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

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

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

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

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

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 (1 to 40 of 291)

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User: Inyopools

Fulk - I don't know what impeller backspin is. A pool motor can only spin one way by design. And where did the metal shavings from the threaded area of the impeller come from? Something wasn't working right on this new motor/impeller. And I would still spread shaving cream around the strainer lid to see exactly where the suction leak is and to show that it was not corrected by installing a new O-ring. This installer is not going to replace this motor. Get another pool man that will work with you.

User: Fulk

The pool guy came back out, took apart the motor and said the impeller backspun, cleaned outsome small metal shavings from the threaded area of the impeller where it goes on the shaft, put it all back together and turned it on. He absolutely will not submit for a new unit and swears the air leak is coming from the skimmer line even after i showed him the "dents" where the lid sits and told him about the hand soap getting sucket in under the lid making bubbles in the hair trap basket when i tested for a leak. Home warranty is giving us the run around along with this guy. He wants to put stop leak in the skimmer line.

User: Inyopools

Fulk - Sounds like you have a bad "new" motor. Hopefully, the pop and humming of the motor is only a failed capacitor. To see what's involved in replacing a capacitor, see our guide on "How To Replace a Pool Pump Capacitor". To verify leaks around the strainer cover, try spreading shaving cream around the edge of the cover. You will confirm better when the suction leaks are and whether or not you can fix them. From your description, you may have a damaged motor with dents around the cover seal that the O-ring won't seal. And you already know this, but you need a new pool repair man.

User: Fulk

So turned on the pump, heard a loud pop and now the "new" motor just hums.....

User: FULK

Did a hand soap "test" around the strainer lid and am pretty sure this is where the suction leak is coming from. The soap was sucked in along the edge of the lid at several different places. I shut the pump off, opened the lid and had some suds inside the basket.....I also looked and felt around the edge and there are about 3 spots that look and feel like they are dented right where the O ring and lid make contact with it...

User: Fulk

Pool Service guy came out, would NEVER recommend his company to anyone, very undependable. Said the motor was bad but didn't check anything else. 3 days later he replaced it. Turned it on and decided to check the impeller and said it and the brass seal were bad as well. Had to order the impellor and seal but the "new" motor ran fine. After he replaced the motor every time we shut the pump off a "burp" of water would splash out from under the hair trap lid which it never did before. There is a new O ring on the lid also. It took the guy 2 more weeks to get the parts and come back out to put them in. He threw in a handful of granular chlorine, said it should help (water was shamrock green from algae) said he had other things to do and left. Took a total of a month just to get the motor and parts replaced. Everything worked great, had 20-25psi even while vacuuming and no bubbles for 2 DAYS! Now you can hear the "new" motor making a "pulsating" sound like the old one did, strong and then weak and the pressure is flucuating again between 0-15 and bubbles are horrible in the hair trap and return jets just like before! He did not check any of the plumbing to or from the pump for leaks. We are so frustrated and don't know what else to do. I imagine there is an air leak in the plumbing above ground somewhere but am confused about the pump issue. Is it possible its a bad pump or one with a hairline crack in the cast iron?......any suggestions?

User: Inyopools

Brad - You may have leaks in your cleaner hose or its connections. Hold the sections of hose that float on the top of the pool under water. If the stops loss of prime, you have a leak in one of those sections. Take one section out at a time to isolate the leaky section. If that doesn't work, check the section of hose that is going into the skimmer for leaks. If possible, submerge the hose below the water surface at the skimmer. Make sure the skimmer bucket is full of water so that air isn't getting into the system.

User: Inyopools

Nick - See our guide on "How To Prevent DE Filter Powder Returning to Pool" for possible causes and solutions of DE going into the pool.

User: Inyopools

mpives58 - You still may be getting air sucked into your system on the suction side of your pump. A couple of thoughts. Did the tradesmen work near any of the underground suction pipes (assuming you have an in-ground pool)? Could they have loosened one of the joints? Thought two. Do you still have bubbles, if your run without the cleaner vacuum plate installed - e.g. without using the cleaner? If not, you may have a leak in one of the cleaner hoses or the plate. Is the plate completely under water? To test for a leaking hose, try holding all the hoses under water when the cleaner is operating.

User: Brad

Great site guys! I have a Pentair diverter to allow my inground pool to filer via the skimmer or the drain or both. When it is filtering via the drain, skimmer or both there are no issues. Only when I attempt to vacuum via the skimmer air is introduced into the pump and I loose suction. Any suggestions?

