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.

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

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 (41 to 80 of 189)

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User: Nick

I found out that there was gunk at the pump impeller, pine needles, seeds, etc that made it past the basket. I had huge air bubbles from one return, no flow from the other, hardly any flow through skimmer, and hardly any water in the pump basket visible through the glass disc.

I removed the basket and reached into the port to the impeller. Lots of needles and gunk kinda stuck to the edge. Hard to get out with my fingers, needle nose pliers might be best, I had misplaced mine. I tried shop vac. If need be again, I might try the blower function from the impeller outlet after removing the hose going to the filter.

What worked this time was reached in from the basket port to the pump impeller with a screwdriver and scraping the sides. I removed 2-3 clumps of gunk. Now the returns are strong, still some small bubbles that I will bleed at the filter or replace the basket o-ring, but great flow everywhere, and major splashage in the basket.

User: Inyopools

Melissa - If you have opened and closed your filter without cleaning the cartridge and your pressure is still high when you start up again, you probably have a cartridge problem. It may look clean but there may be chemical residue in the folds of the cartridge that isn't rinsing out. Try soaking the cartridge in a TSP solution overnight or replace the cartridge.

User: Inyopools

Scott - If your pump is losing prime or you see a lot of air in your pump's strainer basket, you may have an air leak. Try putting a soapy solution on all the connections between the pump and the pool to see if any soap bubbles are sucked into a leak. If your pump is not losing prime, you may have back pressure building up in the filter. Many filters have a breather tube going up the center of the filter. Make sure that is not clogged.

User: Melissa

My pool filter pressure goes from 10 to 30 after I vacuum the pool. We keep cleaning it out, and that lowers the pressure, but honestly, the cartridges weren't dirty. I suspect an air leak as I have seen air bubbles in the filter basket, but can't find it. I thought opening the air relief valve on top of the filter and repricing the system would lower the pressure, but oddly enough, it didn't. Any ideas?

User: Scott "what am I missing?"

Pump is losing pressure. Here what we have done.

Relocated filter. I ran all new PVC plumbing with all brand new unions and o-rings.

Brand new multi-port.

Pump would start and we would have great pressure, but it would slow to a dribble in about 1/2 hour.

Could not get a pool tech out so they talked me through on the phone. I need a new pump.

Replaced pump and worked great for about an hour then lost pressure again. Friend told us perhaps too much sand in hayward s-filter so I removed about 30-40lbs of the 200 I put in.

Same result. I have tried everything and replaced everything. What am I missing.

Could it be air leak in the new plumbing?

User: teresa

Thank u so very much for your how to page, it was perfect. Simple so every one can under stand. Imean every one...since I am a wife of a truck driver I try to do as many of the repairs as I can so my hubby doesent have a million things to do whe he come home for 1 day.. Thank u again so much..

User: Inyopools

Russell - Sounds like your filter is clogged. If you didn't change your sand after the algae problem, I would do that now.

User: Chris

Thanks for the advice Inyopools. I corrected the problem, my pool tech was convinced it was an under ground pipe air leak. I knew it was not. It started after they replaced my pump with a new pump. It actually was my Stingl SR-500 safty vacume switch sucking in air from inside the box.. i noticed when stopping the pump with the off switch from thr Stingl box, I was hearing air realeasing from the box. It was the air hose that goes from the pump to the Stingl box...

User: Russell

We have an 18ft above ground pool. the return pressure gradually decreases and only improves after a backwash. I have to do this every other day. Pump and motor were new last summer, sand filter is 6 years old. I cannot see any air bubbles in the return water or in the pump basket. Any suggestions would be appreciated. this problem began 2 years ago and about the same time we had a mustard algae problem.

User: Inyopools

Chris - You have a suction leak somewhere between your pump and pool. Try putting a soapy water solution on all the connections between the pump and pool and check if you can see any bubbles getting sucked into a leak.

User: Chris

Just got a new hayward 1 1/2 HP pump replaced on my in ground pool, the old hayward was leaking water at the seal,& and pump was real loud. Pool was filtering fine and no air bubbles were present in filter pump skimmer or pool. Now with new pump i have air bubbles in all return jets and in pump skimmer, And with system closed down i lose prime. System operates with a Stingl vac presure monitor? I have closed main drains and bubbles still present in pump window, I have closed skimmer and bubbles still present in returns and pump window as well.

User: wp

We were having significant air bubbles in pump basket and return lines. Replaced all gaskets and pump seal. Found the problem to be one drain plug in the pump basket had some minor debris. Once cleaned, problem solved!

