Why Are There Bubbles in Your Pool?

why are there bubbles in your pool

Many pool owners experience a shared problem that arises at the beginning of every pool season — air bubbles coming out of their pool’s return jets. In conjunction with that issue, another concern that develops is pump priming malfunctions. Thankfully, there is just one cause for both of these dilemmas: air in the pool pump.

Your pool pump has two main sides, the suction side and the pressure side. As the name suggests, the suction side sucks the pool water through the pipes, then sends it into the pump impeller. Once the water gets past the impeller, it flows to the pressure side, where it’s then sent back out into your pool. Because the suction side draws water in, rather than pushing it out, if there is air in your pool pump, it’s coming from the suction side.

How is the Air Getting in the Pump?

To find out why air is in the pump, inspect the pool skimmer, the pipes and valves, and finally the pump itself. There are multiple parts that make up the suction side, so it may take a bit of time to thoroughly examine each part. Thankfully, resolving suction side issues is relatively simple. Let’s begin!

1. Low Water Level

The water level of your pool should always be at least halfway up the opening of the skimmer. If the level drops too low, the skimmer will suck in air along with the water. Resolve this by simply adding more water to your pool.

2. Skimmer Basket

Skimmer weirs can stick if the skimmer walls bow inward. If the weir gets stuck in the up position, blocking water flow, remove it and trim a bit off on each side. You can also replace it with a more narrow spring loaded weir. Avoid toys or rafts becoming stuck in the skimmer, by clearing the pool of all gear after swimming.

3. Pipes and Valves

Cracked pipes in the suction side of your pump can cause a high influx of air in the pump. Check for any damaged pipes by pouring water over the pipes while the pump is turned off. If bubbles appear on the pipes, that indicates a crack and the pipe will need to be replaced.

Valves turned in the wrong direction will restrict water flow to the incoming lines and force the pump to go into overdrive. This results in higher vacuum pressure and draws in air around the incoming valves. Make sure all valves are open, and not closing off any lines.

4. Strainer Basket Plug

The plug on the strainer basket acts as an air-seal, so any damage will allow air in the pump and cause bubbles in your pool. Simply inspect the strainer basket plug and replace the o-ring if it is damaged or worn.

5. Loose Pump Lid

The pump lid also acts as an air-seal for the pump system. Check the pump for any worn o-rings or cracks in the lid. Patching a crack is a solution, but only a temporary one. The crack will always come back, so it is best to replace the entire lid.

6. Loose Drain Plugs

Loose drain plugs can result in air in the pump. If your pump drain plug uses an O-ring, and many do nowadays, make sure it’s still intact; they only seem to last 3-5 years before dry-rotting. If your pump drain plug does not use an O-ring, use Teflon tape on the threads and tighten with pliers. For best results, remove previous layers of Teflon tape, and wrap it three times (in a clockwise direction as the threads face you), with new Teflon tape each spring, or whenever the pump drain plugs are removed.

7. Filter Was Recently Cleaned

When the filter tank is opened and cleaned, it can take a while before all the air is pushed through the filter and sent to the pool returns. Avoid this by always opening the air bleeder on top of the filter tank when restarting the pump. Let the air bleed out until a steady stream of water is spraying. It’s normal for a few handfuls of air to remain in the filter tank, so don’t be surprised if there seems to always be just a little more air in the tank.


Air bubbles in your pool can leave pool owners scratching their heads, wondering what the cause is. Thankfully, the cause is usually localized to one area, the pool pump. Diagnosing why your pool pump is sucking in air can be time consuming, but with a little detective work, you’ll find the problem in no time. While a damaged pool pump might seem catastrophic, it is usually a quick and easy fix. Follow these steps to diagnose and repair your pump, and say goodbye to bubbles!

45 thoughts on “Why Are There Bubbles in Your Pool?

