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 253)

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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?

User: Inyopools

Joeyo - I'm not sure what you are asking. If you are trying to get water out of an above ground pool and you don't have a waste line, try this. Fill a garden hose full of water. Then, holding each end closed, place one end in the pool and trail the other end outside the pool down a slope. Gravity on the water in the hose will suck water out of your pool.

User: Joeyo

Pool water level won't go down ,not evaporating..any ideas

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.

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