How to Identify and Correct Air Leaks

WRITTEN BY:  Inyo Pools

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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.


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. Reconnect the union and tighten it 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.


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Inyopools  Posted: 09/19/2017 12:12 PM  Latest Inyo Product Specialist

Andrewbic - When you re-piped everything, did that include the pipe from the skimmer to the pump, so we know there is no clog there? Can you shut off the second skimmer so you know you are only running with the good line?  Then recheck each step in this procedure to make sure each is addressed.  If that doesn't work, buy a GOKIT for your pump and replace all the gaskets/seals.

Inyopools  Posted: 09/19/2017 11:43 AM  Latest Inyo Product Specialist

rrrod09 - I don't understand how you are seeing air in the return jets if your pump won't prime and is not moving water (or air) to the returns. If you have a priming problem, see our guide on "How To Prime a Pool Pump". Also, check that that your pump's impeller is not clogged. See our guide on "How To Clean Out a Pool Pump Impeller".

Andrewbic  Posted: 09/17/2017 18:32 PM  Latest

Thanks. I checked the propeller and diffuser. I have pics of both Both looked well. I also used a drain king on each side of the skimmer line. I didn't see a lot of action like I expected when I ran the drain from the pump back the skimmer. I checked all Jandy valves. Even saw water running back to the pump when I ran the water from the skimmer to the pump. Finally I repiped everything and checked for leakes. So far nothing I then lubricanted the o-ring on the lid and replaced my gauge. Still the same. No suction on the skimmer side? What else could it be??

Inyopools  Posted: 09/17/2017 13:07 PM  Latest Inyo Product Specialist

Keboss - It sounds like you may have a leak in one of your cleaner hose sections. Try holding your cleaner hose completely underwater while the pump is on to see if your pump can maintain prime. If so, pull out each section of hose one at a time to see which is leaking.

Inyopools  Posted: 09/17/2017 12:02 PM  Latest Inyo Product Specialist

Andrewbic - When you were vacuuming all that debris, you may have clogged your pump's impeller. See our guide on "How To Clean Out a Pool Pump Impeller".

rrrod09  Posted: 09/16/2017 18:16 PM  Latest

I have significant air in my return jets into my pool. I've primed it with no doesn't matter if I have the main drain on or the scimmer line on...any advise?

Keboss  Posted: 09/16/2017 16:34 PM  Latest

I have an in ground pool. Everything is fine until I hook up the hose to sweep the bottom. Then I start to get air in the line and I start to lose my prime. I don't lose the prime completely unless I switch to full skimmer. Again with no hose attached in the skimmer I never lose the prime even on full skimmer. Any suggestions on my problem? My guess is I have I leak inground somewhere.

Andrewbic  Posted: 09/14/2017 20:55 PM 

After Hurricane Irma drained some water out while pulling debris and leaves out. My hope was to brush the sides and floor, vacuum, clean filter and add chemicals and fresh water. While I was vacuuming I noticed the debris was too much. I stopped and tried to start draining more and pick up debris with net. Draining was slow. Then suction from the skimmer was gone. Checked all handy valves for debris. Check both baskets. Ran a drain bladder from all ports. No clogs. Actually saw the water flowing from each point. Turned it back on and Still no suction at all. Can get flow from the main drain but not enough to fill up the cartridge tank. My focus is on getting suction back. What do you think?

Inyopools  Posted: 08/21/2017 11:15 AM  Inyo Product Specialist

Nmobae - It sounds like your motor isn't priming. See our guide on "How To Prime a Pool Pump".

Inyopools  Posted: 08/20/2017 12:57 PM  Inyo Product Specialist

Stevie70 - Is your pump not priming so you aren't able to get any water flowing through your system? If so, see our guide on "How To Prime a Pool Pump". If you have water flowing through your system but it is very weak, see our guide on "How to Correct Low Water Pressure in Your Pool System". Check for a clogged impeller first.

Nmobae  Posted: 08/19/2017 12:12 PM 

I have a pentair tagelus sand filter on my hot tub and when I checked on it this morning it was running low pressure and leaking from the fittings on either side of the motor. I tightened the fittings and the leaks stopped but now I can't get the filter to start sucking water in. Flow is zero and there is no water entering the housing before the motor. Any suggestions on issue/possible fix?

Stevie70  Posted: 08/15/2017 7:44 AM 

I have a brand new pool/cartridge filter. Air pressure is 0 psi, return water into pool has no pressure. Checked the skimmer and pump for clogging, it is not. do you turn off valve on skimmer basket? Two what else can I cjeck?

Inyopools  Posted: 08/05/2017 13:37 PM  Inyo Product Specialist

Anonymous (air in filter) - From your description, it sounds like you have a suction air leak in or before the pump. The filter is after the pump. If you had a leak in the filter, it would be a pressure leak and you would see water squirting out at that point. Suction leaks are sometimes had to find. Try blow smoke around the front of the pump and at any connection between the pump and the skimmer. If you have a suction leak, you should see the smoke being sucked into the system.