  1. Daffodil McCurdy

    Hello. My pool pump was turned on accidentally (automatic Mode) while the pool was empty and drained (it had plaster repair). It may have run for an hour or so. Is it safe to turn the pump on now that the pool is filled with water? Or is there something else I need to do first. Thanks

    • Yes, safe to turn on. Chances are, no problems. If there are problems, it may be a leaking shaft seal, or a shrunken (and leaking) plumbing fittings, in or out of the pump, or in worst case, a warped impeller, basket or housing.

  2. Brandon Fullingim

    Our actual pool seems to have more pressure than normal, and the filter cartridge seems to be lower pressure than normal? We can not keep our pool clear! Our local pool company says everything is fine, pool sample is good, but my pool is still green? I think I have a filtering issue, pressure issue or something ? My pool Polaris will even run really slow when the Polaris isnt on?

    Can anyone help or know what they think the issue is ?

    • Brandon, have you replaced the filter cartridge? It may have small holes that are allowing water to pass thru, or the filter may be missing internal parts like a manifold, allowing water to bypass the cartridge, or the cartridge is not seated fully, also allowing bypass… hence the lower filter pressure, but higher flow at the wall returns.

  3. Donato D'Angio

    We mistakenly removed the pool vacuum from the water before removing the hose in the return. A small amount of air got in. Everything is air tight. What’s the best way to remove this air? Thanks

    • It will push thru naturally, or you can open up the air bleeder, found on top of most pool filters.

  4. Ahmed Saadallah

    am seeing now air bubbles in my pool just after I cleaned my DE filter.

    I re opened again and glue the o ring and tightened the belly band and still not seeing the bubbles

    What to do NOW please

    • Release the air from the air relief valve on top of the filter. If air continues, it is coming from IN-FRONT-OF the impeller, in the pump. Look for air leaks in the pump lid, the pipe that goes into the pump, or the suction side valves

  5. Jimmy L Wallace

    So I am filling an above ground pool for the 1st time and there are air bubbles on the bottom everywhere. As they were rising I was thinking oh Lord. Is this normal.

    • Are you filling it with Perrier? 🙂 I guess that sounds normal, this article is about air coming from the filter system, being sucked in by the pump and pushed out into the pool. If you are talking about air bubbles on the bottom of the pool, while filling… well, not sure what causes that, but I don’t think it’s cause for worry!

  6. Craig O'Brien

    I read all of the above issues and mine doesn’t seem to have come up. I moved into a new house in late August. My pump worked fine until last weekend. Now I’m getting air in the basket and there’s a strange oscillating sound coming from the pump.
    When the pump is on my basket is about 2/3 full. I can hear air in the system (ie – through the pump and filter, and in the separate chlorine piece). When the pump is off there’s barely any air in the basket. It seems fun (but for a tiny bit of air).
    Reading the (great) article above, I should be looking for leaks on the ingress side – I can’t find any above ground.
    Given that the basket is full of water when the pump is off I’m concerned that there’s something wrong with the pump. In fact…. I think this might have started after I (stupidly) backwashed the system without having a basket at the pool end. I’m worried that I pulled leaves into the system and they’re disrupting the pump’s spin.
    Is that a known issue? My pump is an oldish 1 phase Hayward.

    • Hi Craig, you may have hit the nail on the head – the pump impeller may be clogged with small debris. If you remove the pump basket and reach your fingers thru the volute, into the eye of the impeller, you may feel debris stuck in there. If so, pull the pump apart and clean – I have another blog out there somewhere with more detail on cleaning a clogged impeller. If that’s not it, spray shaving cream around the pipe fitting that threads into the front of the pump, to see if it gets sucked in, while the pump is running. Or wrap duct tape tightly, to see if pump flow improves. The most common air leak is on the pipe fitting. If you have pump unions on the ingress side, check that the union nut is tight, and the o-ring is in place, and not damaged. If that doesn’t help, feel free to send me some pics and more thoughts to swimmers -@- intheswim.com. – Davy

  7. I have an old pool (30 yrs). 1 skimmer, sand filter, 2 return jets.

    My pump basket has air and never fills right up and has air cavacting. I also have some air bubbles coming from 1 jet. I’ve tried everything I can think of (short of going underground) to find an air leak… No luck.