User: Nick

Hen my filter turns off de is backing up into pool by main drain

User: mpives58

I have had problem with air bubbles seen at pool pump basket for a little while. It seems to coincide with tradesmen work recently done where localised excavation and fencing was done. I had a pool man come and check the system and he changed pump suction O Rings and e pump basket O Ring seals. He said the problem was better but I still see a big drop in water level in pump basket when cleaner is fitted and air in the top of basket. Recently another pool man came and checked and said the automatic valve in line with cleaner hose and skimmer box vacuum plate was sticking shut causing too much suction at cleaner head. Once this was unstuck the cleaner works better but there is still air at the pump basket but not as much. I spoke to the pool man and asked him if I have an air leak anywhere and he said the pump may be cavitating but I don't understand what this means. I have spent money trying to fix a problem but am getting confused by the outcomes so far. What can I do?

User: Inyopools

jeff - Check your new gasket and lid first. I always go back to my last repair to resolve a problem. Then here's a link to our guide on "How to Correct Low Water Pressure in Your Pool System". It may help resolve your problem. Check for a clogged impeller first. That is a common problem with low water pressure.

User: jeff

replaced lid and gasket on hayward superpump after an hour or so air bubble shoes up and skimmer suction drastically decreases as does return output

User: Inyopools

Frustrated in KS - Is this an in-ground or an above ground pool. If in-ground, did you buy an above ground pool pump instead of an in-ground pump? An AG pump has to be installed below the pool to have gravity dump water into the pump. It cannot suck water up above the pool to prime the pump.

User: Frustrated in KS

Had to replace the pump since the old one decided it wasn't going to work when we started opening the pool. Put everything back together and now can't get it to prime. Tried all the troubleshooting techniques mentioned and can't find a leak. Could it be the pump?

User: Inyopools

Brian - It is normal in most pool systems for some of the water to drain back into the pool when the pump is shut off. It normally takes 1-2 minutes for the pump to prime when it is restarted.

User: Inyopools

Denise – You may have low water flow due to a clogged pump impeller. See our guide on "How To Clean Out a Pool Pump Impeller".

User: Inyopools

tired of failure - You are right. Air would not be coming in from the broken filter gauge. It would be squirting water. Check for the obvious suction side air leaks listed in this guide.

User: Brian

I noticed that when my pump is off that air gets into my motor basket and the motor loses its prime. Does this mean there is a leak somewhere?

User: Brian

When I start my pool pump after its been off for a while I notice that the water level in the pool motor is low and no longer primed. does this mean I have a leak somewhere?

User: Denise

Please tell me what I should do. Inground pool with 3 jets, and air is coming out of only 1 jet. The basket near the filter shows no air bubbles at all. When the pump is turned off, I completely lose prime. Same happens after backwashing. To get the system to fill up, I have to dump a bucket of water into the basket near the filter and then clamp down the top. What do you recommend? Thank you so much

User: tired of failure

My pump box is pulling in a lot of air. I noticed the sand filter gage is broken. Can this cause air to be pulled in to the pump box or would it have to be on the other side of the pump?

User: Inyopools

Randy – Sounds like you have most of the bases covered. I’d return back to the original inground suction leak to see if the repair has broken loose.

User: Inyopools

Low water at skimmer – I think you are seeing the air bubble that had collected in the system when the water was low. They should be reduced significantly after the pump has run about 5 minutes.

User: Randy

First off I want to say thank you for this wonderful site. So I recently had a leak detection company come out and fix an inground suction leak. The pool is working great for a few weeks but then I noticed a lot of air bubbles in the return line and in the pump basket. I replace the pump lid over ring and the plug O-rings and I do not have any unions or diverter valves before the pump. If I prime the pump and turn it off it stays primed and never loses water. But when the pump turns on even on the lowest speed it starts drawing air bubbles. Any help would be greatly appreciated thank you.


the water got a little too low into my skimmer, now i have airbubbles coming out of the return. i have filled the water back up to the optimimum level how do i fix the airbubbles now?
I read nothing on this I turn off the pump? it should be a simple solution

User: Inyopools

confused - It sounds like you may have a blockage in the system. Some of the most common: a clogged impeller in the pump, a toy that has passed through the skimmer when you were cleaning out the basket and is stuck in the first elbow underground, a "clean" cartridge filter clogged with oils and chemicals, and a sand filter with clogged/broken laterals or standpipe. See our how to guides to correct these problems.