Anonymous  Posted: 08/02/2017 18:06 PM 

Hi there, I have air constantly building up in my sand filter and then coming out of my return lines in my pool, I have replaced the multi port valve, orings, checked for leaks and can't isolate the problem- it's drawing me to think it's either the sand filter or intake line.. the pump primes very well and there is no evidence of bubbles after you backwash but it builds up over a small period of time.. if it was the intake line being cracked would I be loosing water or how do I check that it's the sand filter casing me issues as my last resort is to replace the intake line ...

Inyopools  Posted: 07/31/2017 15:01 PM  Inyo Product Specialist

bere1229 - With an above ground pool, the pump is below the surface of the pool so water automatically flows to the pump by gravity. When you turn the pump on, was there a humming noise? If so, you may have a bad capacitor. See our guide on "How To Replace a Pool Pump Capacitor". Also, see our guide on "How To Troubleshoot a Pool Pump Motor - Motor Fails to Start".

Inyopools  Posted: 07/30/2017 12:31 PM  Inyo Product Specialist

Bpgraves - Sounds like you have the same problem as the previous person. Try gently blowing smoke around the front of the pump and suction side connections to see if smoke is drawn into a leak. Also, when your filter is in recirculate or backwash mode, air is not able to collect in the top of the tank as can happen in filter mode.

Inyopools  Posted: 07/30/2017 12:11 PM  Inyo Product Specialist

DE guy with pressure rise problem - When you turn off the pump, do you have a strong surge of water pushing backwards from the filter through the pump and through the skimmer. Or can you lower the psi during operation by opening the pressure relief valve to let trap air out of the top of the tank? If so, you probably have a suction air leak somewhere from the front of the pump back through to the skimmer. Try blowing smoke around the pump and connections before the pump while the pump is operating. If you have a leak, you will see the smoke being sucked into the suction side of the pump.

bere1229  Posted: 07/29/2017 21:28 PM 

I am a novice in pools. Just bought a home that came with an above ground pool and I've been trying to learn everything about maintenance and pool chemistry. Last night I came home to my 18 x 4 ft pool that had drained to about halfway. I ran to the pump and filter and saw that the hose connected from the pump to the filter had split. I had the pump running, so it was running this way for who knows how long. I bought a replacement hose and attached it, filled the pool, and connected the pump but it did not turn on. I imagine there's air in the hoses and pump basket and I don't know how to fix this. Please help! I have a Hayward pump and filter.

Inyopools  Posted: 07/28/2017 11:25 AM  Inyo Product Specialist

Pieter - It doesn't take much of an air leak to cause significant bubbles and generally these air leaks come for the suction side of your pool at or before the pump. From your description, it sounds like you may have a suction leak in your pool cleaner hose. Try holding the entire hose under water to see if that stops the increase on air in your strainer basket. If so, check for leaks in the folds of your cleaner hose or the hose connections.

Bpgraves  Posted: 07/26/2017 14:56 PM 

I have a problem with air in my returns. When the pump cuts off all of the water surges back into the pool. Air is getting in the system somehow. This doesn't happen when the valve is set on recirculate or backwash only in the filter mode.

DE guy with pressure rise problem  Posted: 07/26/2017 11:03 AM 

DE filter pressure rising ~10 PSI in only 4-5 hours of operations. Have been trying everything for last 6 weeks...backflushing, new DE put in, even new filter grids, thinking the old ones were microscopically plugged after TSP and acid leaks on input side of pump, breather tube filter operation, bubbles appear in strainer right ahead of pump, and water flow out of filter greatly diminishes after 4-5 hours, along with pressure rise...input seal on pump union is tight, too...have tried every trick on your website here - any other ideas?

Pieter  Posted: 07/26/2017 6:02 AM 

I installed a new pump with a new pool cleaner but still having bubbles. I do see a small leak on the filter seal can this be the cause of the bubbles? Bubbles coming out at return jet and when I open the lid to take out skimmer basket there are also bubbles? How big can the leak be to cause air bubbles? When the pool cleaner is not connected the water under the pump lid is almost to the top but when I connect the pool cleaner the water level drops to half and pool cleaner stop working? Any advice please! Thanks

Inyopools  Posted: 07/18/2017 15:47 PM  Inyo Product Specialist

Anonymous (stuck weir door) - Thank you for your feedback. I will add this solution to this guide.

Inyopools  Posted: 07/18/2017 10:41 AM  Inyo Product Specialist

Mambas - Check your cleaner hoses for leaks in the accordion folds by holding them under water or taking them out one at a time.

Inyopools  Posted: 07/18/2017 10:36 AM  Inyo Product Specialist

Sarbear - Try pulling your motor out of its housing and checking for a clogged impeller. This is a common occurrence.

Inyopools  Posted: 07/18/2017 10:33 AM  Inyo Product Specialist

Murph - Thank you very much for your feedback. It will be very useful to our customers. The stuck weir door on the skimmer has come up before. I will add it to this guide.

