basket or a stuck weir flap can starve the pump for water and let it draw air, especially as the level drops during the day. Clear the basket and make sure the weir door swings freely. While you are there, check the small drain plugs on the front of the pump; they each have an o-ring, and a plug that backed out even slightly is an easy air path.
Further up the list are the plumbing connections: the threaded unions that join the pipe to the pump, the o-rings inside any multiport or diverter valves on the suction line, and the pump inlet fitting itself. Threaded fittings on the suction side need a proper thread sealant or fresh Teflon tape, because a joint that only weeps a little water under pressure will pull a lot of air under vacuum. A hairline crack in the pump housing, basket, or a fitting does the same thing. If cleaning the pump and filter is overdue, a restricted basket makes air problems worse, so see how to clean a pool filter.
How do I find and fix the leak?
With the pump running and the basket showing air, go joint by joint on the suction side with a simple water test. Pour water from a hose or cup over each suction-side connection in turn; when the bubbles briefly slow or stop, the water is being pulled into that gap instead of air, and you have found the leak. Some owners smear a little shaving cream or a thin bead of pool putty over a suspect joint and watch for it to get sucked in. Work slowly from the pump backward toward the skimmer so you do not skip the easy wins.
Once you find it, the fix matches the part. Reseat or replace a flattened o-ring, hand-tighten a loose union or pump lid, snug a backed-out drain plug, or reseal a threaded fitting with fresh sealant. Do not overtighten plastic unions and lids; hand-tight plus a small nudge is enough, and cranking on them cracks the plastic and makes a new leak. Replace any o-ring that is cracked, flat, or stretched rather than trying to reuse it, since a two-dollar o-ring is the whole fix in most cases.
A few leaks are harder. An underground suction line, a cracked skimmer throat, or a leak on the pump inlet you cannot reach by hand can call for a pressure test or a pro. If the pump also hums, leaks water, or will not hold prime, the broader diagnosis is in pool pump repair. And if the pump keeps losing its water and airbinding after you fix the obvious gaps, walk through how to prime a pool pump to clear the airlock and get a solid catch.
Is it bad to run the pump with air bubbles?
Yes, running a pump with an air leak is hard on the equipment and should not be ignored. A pump that is pulling air is not fully primed, and a pump that runs low on water runs hot, which cooks the mechanical seal and can eventually seize the motor. The seal that keeps water out of the motor bearings depends on water flowing through the pump to stay cool and lubricated, and air starves it. Left alone, a small air leak that costs an o-ring today can cost a pump seal or a motor later.
Air also chews at the impeller through cavitation. When air and low pressure form and collapse tiny vapor pockets against the impeller, it pits the plastic and slowly wrecks the pump's ability to move water, on top of the noise and vibration you can hear. Your filtration suffers the whole time, because a pump moving a froth of air and water is not turning the pool over properly, and the water can go cloudy even with the chemistry in range.
There is a safety angle on the filter side, too. Air collects at the top of the filter tank, and on a pressurized sand or DE filter that trapped air must be bled off at the air-relief valve before you ever open the filter. Never open a filter or loosen the clamp band with the system pressurized and air trapped inside, because the lid can blow off with real force. Fixing the suction leak stops the air from collecting there in the first place, which is the safe and correct answer rather than bleeding the filter every day.
When are pool bubbles actually normal?
Not every bubble is a problem, and it helps to know the harmless ones so you do not chase a leak that is not there. Bubbles that appear right when the pump starts, or just after you clean the skimmer or pump basket, are trapped air purging out and should clear within a minute or two. Opening the pump lid always lets some air in; watching it flush out on startup is expected. Only bubbles that persist or worsen point to a leak.
Saltwater pools have their own normal bubbles. A salt chlorine generator makes chlorine by splitting salt water, and that process releases a fine stream of hydrogen gas as tiny bubbles at the return nearest the cell, which is completely normal and not an air leak. The tell is that they are very fine, come only from the return closest to the cell, and stop when the cell cycles off. There is more on running a salt system in saltwater pool maintenance.
Finally, a spa or a pool with a spa spillover often has a venturi or air line that injects air on purpose to make the water bubble and churn. If the bubbling comes from spa jets or a dedicated air control, that is the feature working as designed, not a fault. Rule those known sources out first; if the bubbles are a steady stream from the ordinary pool returns, with a low and swirling pump basket, then you are back to finding a suction-side air leak.
Frequently asked questions
Is it bad to run a pool pump with air bubbles?
Yes. A pump pulling air is not fully primed, so it runs hotter and drier than it should, which cooks the mechanical seal and can eventually seize the motor. The air also causes cavitation that pits the impeller, and your filtration suffers the whole time because the pump is moving a froth of air and water instead of a solid column. A small air leak that costs a two-dollar o-ring today can cost a pump seal or a motor if you keep running it. Fix the leak rather than living with the bubbles.
Will the air bubbles go away on their own?
Only if they are startup bubbles. Air that purges out within a minute or two of turning the pump on, or just after you clean the skimmer or pump basket, is trapped air clearing itself and is normal. A steady stream that never stops, or that gets worse as the pump runs and the basket empties, is a suction-side air leak and will not fix itself. If topping the water off to mid-skimmer and reseating the pump lid o-ring does not clear it, you have a leak to find and repair.
How do I get air bubbles out of my pool pump?
First rule out and fix the source: top the water up to at least halfway up the skimmer, clean the pump and skimmer baskets, and reseat or lubricate the pump lid o-ring. Then reprime the pump by filling the strainer basket with water, seating the lid, and restarting so it catches a full basket of water. If it will not hold prime, work through the suction-side joints with the water-over-the-joint test to find where air is getting in. Persistent air after all that usually means an o-ring, union, or fitting that needs replacing.
Can too much chlorine cause bubbles in a pool?
No. A chlorine overdose does not produce a stream of air bubbles from the return jets; that is an air leak on the suction side, not a chemistry problem. The one real chemical source of bubbles is a saltwater pool, where the salt cell releases fine hydrogen bubbles as a normal byproduct of making chlorine, and only from the return nearest the cell. If the bubbles are coarse, come from every return, and pair with a low, swirling pump basket, look for an air leak rather than blaming the water balance.
Why am I getting air in my pool filter?
Air collecting at the top of the filter tank comes from the same suction-side leak that blows bubbles out the returns; the air is pulled in ahead of the pump and rises to the top of the filter. Bleeding it off at the filter's air-relief valve is only a temporary fix, and you should always release that pressure before opening the filter so the lid cannot blow off. The lasting fix is to find the suction-side gap, usually a low water level, a dried pump lid o-ring, or a loose union, and seal it so no air enters the system in the first place.