User: Inyopools

tom - If you only get air bubbles when your main drain line is open, it sounds like your problem is in your main drain line. You may have to call a professional to have that pipe looked at.

User: tom

I have air bubbles on the intake side at my pump. when i close the main drain valve, the bubbles stop. shutting off the skimmers, one at a time, doesn't change the problem. i have the pool filled to the max and i'm not loosing any water. the height difference is only 4". i completely covered the patio over where the lines run, with soapy water, no results.. I have used smoke to see any intake on exposed pipe. no results.... any more ideas?

User: Inyopools

pat - You probably lost prime on your pump and damaged your pump motor running it dry overnight. I would take the motor into a local motor shop to check it out, but you are probably going to need a new motor.

User: pat

ive left my baracuda out of the water overnight while still conected to the pump and now the pump has stopped working... what do i do???

User: Inyopools

newbies - If your filter does not have an air relief valve, try opening the filter drain slightly at the bottom of the filter.

User: newbies

Assuming I found the air leak, how do I release the air pressure accumulated in my sand filter? Right now my system reads 20 psi when is off … how do I make that reading going down? filter backwash?? i appreciate the help

User: nibornm1

Great info and steps to follow. Thank you. In my case, I was seeing most bubbles emanating from one inlet and less in the other two. My motor and pump were just a little more noisy than usual. On disassembling the pump I found 2 small (less than 1 inch long) pieces had broken off the 14 year old filter basket and jammed in the vanes of the pump impeller. I will probably put up a photo on Youtube, user name there is nibornm1

User: Inyopools

Julius Yehilomo - It sounds like your pump is not large enough to overcome the 6.5m head of water. Also be aware that there are two kinds of pumps. The ones designed for above ground pools rely on gravity to feed the water into the pump and must be installed below the level of the pool water. You need a suction pump designed for in-ground pools.

User: Julius Yehilomo

sea water pump suction is above 6.5m from deck. It was primp 3 times but still can't suck the water from suction side.

Please need your assistance.

User: Inyopools

Air in pump - Unless you have a check valve before the pump (most systems don't) the water in you system will partially drain back into the pool from the pump and filter. It is normal for the water level in the pump strainer to drop. That's why a pump has to be re-primed each time it starts up.

User: Inyopools

matt - I don't know why shutting off the main drain line would create air in your lines unless shutting one of three lines down puts more suction pressure on the other two lines and pulls more air through a small leak. Try shutting off just the skimmer and see it that generates air also. By shutting off each line one at a time you may be able to isolate your leak to one line.

User: Inyopools

colin - Do you have a diverter valve between the skimmer and the pump? If you shut that off and the bubbles stop, you can potentially isolate your problem to the skimmer or the length of pipe between the skimmer and the diverter valve. Also check around the diverter valve for possible leaks.


I have an issue that sounds different to what most people seem to describing. When my pump is running I have no air in the system at all ( no bubbles in return jets or in the strainer basket...) But when the pump shuts down, after about 4hrs there is a lot of air visible though the clear top of the strainer basket. Where can this air be coming from if it is not entering the system while the system is running? As soon as the pump shuts down I am sure I can hear the water level dropping in the DE filter...

User: matt

i have an air leak in my system. i have three lines leading to my pump. a main drain, a vac and skimmer. when i turn on the main drain, the air leak goes away but i loose suction on my vac line (kreepy krawler weak and doesnt move). when i turn main drain off, i have air in returns with both skimmer and vac open....any thoughts.....thanks matt

User: colin

just started seeing air bubbles coming from only one jet in the pool. from the one closest to the pump. pool is not losing water. any easy way to tell if it is sucking air from the skimmer suction line that runs underground? pump lid has always a a little bit of air in the top, has no removable fittings and have not had the lid off prior to the problem starting...any ideas?

User: Inyopools

Jim P - Assuming that your jets were working and stopped - for some reason water from the pump is not getting to the jets. Do you have an automated diverter valve that controls the flow to the jets? If so, check to see if actuator on top of the valve is stuck closed and is not responding to the open signal.

User: Jim P

I have an in-ground spa/pool combo, Jandy RS6 controller for automatic controls. My spa has 6-jets, five of which blow air - one that is sucking air. I replace the whole motor assembly that generates the whirlpool action in the spa to no avail. So why is it that the 5-jets blow (and not very hard) and one-jet sucks? Please help.