    I’ve ignored it for a long time, but recently the heater has strated shutting off (low flow).

    I called a pool company and the tech couldn’t find a suction side leak either. What he did (admittedly as a hack fix) was install small return jets to create back pressure. How my sand filter is running at around 19psi (instead of 10).

    My pump basket still is only about 90% full, but its now quiet and not cavicating. The odd part, is that I have zero air bubbles coming out of the jets now. Actually, I do get air bubbles when the pump starts up in the morning. But after 5 minutes or so, the air is gone.

    Is this jet restriction a bad idea? Any idea what the heck is going on?

    • Hi Chris, the air leak could be from anywhere on the suction side, but usually around the pump lid or drain plugs, or the pipe threading into the pump, or the skimmer or main drain valves. Sounds like the pump is a bit large for the system. It’s a good idea what your (smart) pool guy did, to balance out the suction and pressure sides of the pump. The restriction reduced the suction-side vacuum, which reduced the air intake.

  8. David Templeman

    I have no bubbles come into my pool,however,every time I shut down the pump the water in the bleed valves disappears, and requires bleeding when stared up again.
    I have looked at the rubber ring around D the debri basket its can and looks good,I cannot see any leakers or hear any air comeing out from the pump, or the large filtration thing which has the sand in it.
    It all works fine but I have to be there to start it up with a flow of water to get the pump going,M once going it works fine until I shut down and then the water drops instantly in the bleeder. Help please, regards
    David

    • Hi, a bit of drain down is normal when the pump shuts off. If however the pump loses prime, and needs to be refilled with water before the pump will actually pump water – that’s a larger problem. It usually is related to an air leak, on the filter or pump, which allows the water to drain out of the filter and pump and go back into the pool. Such air leaks are often ‘water leaks’ when the pump is on, but when the pump shuts off, begin to pull air in, as gravity allows the water to flow back to the pool. Installing a check valve in front of the pump is a way to fix the situation, if you cannot find and fix an air leak…

  9. This article is very helpful – Thank you! I have a spa with an overflow edge that flows into a trough and has an auto-fill feature. The spa works fine until people actually use it. What happens is, when people get out the trough water gets lowered for some reason and the pump begins to suck air. Would trapped air cause the spa to lose water?

    • Hi Kevin, I suppose what is happening is when people get IN to the spa, the water level rises and flows out of the spillway, then when they get OUT of the spa, the water level is below the spillway, which causes the trough to empty, as it is not being constantly refilled by the spillway. But if it’s all the same water, in the spa and in the trough, you would think it would refill in time – I guess I’m not sure, without being there, it’s hard to say…

  10. Having difficulty finding an air leak. Is it possible that a replacement pump too small for the pool can cause bubbles under the premise that the flow is simply low to pull out all the air?

    • Hi Frank, it’s just the opposite actually, a lower flow pump won’t have the power to pull air into the system. I guess you have read the post, so already know my tricks, like looking for the spray back after shutting off the pump, or using shaving cream around the pipe coming into the pump, or using a Drain King to pressurize the suction side? In most cases it is the threaded pipe coming into the pump, but can also be a drain plug on the pump – but it will always be before the impeller, not after. It could be a loose valve (skimmer or main drain), and sometimes it is a vortex in the skimmer, drawing in air, and sometimes it can be a cracked skimmer pipe underground, but not usually…

  11. Air leak in the skimmer return line. I’ve checked for leaks, but have found nothing, but during heavy rain fall, when pool fills to max ( above skimmer box) , bubbles go away?
    Any suggestions?

