How to Identify and Correct Air Leaks

Written by:  Danny Rhodehamel

If you are seeing a significant number of bubbles coming out of your return lines into the pool, you probably have an air leak in your filtration system. Possible sources of this problem are low pool water levels, leaks around the strainer lid, leaks in the unions or leaks in the pump seals. For optimum pool pump operation, the source of the leak must be identified and corrected.

Tips & Warnings


Step by Step

Step 1
swimming pool filtration system

Your swimming pool filtration system has two sections: the suction side (from the pool to the pump) and the discharge side (from the pump to the pool). Check the strainer pot of your pump. If you see a significant number of air bubbles moving through the strainer pot, you know that the air leak is somewhere on the suction side of the system plumbing before or at the pump.

Step 2
pool water level

Go over to the pool and check the water level. Ideally the pool water level should be at least halfway up the skimmer intake. If the water level is below this level, the skimmer is probably sucking air into the skimmer pipe to the pump. This is a simple problem to resolve. Simply fill the pool to the halfway point of the skimmer. Also check that nothing is holding up the flap of the skimmer opening to the pool. This could also let air into the skimmer suction pipe.

Step 3

If the pool water level is adequate, your next step is to check the strainer lid on the pump. If it is not on tightly, you may be sucking in air around the lid. To check the lid, first TURN OFF THE POWER TO THE PUMP at the breaker box.

Step 4
pool pump strainer lid

Remove the pool pump strainer lid. These are generally screwed on or are secured with toggle bolts. Pull the O-ring out of its groove. Clean out any debris that might be in the groove. Check the O-ring for any cracks or wear. Sometimes an older O-ring is stretched so that it bulges when you try to replace it in its groove. This is a common source of leaks. When you screw on the lid, the O-ring will bulge out and create a leak. Replace a worn or stretched O-ring. Also, it's a good practice to lubricate the O-ring lightly before replacing the lid. Use a good pool seal lubricant (Teflon or silicon). DO NOT use petroleum jelly.

Step 5
pool pump stainer lid

If your pool pump strainer lid was not the problem, check the union commonly inserted before the pump. Again make sure that the power to the pool pump is turned off before unscrewing the union.

Step 6

After separating the union, you should see an O-ring in the groove of the union. As mentioned in Step 4, check that this O-ring is not worn or cracked and that it is seated correctly in a clean groove. Lubricate the O-ring. Retape the threads of the union with two or three layers of Teflon tape and reconnect the union. Tighten the union by hand.

Step 7
pool pump motor shaft seal

If these steps have not corrected your air bubbles, and you have an older pool pump, you may have a leak in the motor shaft seal. The picture (left) shows the location of the motor shaft seal in a cutaway version of a Hayward pump. For instructions on replacing a motor shaft seal go to our guide, How To Replace A Motor Shaft Seal.

Step 8

Another source of air leaks is the motor's drain plug on the suction side of the motor. If this plug is loose, tighten it to stop the leak.

Step 9

If you still have a significant number of air bubbles coming out of your return lines into your swimming pool, you may have a bigger problem like leaks in your underground lines. Call a pool maintenance professional to help you isolate your problem.

Comments (41 to 80 of 241)

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User: Inyopools

start up bubbles - It's normal to have some bubbles show up in your pool's return lines when you first start up. The system is just purging any air that gets in the lines when the pump is off.


I opened my pool no problems but now four weeks later ONLY when I start the pool pump I get air bubbles (only for a few seconds)from both each return line and then the bubbles go away. No other time do I have bubbles. What could this be?

User: Inyopools

krusekm - Sounds like your filter is blocked. If you just opened your pool and used your filter to clear the debris, you may have to backwash/rinse your filter 3 or 4 times to clear the debris. If you haven't changed your sand in 5-7 years, that may be the problem. Also, many filters have breather tubes from the bottom to the top of the filter tank to relieve any air trapped at the top of the filter. Make sure that tube is clear.

User: krusekm

Hello. We are having issues with the following of our inground pool with a sand filter system: Bubbles appearing in pool from return lines, Extreme back pressure when turning pump off blowing water out skimmer line, water sounds like it is trickling into filter from pump, bubbles in strainer before pump, need to prime pump every time to get started, pool not cleaning up as it used to before the bubbles started. If system in recirculation mode, pressure seems good and if turned off it does not blow back. Not sure what the problem is. Thank you for your time.

User: Inyopools

Ding - You may have an suction air leak in your cleaner hose. Check to make sure the hose connectors are not cracked and leaking. Then remove hose sections one at a time to see if you have a leak in the hose itself.

User: Ding

Every time we try to vacuum the pool we lost pressure on the pump and water at the same time,pls help.

User: Inyopools

hdinh - Sounds like an air leak on the suction side of the pool piping but like you I don't know why it would go up and down. If it is a leak, try isolating it by temporarily packing plumber's putty around each of the suction connections until the pressure is steady. The last one packed in your leak.