User: Inyopools

Significant Air Leak – I don't know what your diverter valve set up is but look at this one to see if it’s close to what you have: “Typical Diverter Valve Setup for Pool system with a Spa”. The overview picture shows all the diverter valves for the Suction side [before the pump] and the Return side [after the pump]. Air leaks are on the Suction Side so we don't have to look at the Return valves. If you have no leaks when in Spa mode, your leak is not coming from the Spa drain line. Also the leak cannot be in the pump or pump line or you would have air being sucked in when in Spa mode. To isolate your leak open up each of the other suction lines one at a time. Review this diverter valve guide for setting instructions if necessary. First open just the vacuum liner; then just the pool drain; then just the skimmer. You may have to leave the Spa drain open with each of these tests to get enough water flow. This should isolate the problem to one of the three pool suction lines.

User: Inyopools

derek – It sounds like you may have a leak in your vacuum hose. Take the last section of your hose closest to the vacuum port [or skimmer if you are using the skimmer port] and separate it from the rest of the hose. Keep it connected to the port and hold that section of the hose completely under water. If the bubbles stop, you have a leak in the hose sections that lay on top of the water. Check each of the hose joints in the part of the hose that lays on the surface.

User: Significant Air Leak

The filtration system for our in-ground pool has a significant air leak. However, when the valves are turned for spa use, there is no air leak. I have:

1. Checked the jandy intake valve - no damage
2. Checked the skimmer/diverter valve for occlusion - clear
3. Checked for water leaks/spirts on glued connections, pump motor, lint pot lid/gasket, - none present
4. Checked with the magic 8 ball - nothing definitive

I guess I could have a breach in the intake system underground somewhere.


User: derek

I have a issue with air bubbles in my pump but only when I hook up my pool vac. When I do not use my pool vac, the system is air free. Help!


We were having bubbles every time the pump would kick on. We have an in floor cleaner and the bubbles would last for about a cycle of the pop-up heads. There was no bubbles in the pump basket but a small leak around the motor housing. We installed a new variable speed pump and but it is still popping when it kicks on. Not sure where the air is coming from. Any suggestions?

User: Inyopools

Exasperated - I would need more information on your filter to give you more specific answers. In general, first eliminate the possible effect of the cleaner by disconnecting it and running your pump without it. Then, if your filter pressure increases, you know it's not a cleaner issue. Recheck all the joints and O-rings in the pipes to the pump. When you shut off the pump and the filter has back pressure, you may see water briefly squirting out and suction pipe leaks. Correct these leaks. Then, as you pointed out, some filters have a breather tube going up the center of the filter to bleed off air collecting at the top of the filter. See if the top of that tube is clogged.

User: Exasperated

After 10 min my kreepy stops working with air in the pump strainer basket. I replaced all the Kreepy pipes, bypassed the weir-pump pipe, replaced the Kreepy, replaced the sand in the filter. It seems as though there is an increase in air pressure in the filter. Is it possible that it is the mechanism in the filter that returns air to the pool that is not functioning? How does it work and how do you check/repair it?
Thank you for your help.

User: Inyopools

SBMini - Generally when your water level falls below the skimmer, your system sucks in air causing the pump to lose prime and run dry. When that happens, the shaft seal on the motor burns up. If you fill the pool up and restart the motor at that point the shaft seal will leak, spray water on to the motor and eventually short out the motor. If you are not seeing water dripping or flowing out of the bottom of the motor, you must still have a good shaft seal. If your pump and filter are dry, I would guess that your leak started before you got home and was what lowered your pool water level to below the skimmer. Turn your pump off and try placing drops of food coloring around the bottom of the skimmer and the main drain to see if it is sucked into a leak. If you have a leak in an underground pipe, you may have to call in a professional to repair it.

User: SBMini

Our pool level got below the skimmer when we were out of town a last week. Upon returning, there is air in the system and the pressure of the filter is too high. We're going to check/replace the o-rings and the motor seal if necessary this weekend.

However, since returning we've also noticed that we're losing a lot of water. We're adding water ever day to keep it at the appropriate level. Everything around the filter and pump is dry. We aren't sure where we are losing water, but I have to think it is related to the air in the system.

It hasn't been any hotter here than normal that would explain increased evaporation either.

Any thoughts?

User: JeffS

Thanks for the helpful webpage. Just installed a new pump after my 3 year old Hayward Superjunk died. Was getting a lot of air and the solution was in your posts here. When I shut the pump off I was getting a little squirt of water from one of the drain plugs. Reseated the plug and the leak stopped. Thanks again!

User: Inyopools

Simon - A burst of bubbles out the return port on startup is normal. The pump is clearing out any air that's in the system when the pump is off. If you have algae clogging the DE surface, I would recommend backwashing your filter more frequently.

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