    • Hi Kevin, then it could be the skimmer drawing in air perhaps? Some skimmers will create a suction vortex and draw air in when the water level is low. I suppose that heavy rain fall may also seal up any air leaks temporarily, if there is enough water to keep air from sucking in…?

      • Similar situation. Changed all fittings, o-rings, valves on suction side to try to solve minor air suction problem. Air bubbles still visible in strainer basket and returning outlets after changing. Usually keep the water level of the pool half way up skimmer. No visible water vortex around the skimmer or an inlet that is located lower than the skimmer when the water level is at the mid skimmer level. Recent heavy rains raised the water level to the top of the skimmer. No air bubbles now. ???

        • Hmmm, not sure why that would be, if not a vortex in the skimmer. Might just be a coincidence? Or, possibly a crack in the plumbing line. If you feel up for it, grab a shovel and dig down along the skimmer pipe(s), dig straight down to expose the 90 fitting, then keep digging around the pipe to expose the pipe as much as possible for full inspection, looking for ‘spider web’ cracking, or listen for an air leak, which will be a water leak when the pump shuts off. Or you may find nothing, but peace of mind! 🙂

  12. Question, I have three suction lines. One with a valve for the spa suction line, and the two others, one for the Pool Main drain and one for the Pool Skimmer, that merge with a three way valve.

    If I close the Spa and Skimmer suction lines, leaving the main drain line only open, I see my sand filter start filling up with air. I also see many air bubbles in the pull gasket lid.

    But if I close the main drain suction line and only open either the Skimmer or the Spa suction line, I don’t see this issue.

    I called a pool maintenance guy to take a look at it. He said he doesn’t think there is any air leak in to the pool system, but that the air bubbles I get( from when I only run with the main drain line only) are due to the pump generating gas bubbles from the pool pump pressure water starvation.

    Could he be right? I just can’t find any blog saying this could be one case for air bubbles in the pool basket lid. Everything I find only is an air leak.

    Not sure if what he was talking about is the water liquid, solid, gas phase stages, where water is turning in to gas due to the pressure on the suction side of the pump when I starve it by only opening the main drain line?

    Or is he wrong and there is no way gas can generating in the gasket and must be only an air leak?

    More info:
    Pool is 18 years old.
    Recently a hole was dug on the group relative close to the pool lines, but contractor dug around the hole to assure me he didn’t puncture any line.

    Thanks for your help and recommendations.

    • Hi Joe, he could be right, I think I have seen evidence of that in the past, but I probably just guessed that because the pump adn pipes are under such great vacuum pressure (with only one line open and cavitation setting in), that the pump finds places to leak air, places that normally would not leak air, like around the pump lid o-ring, or valve lid o-rings, or valve diverter stems… To check – here’s two ways, one is to spread paper bags or newsprint below the pump and pipes, and with the pump running full head on mMD only, shut off pump and look for any instantaneous spray or spritz of water at the moment the pump shuts off – that would be the air leak. If that fails another way is to spray a thin bead of regular shaving cream around all joints – pump lid, pipe coming into pump, drain plugs, valve lids, diverter stem, pipe joints, etc. and leave the pump running on MD only to see if the shaving cream divots, and starts to get sucked in, at any spot. Third – is to just not worry about it, your filter is not really filling up with air, just a bit in the top, so it has no real effect on filtration, and how often do you run MD only anyway? 🙂

  13. greathel fasvresu

    when my cleaning jets pop up I see air bubbles. what do I need to do,?

    • Hi Greathel, there is an air leak, on the suction side of the pump, or before the impeller. Common areas include the pump lid (must be very tight, with lubed lid o-ring), and the threaded pipe that comes into the front of the pump (must be very tight and sealed – if loose, use Pool Putty to fix, or replace the fitting). Air can also enter the system from low water level or a stuck skimmer weir, bringing air in from the skimmer, or from loose and leaky suction side (skimmer/main drain) valves. Seal up the air leak in the front of the pump, then bleed off all the air in the filter tank, and the bubbling should cease.