Inyopools  Posted: 07/18/2017 10:19 AM  Inyo Product Specialist

Anonymous (return side air leaks) – Thank you for your feedback. As you indicate, air leaks on the return side seem counter to logic. With water under pressure, you would expect a water squirt at that leak not air sucking in. But nothing speaks louder than success, and I have seen a couple of other similar comments on this subject. I'll have to research this more.

Mambas  Posted: 07/17/2017 11:06 AM 

My swimming pool pump work great until I put the kreepy krauly in. Then it sucks air all of a suddenly. What can be the cause?

Sarbear  Posted: 07/16/2017 16:09 PM 

I was vacuuming the pool and small pine ones were sucked up. The pressure dropped and the line was blocked. We ran a hose through the line and the pinecones came out. But now the pump is not getting enough pressure again. We've taken things apart and tried the seals, etc. Not sure what to do now. Was working just fine until this happened.

Anonymous  Posted: 07/16/2017 15:33 PM 

My fluctuating pressure was due to my skimmer flap being stuck in the upright position due to a poor install. I installed the flap correctly and the pressure issue went away.

Murph  Posted: 07/16/2017 10:19 AM 

Sorry, forgot to mention the "door" to the skimmer had been cemented on one side by the reconstruction people, broke it loose and solved that issue. Still have tons of bubbles.

Murph  Posted: 07/16/2017 10:11 AM 

Thank you to all.I tried the suggestions that I knew how to do, then I had a pool company come in and replace some collapsed piping in the shallow skimmer with PVC. I thought that would do it, but he left and I still have bubbles, more than I did. I have a call in for him
and I will show him this site, maybe he can help. Thanks again, I will let you know how it turns out.

Anonymous  Posted: 07/15/2017 10:14 AM 

I just resolved my problem with air bubbles in the returns. I searched for air leaks on different sites and 99% said that air leaks come only from the suction side of the pump. Not true. I did have a pvc joint leak leading to the pump which caused air bubble in the strainer basket of the pump. After fixing this issue there were no bubbles at the pump but still had air bubbles in the returns. I traced my problem to the chlorinator o-ring which had been improperly installed. Mind you, this is on the supply side of the pump. As soon as I properly seated the o-ring in the chlorinator all signs of air bubbles disappeared. Hope this helps.

Anonymous  Posted: 07/13/2017 13:56 PM 

In addition to these excellent suggestions, I have a cutoff valve on the suction side. As a last resort I replaced it. Problem solved. Works like new.

Inyopools  Posted: 07/10/2017 15:00 PM  Inyo Product Specialist

Murph - It sounds like you have a blockage in your front system between the pump and the skimmers/main drain, or you have a significant leak between the inputs and the pump. Some of this could have been from junk collected in your piping since the renovation. Look at your pump's impeller first to see if that is clogged. Then use your diverter valve to isolate the problem to the skimmers or the main drain. If you have a clog in one of these inputs, try blowing it out with an inflatable drain cleaner like Drain King.

Murph  Posted: 07/09/2017 9:29 AM 

I have a Hayward sand filter that I replaced the sand with "zeo" sand last year. My pool 20 X 40 inground pool has 2 skimmers, the shallow one will have a pipe replaced this week when the pool man gets here. It is shut off, and everything has been running fine for 3 weeks since I opened. Yesterday, I started it and 30 seconds later the pump reservoir was dry, the pump was running fine but no water was moving in the skimmer. The jandy valve directing where the water draws from was replaced last year. What else can cause the water not to draw besides a (shudder) underground leak in the deep skimmer/main drain line? I had a complete renovation done this spring, new tile, coping & plaster, could something (loose plaster, debris) have gotten in the main drain?

Inyopools  Posted: 07/03/2017 16:26 PM  Inyo Product Specialist

Faye - See our guide on "How to Correct Low Water Pressure in Your Pool System". Look at Step 6, Clogged Impeller, first. That is a common culprit.

Faye  Posted: 07/02/2017 22:26 PM 

We have changed everything on the inground pool equipment. We have a new 1.5hp motor. New arms for sandfilter and new top for sandfilter that turns for backwash,etc. (don't know technical Name). Replaced sand and we still donot have enough pressure to vacuum bottom. What could possibly be our problem? Please help!

Inyopools  Posted: 06/28/2017 10:17 AM  Inyo Product Specialist

Darrell - It sounds like you have a suction air leak that is causing air to build up in the top of the filter tank. When you press down on the MPV handle, you are opening up the system and letting this air release. Suction air leaks occur in the connections at or before the pump on the suction side of the pump between the pump and the pool. Since the MPV is on the discharge side of the pump, any leak there would show up as a squirt. So concentrate on the suction side of the pump to isolate any suction leaks. Try covering suction side connection with a soapy solution. If it has a leak, you will see soap bubbles being sucked into the hole.

Inyopools  Posted: 06/27/2017 12:53 PM  Inyo Product Specialist

drigs - Your problem sounds the same as "not a problem solver" below. See my comment to him.