User: hdinh

Just opened the pool this past weekend. If I turn the vale to suck from the spa side, pumps and pressure work fine, there is no air bubble in the strainer. But if I turn the valve to the pool side, immediately suction is down, then gets up for a minute, then down again. Does that mean there is an air leak on the pool side? How come the suction keeps going up and down?

User: Inyopools

frustrated - You may have an air leak in a section of your hose that lays on top of the water. Separate the first section of the hose from the rest of the cleaner hose line and with the other end of this section connected to the skimmer, hold that section completely under water so there is no chance of an air leak. If your pump maintains prime, you have a leak somewhere in your cleaner hose. Reconnect the hose together leaving out one section at a time until you find the one that leaks.

User: Inyopools

SMPFL - Whenever something doesn't work after I've made changes to the system, I go back and check the changes to see if I did them correctly. Check that your new strainer O-ring is not defective and seats correctly. Check the steps you went through to clean the filter. Then check to see that your pump's impeller is not partially clogged - a common low pressure problem.

User: frustrated

Hello and thank you for your time. I have a suction problem. I have a 16 x 32 inground pool. When in filter mode all suction is great. I turn offthe main and i suck directly from th skimmer and still all is great. As soon as i hook up my vac automatic or manual, i lose suction. I have a simple 2 line system. Skimmer and main coming up out of ground then into one, then into pump and Filter then out to return. Any ideas why i drop suction after hooking up the vacuum. Thanks again for your time


Hello! Upon completion of replacing the o-ring on my trap basket and cleaning my filter, my pressure gauge is reading 0 pressure (normally run about 10). I replaced the gauge and still have a 0 pressur reading. I then replaced the o-ring on the filter housing, again to no avail. The pump/filter seems to prime as usual and there are no air bubbles in the trap basket and the water is circulating in the pool. What could be causing 0 pressure while it seems all systems are go? Any insight would be greatly appreciated.

User: Inyopools

Dcvetkov – See our guide on “How To Correct Low Water Pressure in Your Pool System” for possible problem areas. One of the most common problems is a clogged Impeller – Step 6.

User: dcvetkov

Hi There

\Trying to open a 10 year old pool, Just replaced the Whole VariFlow Xl Valve., and after few small water leaks, and fittings, now it is fine, but I have very low, pressure, barely 2 PIS, and some bubbles coming from return lines. It seems that suction is fine I cleaned the skimmer and strainer basket, and I do not see obvious source of leak., I may try to replace the O ring in the strainer basket but I think that is not the problem
Back wash line does not work also, just water does not flow through return line or waste pipe for some reason
SAnd is old about 10 years, and I dont think it has been replaced, although I used some products to chemically clean it

I think it is in the Filter is somewhere in the return lines

Water is still very dirty after super shocking the pool, maybe it is not unusual if there is no filtration for 3 days

Any advise appreciated

User: Inyopools

JSG - Glad you found your leak! Sounds like a good way to isolate the leak. However, I would recommend replacing the plumbers putty with silicone sealant as the putty is said to deteriorate the piping.

User: Inyopools

29 yr old skimmer - If your skimmer is working during filtering, it sounds like it is operational. I would question the new cleaner hose and maybe how it is installed. When the cleaner hose is inserted in the bottom of the skimmer, the skimmer should be full of water. If it drains while the hose is in the bottom of the skimmer, air will be sucked into the system. Assuming the skimmer is full of water, try pushing the cleaner hose down below the surface of the water so that everything is below water, the hose and the hose connection into the skimmer. If this works, you probably have a hole in the hose or its connections.

User: JSG

I had lots of bubbles coming out of my return jets also. There was also lots of bubbles visible under the pump strainer cover. After changing the rubber seal under the strainer cover and using liberal lubricant, still lots of air. I finally started applying a bead of plummets putty around each pic fitting on the suction side of the pump. The leak wAs one of the fittings between the jandy valve and the pump. As soon as I covered both those fittings with plumbers putty, the air bubbles were gone. I may apply some good silicone sealant if the plumbers putty doesn't last.


I have brand new pump and vacuum hose..The skimmer which the vacuum goes into is 29 years old..While filtering, there is no air bubbles in return lines..As soon as vacuum is hooked up to old skimmer, air bubbles start to come thru the return lines and shortly after I have no suction to the pool vacuum..It would seem there is a crack somewhere in the old skimmer, that is 29 years old? I am hoping not, since that will be VERY costly and can't afford right now..Any ideas how to determine if it's this built in skimmer? Thaanks

User: Inyopools

Sav - The leak in your return line would not cause air in your pump basket. That air is being sucked in on the suction side of the pump. Recheck all the connections on the piping from the pool to your pump. Sometimes when you shut off the pump, back pressure will cause water to squirt out of a suction side leak and you may be able to detect the leak that way. One other possibility: Your pump may be too large for your system causing an imbalance between the water coming into the pump and water being discharged.