  14. Jennifer Denecour

    I am ready to fill this pool in, as I am so frustrated. I had someone open the pool but essentially all I think he did was remove the cover and shock it. The pool since, has turned a milky blueish green. I have had the water tested, dumped a bunch of chemicals in, before finally changing the sand in the sand filter yesterday. I put some shock in and ran the filter all night hoping to see a change by today. Still nothing. the pool guy I had said everything seems fine filterwise and it must be a chemical issue(he has since sorta quit on me because he lives too far away!).I just tested the water and my TA is at 120, my pH is at about 7.2(low I guess). I did see lots of bubbles coming out of the shallow end jet and found a leak on the pump and tightened it. It is still bubbling though and I wonder if there is another leak somewhere or just the air coming out from the previous. Do you have suggestions on what to add to the pool? I have 7 tablets of chlorine in the chlorine pump. I am at a loss. Any help is much appreciated!

    • Hi Jennifer, the remaining air may be trapped in the filter, open the filter air bleeder to let it escape. If it starts again, you likely have another air leak (or the same one), usually on the pump lid, drain plugs or the pipe going into the pump, but can also be leaky suction side valves (skimmer/main drain).

      Sand filters are the worst performers for cloudy water, or poor conditions clean-up. They pass thru particles that other filters would trap. Two things you can do is to add a cup of DIcalite perlite filter powder thru the skimmer, to act as a filter aid, or use the Slime Bag, which attaches to the return line, as a secondary filter, trapping particles to less than 5 microns. Using a Clarifier can also help of course, and running the filter 24/7, backwashing only when pressure rises 8 psi or higher. Sand filters are great for everyday filtration, but they choke a bit when conditions are bad…even with new sand.

  15. I have a similar issue. I have air coming out only one of my return jets in the pool- the one farthest away from my pump and filter.

    My return line comes out of my filter and then splits in to two lines about four feet away. Both lines then travel across the width of the pool (16 feet) with one line going into the deep end (this line does not have air bubbles) and then the second line travels the length of the pool (10-12 feet) to the swallow end- this is where I have constant air bubbles.

    Thoughts? Thanks in advance…

    J

    • Hi Jay, the air coming out of the farther return is unusual, but it can happen, as it is easier for the air to travel in a straight line, than take a turn at the Tee fitting… The source of the air is still, and always, before the pump impeller – either the pump lid, drain plug or pump seal, but usually the threaded pipe that is screwed into the inlet port of the pump, or possibly a leaky skimmer or main drain valve.

  16. I am having a strange issue. I can run my main pool pump without an issue, jets are fine, no air bubbles in the strainer basket. But when I turn on my booster pump for my cleaner, it runs for about 20 minutes and the jets stop pumping and the cleaner just stops. When this happens, I notice air bubbles in the strainer basket….any ideas as to what is causing this? Also, there are no visible leaks to be seen.
    Thanks

    • Hi Roy, you have my attention, this is interesting. In most typical installations, the booster pump draws water from a tee fitting that is on the pool return line. When the system is tight (no air leaks) all runs fine. What I think may be happening, is that there is an air leak on the suction side of the filter pump, (before the impeller), and the suction of the booster pump is pulling water strong enough to pull air into the filter pump, when it won’t happen while the booster pump is off. The usual place for an air leak is on the threaded pipe fitting that goes into the filter pump, secondary sources will be the pump lid o-ring, pump drain plugs or a leaky skimmer or main drain valve, or leaky pump union (in Front of the pump, not after). Look for the air leak and seal it up, you should be back in business. Davy

  17. Starting up my pool and I must have a air leak. I switch the hoses etc. Filled the pump skimmer full. Turn on pump and it works for abut 3-4 seconds then looses water in the pump skimmer. The basket doesn’t seem to catch up. It does for a few seconds once in awhile but loose suction again. I left it overnight to see if there is a leak anywhere and it was dry. Suggestions?

