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 (41 to 80 of 310)

Add Comment

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".

User: Luiz

I have a jandy 2 speed pump. It had been running normal until 2 days ago. Pool had turned green, i used the leaf master and then brushed the pool. It got late and instead of running the filter and picking up all debris I decided to shut system off and wait until next day to open and clean the filter and then run it. Since then, I have not been able to get any suction in my pump. I've replaced the oring on the pump lid, checked valves to be open. I used a pressure bladder from the pump back to pool and it takes all the water, but then put buckets in pump and try to prime with no luck. Can it be that all 3 lines (2 from skimmers and main drain) got clogged at the same time? How do I know if the pump is just not sucking?

User: Inyopools

Perry - Sounds like your possible air leaks are in the suction side pool piping. Check for air leaks around all unions or other connectors between the pool and the pump. Also check the O-rings in the stems of the pool diverter valves. Check the connection at the bottom of the skimmer. This sometimes separates with the shifting of the pool over time.

User: Perry

I continue to have air getting into the pool after I have replaced all of my gaskets on valves in the suction side of the pool. I have also done a check by shutting off the valves to the main line and the skimmer lines to see if I could isolate the issue that way and the bubbles are still there. When I change from pool to Spa Mode the bubbles go away (there is an automatic valve that shuts off flow from the pool so the water circulates only in the spa). When I return back to the pool mode they come back after a delay of 5 to 10 minutes. I don't understand what can cause the air to enter into the line after a delay. I have a Jandy SHPF pump and Jandy never lube valves. Any ideas would be appreciated.

User: Inyopools

Avilasx5 - It sounds like your system is generating backpressure. You may have too much DE in your filter or your filter's breather tube may be blocked. See our blog on "How Do I Correct Low Water Pressure" Go to the second part on "Causes of Low Water Flow Due to High System Pressure".

User: Avilasx5

Pool equip Sta-Rite S8D110 DE filter filters replaced 3yrs ago
Pump-Hayward SP2302VSP just purchased, it replaced a 1.5hp maxiglas2.
Filters have been cleaned. New kreepy krauly replaced a G4.
Vac runs for about 10-15 min moving along fine then slows to a crawl then stops. Pressure when running fine @ 12psi on gauge, then 20 when vac stops. I then backflush filter and while backflushing vac takes off running again. Any help would be greatly appreciated thanks

User: Inyopools

Peterh - If your sand filter has a breather tube going from the top of the tank to the bottom, it may be clogged causing air pressure to back up in the top of the filter. See out guide on "How to Reduce High Pressure in Your Pool System" to correct this possible issue and explore others related high pressure problems.

User: Peterh

I have a waterco pump and sand filter every time the pump switches off it blows the water our of the filter, pump and lines back to the skimmer box. It evens blows the skimmer basket out of its position. If I backwash and rinse it is good for one operation cycle then goes back to the same issue. When the pump re-starts it takes a long time to get water into the pump & filter system and it blows heaps of bubbles into the pool. Have checked all external connections without digging up piping so far. Any suggestions would be appreciated

User: Inyopools

Sid - You may have low water pressure in your whole system. See our guide on "How to Correct Low Water Pressure in Your Pool System". Check for a clogged impeller first. That is a common problem.

User: Sid

I have low pressure in my automatic pool vac, it moves very slow. I recently got a variable speed pump to replace my old one. I have it set to 30 psi (filter reading), to at least get some water movement through the filter. The pump intake water pressure is very low and the water does not fill the basket area. It's less than half. Not sure if I have a leak in the system, don't see any visible leaks and pool water level is not dropping

User: Lionel

Thanks very much.!!!

User: Inyopools

Julie - Can you shut off the water to the filter then after the filter to see which way the water is draining when the pump is off. Then concentrate on finding problems in lines before or after the filter. Where is your current check valve before or after the filter. Most are after. If water is draining back into the pool through the pump, you might consider putting a check valve in the line before the pump.

User: Inyopools

Thomas - Bearings can be tricky to replace. If they are not lined up correctly, they can cause drag on the motor and end up overheating the motor and tripping the override protector. Does your motor feel extremely hot when it shuts off?

User: Julie

HELP! When the pool turns off at night the filter "gurgles" all night. Sounds like water is leaving (or air is getting in?) We had someone come out and were told it was probably the check valve. We replaced it yesterday and last night it seemed worse!! No one seems to be able to help us. The filter is right outside our bedroom window so we ran the pool all night instead of listening to it gurgle. Any suggestions??

User: Thomas

I have a variable speed motor (A O Smith) It has a prime mode when the pump starts. Pumps fine no bubbles at outlets at the end of the prime mode it says prime fault. Worked fine till I replaced the bearings. Runs great just won't continue runing

User: Kelly

Simply the best on-line information site! Probably saved me hundreds possibly even $1000 in repair bills. Thank you

User: Inyopools

Airhead - Check around the discharge side of the pump for obvious water leaks, spraying, when the pump is on. I would think it would have to be a significant spray to allow the filter to drain. If this is a new system, water can drain out of the filter if it is installed somewhat higher than the pool water level.

User: Airhead

After the pump has been off for a bit (overnight), the filter has to refill with water. I've replaced spider gasket, filter gasket, pressure gauge. I noticed dampness around the bottom of the filter, no noticeable puddles though. Could a worn o-ring around on the drain plug allow enough water to leak/air to enter filter to cause this problem. Fix??

User: Inyopools

Louvis - If your sixth return port never worked since you purchased your pool/spa, I would guess that it was assembled incorrectly at the factory. Give us a call at 877-372-6038 and we can help you get this corrected. If it was working an recently stopped, you probably have a blockage in the system that would have to be blown out. The water lose may be due to evaporation or you have a slow leak somewhere in the system. Check to see if you can locate where water might be dripping out. Shut the pump off and drip some food coloring around possible areas like the skimmer base.

User: Louvis

I have a brand-new 8000 gallon pool /spa first problem one of the six returns is not working there is no circulation at the eyeball I even unscrewed the eyeball and stuck a Rod in there to see if it was clogged up but this did not correct the problem. Secondly my pool loses water volume when the pump is running basically it is 30 days old and everything is brand-new

User: Inyopools

Psykosoma - It sounds like water in the pipes (before the pump), is draining back in the pool after you shut off the pump. This can happen for a number of reasons not related to air leaks - like the pump being elevated above the pool surface. You may have to add water to the pump basket whenever you have to start the pump up or some people add a check valve between the pump and the suction inlets to keep the water from draining out when the pump is turned off.

User: Psykosoma

Hi. Hoping you can help. I have a Hayward Superpump that is having a problem self priming. It works fine once I fill the basket with water, but once the pump is shut off, I see a small amount of bubbles coming from the pool side inlet in the pump basket. After some time, if the pump is turned on again, it will not prime itself. I assume its an air leak on the suction side since that's where the air bubbles are coming from. I replaced the gaskets from the lid as well as the 2 gaskets between the motor and pump. Any ideas?

    1     2     3     4     5     6     7     8    

Back To Top

Please Note:

Inyo Pool Products is not responsible for any injury or damaged equipment
while using our guides. Using our guides is doing so at your own risk.
These guides are suggested use of your pool or spa equipment and may vary
depending on which product you are using.