User: confused

I have very low pressure coming out of my jet. i replaced the pump but same thing. There are no air bubbles coming out of the jet? no leaks as far as I can see.
could there be a critter in one of the lines?.....i need help here!!

User: Inyopools

Fulk - Sounds like you may have several problems. If you are losing prime when the vacuum is running, you may have an air leak in the vacuum hose. Try holding all of the hose under water. If that stops your pump losing prime, you probably have a broken connection in one of the hose connections. Then pull the motor out of the pump to check for debris inside the pump. Also, replace the motor's capacitor. That may solve your startup issue. We have how-to guides on all these procedures. Just type in "how to" and the information you are looking for, into our search field.

User: Fulk

We have bubbles coming from the return jets and you can see air/bubbles thru the lid of the hair trap when the water is circulating. The pressure on the filter gauge flucuates from 0 -10. If we plug in the va uum hose we lose all pressure and prime, both. We have changed the O rings on both lids, checked the other O rings ( 2 small ones still need replaced)and unions, tried your technique for cleaning the impeller, got nothing but can not pinpoint the issue. The pump is old (we just bought the house) and hums when you turn it on so we have to twist the shaft to help it start and while it runs the vacuum seems to fade from strong to weak or like it pulses..We have not checked the shaft seal, difuser or taken out the impeller to check..any suggestions? The previous owners did switch from a sand filter yo a cartridge one and disconnected or capped the main drain so that isnt an option.....Help!

User: Inyopools

Cecilia - I can not tell what's going on here. I would need more information. Please call our service reps at 877-372-6038 for additional help. If you'd like to talk to someone in Spanish, ask for Hector.

User: Cecilia

HELP! I have the automatic vacuum cleaner in my pool. Every time when the filter is on (5 hours per day), the vacuum will be cleaning the bottom of the pool automatically. For the past week or so, every time, when the filter turns on, I noticed the basket linked to the vacuum cleaner is popping up above the water. (It should be under water). And I can hear there is air leak. The basket usually fills up with water, but when the filter is on, the basket becomes empty. Since my pool automatically adjusts water level, water has been leaking as long as the filter is on. Would you be able to help and let me know what exact I should do? Is there a leak on the vacuum itself? Do I must have the vacuum in order to have the pool function properly? I have pool guy coming every week, I was thinking if the leak is from the vacuum or anything attached to it, I may just remove the vacuum altogether. Suggestions? Thanks a lot!

User: Inyopools

Hank - You may well have a leak in the pipes coming back from the main drain. During the winter, the ground can shift around the pipes and if the joints are not solid, one of them may separate. You will probably have to have a professional come in to look at your underground pipes.

User: Hank

I am getting a lot of air in my system, but no air when I turn off the main drain and just circulate from the skimmer.
Is this the serious leak in the underground main line problem? Is this caused by incorrect winterizing? I live in MA.

User: Inyopools

Very low pressure - If the water is just dripping slowly out of the discharge end of the pump, that probably is not your problem. Try removing your filter cartridge and running it without a filter. If that dramatically improves your flow, you need a new cartridge. Cartridges that are clogged with oil and chemicals may look clean but aren't. If you have a sand filter, try running in "recirculate" mode to bypass the filter. If that helps, replace the sand. If your filter is good, you may have a suction leak somewhere in the front end of the pump. May be causing backpressure in the filter.


I have air bubbles in my discharge side. The port that runs my pool vacuum/sweeper (Polaris) becomes VERY low pressure and won't run my sweeper. If I plug the port with my finger and let pressure build up I get big air pockets and bursts through the port. The pressure will stay god for a little while and then I have to repeat the process because the outward pressure becomes low again. On my discharge side pump there is a white PVC that comes out of the top of my pump at the end, I can see water around the neck where the pump ends and the pipe starts. Could this be the problem?

User: caaldinger

The pop up head on the top step of our pool is creating a whirlpool and air is being sucked into the system. Any idea what is wrong and how I can stop this? It's very noisy!

User: Dennis

I had this problem once and ended having a very small crack in the lid over the filter basket.I replaced the lid and all was well.

User: Inyopools

Luiz - With all that debris you may have a clogged impeller. See our guide on "How To Clean Out a Pool Pump Impeller".

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