    • Davy Merino

      Hi Rob, ah pool opening, always fun! 🙂 Here’s some things to check – MOST COMMON PUMP AIR LEAK PROBLEMS
      1. loose pump lid (they must be TIGHT), missing or damaged or dry pump lid o-ring – use teflon pool lube.
      2. loose hose adapter, threaded fitting coming into pump must be tight! Use Teflon tape or other thread sealant.
      3. loose valve lids in front of the pump, skimmer and main drain valves that are old and leaky (inground pools).
      4. low water level in the pool, or a stuck skimmer weir or pool toy, blocking water flow into the pool skimmer.
      5. loose hoses, not clamped tightly to hose adapter, or tiny splits in the suction hose (usually can be heard hissing).

      Good luck!

  18. Bruce Reisman

    I am unable to find the air leak. Can the pump suck air through the impeller shaft seal?

    • Davy Merino

      Normally not, but i have seen it happen on one occasion. In most cases, a bad shaft seal will only leak water, and not draw air in, because it is under pressure, not under suction. But it could happen! If you have a clear pump lid and can see an air tight basket area, but the filter still fills up with water – it could be the seal, but it would also be leaking water when the pump is off, if it is leaking air when the pump is on. A good trick to isolate air leaks is to use a Drain King, connected to the skimmer, used to pressurize the suction side of the pool plumbing (up to the impeller). When under pressure, an air leak in front of the impeller will become a water leak.

  19. What if the bubbles comes out only when you turn the valve partially to suck air from the main drain and from the skimmer but it does not happen when you close the skimmer valve

    • Ah good question, if you close one line completely and the air stops, you may deduce that air is coming from that line, or that valve. Jandy type valves can draw air in around the handle stem, two small orings are used, under the cover, and it also has a larger cover oring that can fail. Sometimes just the lid is loose, or tightening the knob will stop the air. If you have union valves (Hayward), there is an oring around the valve body, and internal seals on some models, and also handle stem orings. You can pressurize a line using a drain king on a garden hose, to see where a leak occurs, or use shaving cream to see where it sucks in. The most common air leak on systems is not the valves, but the threaded fitting that screws into the pump, second most common is loose pump lid, or unlubed or damaged pump lid oring. But when it leaks air only on a certain valve setting, you may be onto something – but usually, closing one incoming line makes the pump suck harder, or work harder and cavitate, which leads to more air being pulled in, thru the tiny voids.

  20. Why would I only have air bubbles coming out of one return jet and not all three?

    • Hi Tonya, the air will just come out of the return closest to the pump usually, it’s too lazy to travel all the way to the others, which are all part of the same pipe.

  21. […] the water level during winterization. Pool leaks can rapidly cause a loss of pump prime, as can air leaks in front of the pump (unrelated to water level). Any situation that causes your pump to lose prime, […]

  22. Mark Andrews

    Hey, regarding Tip #5… can the drain plug actually draw in air and NOT be leaking water at the same time. I have no signs of water drips; wouldn’t that be the tell-tale sign? Thanks.

    • Yes – the drain plug can draw air in, and not be leaking, at the same time. If the drain plug drips water when the pump is off, it is sucking in air when the pump is on. But if your drain plugs are not dripping when the pump is off, your air leak is likely not there.

      Most pump air leaks occur on the threaded fitting that screws into the pump. The threads can shrink with high heat, allowing air to be drawn in. Pool Putty can be used as a temporary, but long lasting repair, but the correct repair is to cut-out and replace the PVC fitting, (usually a male threaded adapter, 1.5″ or 2″), using thread sealant when installing.

      For pump drain plugs, apply Teflon tape around the threads, first removing any old tapes or sealant. Many drain plugs also use a small o-ring, which can be necessary to replace every 5-10 years.

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