How to Identify and Correct Air Leaks

Written by:  Danny Rhodehamel

If you are seeing significant bubbles coming out of your return lines into the pool, you probably have an air leak in your filtration system. Possibles 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 significant 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 pint 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 tight, you may be sucking air around the lid. To check the lid, first TURN OFF POWER TO THE PUMP at the breaker box.

Step 4
pool pump strainer lid

Take off 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 may be in the goove. Check the O-ring for cracks or wear. Sometime 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. 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 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 above, check that this O-ring is not worn of cracked and that it is seated correctly in a clean groove. Lubricate the O-ring. Retape the threads of the union with 2 or 3 layers of Teflon tape and reconnect the union. Hand tighten the union.

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 motor shaft seal. The picture at left shows the location of the motor shaft seal in a cut-away version of a Hayward pump. For instructions on replacing a motor shaft seal go to 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 significant air bubbles coming out of your return lines into your swimming pool, you may have a more major problem like leaks in your underground lines. Call a pool maintenance professional to help you isolate your problem.

Comments (1 to 40 of 228)

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User: Inyopools

Hey Mr. Wilson - Not sure what your pool issue is or where you have a leak. Air leaks occur in suction side of the pump as it is drawing in water from the pool. Pressure or water leaks occur on the discharge side of the pump returning to the pool. Both your heater and filter are on the discharge side of the pump so you would see them as squirts of water. Air leaks on the suction side are sucking in air so will not be as obvious. If your filter band is leaking (dripping, squirting), you should fix it as you indicated. When you replace the band, make sure to hit it lightly with a rubber mallet to make sure it seats evenly all around the band.

User: Hey Mr. Wilson

thanks for the guidance on finding an air leak. I checked them all and the fittings to the heater were loose. I also cleaned the basket gasket and put more sealant and reapplied, thinking that would work. I noticed leaking from the filter band itself. So I guess I need to clean the filter, add DE and then re apply the large ring on the filter to be sure it's not leaking.

You didn't mention that in your helpful hints so I just thought I would say this OR if this can't cause the air leak, to maybe let me know.

Thank you!

User: Inyopools

bogie152 - Thank you for your suggestion to tighten the motor drain plugs. I will incorporate it in this guide.

User: Inyopools

m - Thank you very much for your comment. I will incorporate it into our guide.

User: bogie152

I too had major bubbles coming out of the return lines. I found that the drain plugs FOR (ON) THE PUMP were loose, probably from vibration over the years. I tightened the drain plugs and that took care of the problem

User: m

also check noting is holding up the flap at the skimmer. this may not be obvious at first .

User: Inyopools

AHHHH! - Possible solutions depend on what filter you have. If it is a cartridge filter it may look clean but might be clogged with chemicals and oils that don't wash out. Try cleaning in a TSP solution or buy a new cartridge. If it is a sand filter, you may have a clogged breather tube or it may be time to change the sand (every 5-7 years).

User: AHHHH!

We spent an hour cleaning out our filter last night.. we have a 16x32 inground. and the filter and return started out really strong for like 2 hours, then it gets lower and lower and the pressure in the return is low and there is no suction. I checked the impeller and it seems there is no block.. the pressure gauge says 20 and its so not 20. there are some air bubbles in the return when we first put it on.

User: Inyopools

camp tagi - Thank you for your comment. This may also be a good way to find suction leaks. If you are filling the suction pipe at the skimmer under hose pressure and with the pump off, any leak on the suction side should squirt out instead of sucking in. You might be able to build up more pressure by placing the MPV in a "Closed" position to block off entry into the filter.

User: Inyopools

hatemypoolde - Sorry for the delay in response. We have had system problems too. Some of the common problems that might be affecting you: check to make sure that your impeller is not clogged; make sure you haven't put too much DE in your filter; try opening up your suction lines if you have diverter valves, then check your return lines. You might call Hayward at 866-722-2100 to see if they have any idea why you have to keep bumping your DE filter.

User: camp taji

get a "drain King" It screws on to the end of a garden hose .. put in it to the skimmer line and turn on the water. This will fill the line backwards with water and displace the air... if possible don't drain your system in winter unless there is a freezing potential. The drain king has a rubber bladder that seals off backflow thus making the line fill completely with water.



User: hatemypoolde

We're dying here. We had all kinds of suction problems last year with our above ground 5x24 round pool. We got so sick of it that we didn't even close it at the end of the year. It's July, we've been working on this since April and it's not even close to open. We have replaced everything except the motor which is only two years old. Our filter runs between 20 and 25 psi and the auction and return push does out a few minutes after the pump starts. We have to bump our Hayward EC-50 filter entry two to five minutes. At one point, we got the time up to 20 minutes but then we vacuumed the pool to waste, back washed the filter and the constant bumping started again. We spend ask day everyday working on this stupid pool and we don't seem to be getting any where. Help me understand what is wrong here. High pressure, low suction, low return, no leaks anywhere that we can find.