User: Sav

Hello, i have air in the pump basket and tried everything to resolve the problem, but nothing worked. No difference even when i shut off the drain line or the skimmer one (i have two suction lines). I did notice though that i have a small water leak on the return line. Can this be the cause of my problem? My in-ground pool was built 3 years ago and this is the first time i am experiencing this issue.


went to lowes and spent under $4 for some pool lube and did my "0" rings on the suction side of pump. re - primed pump and it started right up with no air leaks. Freakin awesome!!!!??

User: Inyopools

Matt – It doesn’t take much of a hole to cause a suction leak. Replacing the suction hose should correct your suction side leak unless you have other leaks. Holes in the discharge side of the pump do not affect priming of the pump, but if it’s spraying water, you might as well replace it too.

User: Matt

I have a above ground pool with a less than 3 year old hayward 1.5 HP pump. I recently replaced the sand filter as it was cracked and have used this special sand instead of the regular pool sand. (i forgot what the sand is called) The sand filter i replaced was not new, and neither was the sand, but it was still in good condition. Once I hooked it up, I forgot to fill the sand filter with water, and initially the pump blew a ton of this sand back into the pool. So I went to work sucking this sand back up. Put the pump in waste only too see that It filled the entire basket in the pump with sand. This may all be concidential, because once I cleaned it out, it worked fine. Today I discovered some small pin holes on the suction side in the house from the upper skimmer to the pump. It's hard for me to believe that these small pin holes would keep the pump from working correctly. When I turn the pump off the water reverses for a second and air bubbles come out of the skimmer. From what I read I do have a air leak on the suction side, and Im hoping its only this one hose. I also have a leak in the return side. These are easy hoses to replace, I just want to confirm that 3 or 4 little pin hole leaks would cause that much pressure loss. It won't prime, water does continue to come in.

User: Inyopools

FlipJ - It sounds like your system is sucking air through the skimmer. I don't know what the "two holes on the skimmer" refers to, but in order to maintain water flow to your pump, no air can enter the skimmer bottom drain going to the pump. That well has to be continuously full when the pump is on. If you have a leak in or around the skimmer, your pump may be sucking in air through that leak. Turn the pump off and place a few drops of food coloring inside the skimmer. If you have a leak, the food coloring will seep into the leak.

User: FlipJ

We have a 35 year old pool with fairly recent equipment. Today we found the pool suction side pulling air and not filling with water. We have two inputs to the pump, spa and skimmer, and when turned to the spa side there is no problem. Turn to the pool side and starts pulling air and won't prime. We have replaced rings on the Jandy valve, cleaned the skimmer, used a water blast from both the pump and the skimmer and no solution. There are two holes on the skimmer in addition to the pump draw at the bottom, but neither seem to do anything. Any thoughts? Many thanks.

User: Inyopools

Michael - I've been thinking about this for a while and still don't have a good answer. When you went directly to "Waste" you bypassed the filter so your water flow may have been stronger. This may have dislodged a partial clog in the lines coming into the pump on the suction side. Is your pool water flow better now when you put your hand over a return? Not sure how a partial blockage would cause air bubbles unless the pump is sucking harder between the blockage and the pump thus drawing in more air at a small leak? Best I could come up with. Please let me know if someone else has a better answer.

User: Michael

I have a 22 year old in-ground pool and for the past 1 1/2 to 2 years have been plagued by constant air bubbles in the return lines. I had replaced the strainer o-ring several times, replaced the o-ring on the strained plug, replaced the three-way valve at the intake to the strained and the couplings. Nothing that I did had any affect.
I called a national pool service department who came out and looked at it and they recommended I replace the pump but wouldn't guarantee the this would fix the air bubble problem.
Typically when the pool becomes too full because of rain I use that excess water to backwash the sand filter. Done this for years since being in a drought I didn't want to waste water needlessly.
This year we've had some really good rains so rather than backwashing I set the valve to "Waste" and sent the excess directly out to the street.
IMMEDIATELY afterwards the bubbles in the return disappeared. I cannot fathom why this is but it has been a week now with absolutely no bubbles in the return lines. I'm baffled but really relieved!
I have a two speed 1.5-2.0HP pump and use high speed when running the Polaris and when using the vacuum otherwise it is on low speed 24/7.
Any idea of what was happening?

User: Inyopools

Greg - Sounds like you have covered most of the bases. The only other problem I might see is a blown underground pipe in the suction side. If it is significant, you would not be able to prime the pump to even have initial pressure. Please let me know when you find a solution so I can document it for other users.