User: Inyopools

2yz4u - I would expect the pressure to drop at low speed. As long as your water remains clear, your system should be operating correctly.

User: 2yz4u


I have a 12'x20' oval semi-inground. A Hayward Perflex DE filter (2013) & a new (2015) Blue Torrent 2-spd 1 1/2hp pump. The pressure on my filter has been 11 at hi-speed and barely registers a number at low speed. There are some bubbles coming out of the return, but the flow is sufficient (at low speed).

When the pressure is so low (3-5psi) is the filter still cleaning the water in the pool? The new pump was just installed (6/24/15) and the water clarity is crystal clear.

User: Inyopools

Poollady - First check of air leaks in the connections between the pool and the front end of the pump. Water may squirt out from backpressure when you turn the pump off. Then check your pump's impeller to see if it is clogged. See "How To Clean Out a Pool Pump Impeller". If that look good, pull the motor out of the pump housing and see if the impeller is loose or broken.

User: Poollady

I have 4 water inlets 3 have air bubbles and one does not, trying to track my problem. I think it could be within the pump impellar, what can I check?

User: Inyopools

Flyinghigh - Most filters have a breather tube going from the top of the tank to the bottom to release any air that is trapped in the top of the tank. Make sure that tube and the screen at the top are free of debris. Dumping a little extra Algaecide, would not cause this problem. Also check for small air leaks in the suction side of the pump by temporarily pasting the connections with plumber's putty.

User: Flyinghigh

my pool opened up with no problems. Just a few days ago, I would shut down the pump and get that massive rush of backwash back into the skimmer basket followed by the skimmer lid popping off, etc. Turn it back on, and takes several seconds for the pump to re-prime itsel. After some troubleshooting, the severe bsckflush occurs with the Hayward XL Valve lever in filter ONLY. It does not do this backflush in recirculate or any other function. The pump even holds a prime with the lever in recirculate. I've checked the pump lid seal, with no difficiencies noted, followed by all pipe junctions screwed on tight, etc.

Any help would be appreciated! My initial guess would be the Hayward XL valve needs replacing. I also dumped a little extra Algaecide in the pool by accident. Could this be it?

User: Inyopools

Ranick - If you only see bubble when you first turn the pump on, that's normal. If you had a suction leak you would have air in your pump basket so that evidently isn't your problem. Try closing down the return jet diverter valve a little to balance the system. If your pressure is low, see our guide on "How To Correct Low Water Pressure in Your Pool System". Check your impeller to make sure it isn't partially clogged.

User: Inyopools

bmcg - Here's is a guide that shows you some of the common causes of low pressure: "How To Correct Low Water Pressure in Your Pool System". A clogged impeller [#6] is one of the most common.

User: Ranick

Pool is less then a year old. Had to fire the contractor so no warranty. Need help with this. The pump basket has no air in it but yet there are bubbles coming out of the return jets. Pool is a 18 x 36 with a 1.5 hp pump. Any ideas?

User: bmcg

I have a rod system using diatomite seeing constant low pressure out of my pool jet. pressure out of the filter into the heater seems fine, but then something is losing pressure between the heater and the jet.

User: Inyopools

needtoswim - If the bubbles only occur for a couple of minutes when you first turn the pump on, that's normal. Otherwise you may have a suction leak. Try putting plumber's putty temporarily around the outside of each of your suction connections. If the bubbles stop. look at the last connection puttied for your leak.

User: needtoswim

Just put in a new liner, pump and filter - filled pool and turned it on and I still am receiving bubbles in the waste basket as well as the return flow into the pool - seems like a leak but were? i would be appreciated any info on this

User: Inyopools

low pressure - First replace the gauge. It may be bad. If a neighbor has one like yours, you could swap it out to see if that is the problem. Then I would look at the pump. Is it fully primed - water completely fills the basket. If not, check the connections before the pump for air leaks. Then check if the pump's impeller is clogged. See our guide on "How To Clean Out a Pool Pump Impeller".


I have above ground 17 x 52 Summer Escape I had a Hayward sand filter pump put on by someone but the gauge never says more than 0-1 psi ever since put on. Just been on about 1 week. Pressure was pretty good at first but now weak again. He never had done hook up before, he usually works with inground pool. I am not for sure he put water in sand filter before adding sand. What could be wrong with weak flow?

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.

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