User: Greg

Marc I have tried several repairs and checks to regain pressue in the suction line..Co2 air blast..bladder blast. replaced diffuser checked impeller ( removed and disassembled motor )replaced gaskets and seals ..removed check valve (stuck shut ) and installed straight line. checked for air leaks using smoke to detect any air going into pipe lines....cleaned DE filters and also replaced housing seal. Replaces psi pressure gauge and all fittings...I dug around skimmer and suction ( barracuda cleaner ) lines and looked for and leakage or air intake...I still have no pressure showing at psi and the barracuda crawls slow then stops after 5 to 10 minutes. what little pressure there is diminishes to 0. Any suggestions. I have had a pool company guy to the house. He has been here 4 times to assist with some of the above repairs. Greg Domet

User: Inyopools

Marc - I would have another pool man come in and check your pool system again. Sounds like the first one created a suction leak when he serviced your pool system probably around the pump. Even if your pool was operating without a suction leak, your pump may not be large enough to run the suction cleaner with all the suction pipes open. You may have to close the main drain or skimmer partially to get enough pressure to operate the suction cleaner. See our guide on "How To Set Up Pool Diverter Valves for a Basic System + Suction Port" for more information.

User: Marc

Have just bought and moved into our house which has a pool, something that we have wanted for a long time. After a couple of weeks of just my head around how to clean the pool, we got a demo suction cleaner. The pressure wasn't strong enough for it to work effectively.
We have had a guy in to see what is the issue. After cleaning filter and having pump serviced bubbles now appeared from the jets coming into the pool and the auction cleaner doesn't have enough suction to move at all.
Worried what all this may mean, how much it will cost? I hope the previous owners didn't know of any issues.

User: Inyopools

Jen - I'm not clear on the issue. When the "water goes down", is this in the pump's strainer basket? If so, with no pressure, how does the basket fill back up with water, and then repeat the cycle? Did you have this problem before you replaced the skimmer box? In any case, I don't think this is related to your old solar piping. That's on the discharge side of the pump and would show up as a spraying leak. Your issue sounds like a suction problem on the other side of the pump - water going to the pump.
It sounds like you still have a leak somewhere in the suction piping.

User: Jen

We were told by a leak detector that we had a leak at the return pipe join in the skimmer box. We have just finished replacing the skimmer box. The skimmer was around 30 years old and completely surrounded by concrete, we didn't want to have to dig it up again in the future in case of more problems. We topped up the pool and turned on the pump and filter for the first time in just under a year. The problem is the pump is fine for a few seconds and then the water drops right down and the pressure on the filter drops to almost zero till it refills with water again. The pump fills with water again then it drops. While the pool was not in use we had the solar heating removed so we could replace the roof. The solar tubing was old and ineffective so we just threw it away without replacing it. The old pipes are still in place on the side of the house and are still attached to the solar pump so is still a part of the filter and pool pump setup. Could this be the problem?

User: Inyopools

kc - If you are losing water that quickly, it sounds like you may have a major leak, and if you do not see any water spraying out around your pool equipment, the leak may be underground. The first place to check is at your return port that is making a bubbling sound. Generally you could check that by shutting off water to your return ports with a diverter valve. But, if that is your only return, you do not have that option. If you can dig behind the return port, you might try that. Otherwise you may have to bring in a professional to isolate your problem.

User: kc

Hello, I'm losing water in my pool, and the other day I went outside and was looking around my pool I heard a bubbling sound it was coming out of the return jet. I have an old pool with one jet 35x15 9ft deep. the level of the water goes down quickly and the water level is now at the level of the return jet. can you help me very concern person...kc

User: Inyopools

Zman - I'm sorry but we don't have an easy or even moderately easy solution to finding and correcting an underground leak. Check with the local pool professionals. They may have developed some cost effective approaches recently.

User: Zman

I found the jets in my spa ejecting some soil ,and spa level go down once pump stops,i think i have a leak at the underground return pipe to spa,check valve looks fine,
any recommendations how to find the leak with out digging underground the whole distance from filter to spa?
leak detectors charge an arm and leg just to find the leak,and i think they will ask for a lot to dig underground .
please help

User: Inyopools

John - I haven't seen anything like this. Sounds like some seal is failing under higher pressure, but then I can't explain why it wouldn't fail when you put 40 lbs pressure into the system. Could it be vibration? Is the pump moving around during operation? Is there a crack in the pump housing or around any of the suction fittings? You may have to have a local pool professional come in to look at this.

User: Inyopools

macpet - It is common to see air bubbles coming out of the return jets when the pump is first turned on. As the pump primes, it has to purge any air in the system that collected in the pipes while the pump was off.

User: macpet

Hi I had my pump and filer replaced in May and everything was working fine. I have now just notices when the systme starts air bubles at the return jets (both of them). Do not notice bubbles any other time. No air in any of the areas in the pump/filter system that I can see. Any suggestions? thank you

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