How to Identify and Correct Air Leaks

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If you see many 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
  • leaks in the pump seals
The leak source must be identified and corrected for the most efficient pool pump operation.

Video

Step by Step

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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 many 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.

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Step 2

The ideal water level should be at least halfway up the skimmer intake. If the water level drops below that level, the skimmer can gulp air with the ebb and flow of circulating water.This simple problem has a simple fix:
  1. Add water.
  2. Drop in a hose and get that water level up.
  3. Keep an eye on it in the future to prevent a reoccurrence.
A simple add-on feature is water levelers, ensuring your water is always optimal.

Step 3

Before we begin inspecting the plumbing elements, switch off the master breaker to your pool pump.

Release water pressure in the system using the air relief valve on your filter. An air relief is generally only found on Cartridge and DE filters. Sand filters do not have this feature, so expect some to splash when accessing plumbing elements like the pump strainer lid and unions.

Step 4

Pool Pump Strainer Lid O-ring: A single gasket seals the pump strainer lid, which, once it loses pliability, can provide a direct route to foul your prime. Typical signs of wear are cracking in the rubber, warping or stretching, and the obvious missing bits.

Check the rubber gasket for cracks, pinching it into a smaller loop. Cracks will look like striations across the length of the gasket.

Warped or stretched gaskets are evident when the o-ring sits in the groove o-ring, spilling over. The warping of an o-ring can lead to it being pinched, creating a gap through which air can enter the plumbing.

If necessary, replace with the new gasket after cleaning the O-ring’s groove of gunk and leftover lube. Apply a new coat of lube, as well.

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Step 5

Your pump housing’s drain plugs are often overlooked when diagnosing an air leak, but these little gasket-sealed ports cause havoc if the seal is broken. Use any of the air leak techniques mentioned above or do an eye inspection for a pinched or defective gasket.

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Step 6

If your pump strainer gasket wasn’t the issue, move forward to the pump union. Most pumps have a union on their intake, allowing easy maintenance and removal. These unions have a single gasket that seals the cuff and screw-on adapter. Most commonly, these o-rings become pinched. Go through the checks of the o-ring mentioned in the previous step.

Step 7

Another common culprit is PVC plumbing glued joints like tees, elbows, and valve ports. The epoxy sealing these joints can become brittle and wash out over time, allowing air leaks that prevent the removal of all the air from the pump, leading to priming failure. This can create a progressively worse and worse air leak. The suction hose plays a crucial role in the priming process, and leaks in connections can prevent the vacuum necessary for drawing liquid up the suction hose to the pump, further complicating priming efforts.

The smoke, soapy water, or shaving cream method is the standard way of finding these leaks, and repair can be as simple as adding a caulk patch. Or, if you want to ensure a permanent fix, re-piping and gluing will be necessary.

Step 8

If your air leak problem only occurs when you attach your vacuum hose, then the issue may be pinhole-sized leaks in one or multiple hose sections. To find and replace these hose sections:
  1. Disconnect all hose sections
  2. Use tape or plugs to seal the end of each section
  3. Submerge the hose section while looking for any stray air bubbles coming from the body of the hose
Complete this for each hose section; replace the sections with holes.After checking the hose sections, consider performing a 'bucket test' to determine if your pool is losing water due to leaks or simply through evaporation. This simple method involves filling a bucket with pool water, marking the water levels inside the bucket and in the pool, and then comparing the two after a few days. If the pool water level drops more than the water inside the bucket, it's likely you're losing water due to a leak rather than evaporation. This test is great at helping identify whether you have a pool leak or if it is natural evaporation.

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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

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(241 to 280 of 604)

InyoPools Product Specialist  Posted: 5/15/2017 

William - If you have a union on the discharge side of the pump, take the union apart and tighten up the pump discharge fitting. If not, you will have to cut the pipe above the discharge fitting, tighten the fitting and reconnect and glue the cut pipe. See the last half of our guide on "How To Replace a Pool Pump With An Energy Efficient Pool Pump" for cutting and gluing instructions. You only have to make one cut above the discharge fitting.
 Reply

 Posted: 5/13/2017 

Oops - it's the discharge side that is leaking water at the joint with the pump. Do you have DIY guide?
 Reply

 Posted: 5/13/2017 

My pump is losing prime every few seconds. I can see water bubbling from the suction side when the prime comes on. Do you have a DIY guide for replacing the leaky PVC joint at the pump?
 Reply

InyoPools Product Specialist  Posted: 5/10/2017 

Out of ideas - If you only have small bubbles in your returns and the pump primes fine and you have no noticeable bubbles under the strainer cover, I wouldn't be concerned. You may have a very small leak in the suction side, but it will be difficult to find.
 Reply

 Posted: 5/8/2017 

Just opened pool and got the equipment working.i am now noticing that there are small bubbles coming out of my return jets. I have a 24k gallon inground guinite pool with a cartridge pentair pump and filter. I notice that a small amount off air builds up at the top of the filter and when I bleed it out by opening the valve the air bubbles in the return temporarily stop but after 3-4 minutes return again. The pumpnprimes fine and the is no noticeable bubbles in the strainer basket. Also, I tried isolating the skimmer and main drain suction inputs to see if that had any affect. It did not.. air bubbles persist regardless of which intake the pump is drawing from. Any other ideas?? Pool is 4 years old.
 Reply

InyoPools Product Specialist  Posted: 5/2/2017 

Bob – I’d check any connectors on the suction side of the pump including the glued fittings (elbows, unions, valves) for suction leaks. Try brushing a soapy solution on each fitting. If the soapy bubbles are sucked into the connection, you have a suction leak.
 Reply

InyoPools Product Specialist  Posted: 5/2/2017 

Kpenley - Does your pool have blowback from the pump to the skimmer when you turn the pump off? If so, you probably have air building up in the top of the filter that creates back pressure against normal flow. If you have a breather hose running from the top of the tank to the bottom, make sure that hose and the screen cap are clear. Also, if you have air building up in the tank, you must have a suction side leak between the pump and the skimmer. Check the suction side fittings. I would start with the connectors to the new pump.
 Reply

InyoPools Product Specialist  Posted: 5/1/2017 

amada - See if your pump's impeller is clogged. See our guide on "How To Clean Out a Pool Pump Impeller". Also, if you have a breather hose going from the top of the filter tank to the bottom, make sure that hose isn't clogged.
 Reply

 Posted: 4/30/2017 

Air bubbles are coming out of my return jets. I had a lot of air in my strainer basket until I serviced all the o rings. Now I have no air at all in the strainer but still have air in the return jets. When I shut the pump off the water drains from the strainer immediately. Are the pump/motor seals the only remaining cause?
 Reply

 Posted: 4/29/2017 

I have a new pump. New sand in filter. After the pump is running for a few hours the water stops circulating. What causes this?
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 Posted: 4/28/2017 

So my problem is the following. I will tell what I have done already. The pool was dirty green and debris in it pump wasn't working. I replace pump, cleaned filter, used the dolphin to clean. It started working fine but like an hour or so later, I noticed the pressure going up and the water in the pump drainer going down. So it will work for an hour or ok, but then the same thing happens. I was told that the skimmer line might be clogged which I tried to unclogged, but still same result.
 Reply

InyoPools Product Specialist  Posted: 4/27/2017 

steve - No, a defective housing gasket would not cause air bubbles. The gasket is on the discharge or pressure side of the pump. It would produce a squirting water leak when the pump is on.
 Reply

 Posted: 4/26/2017 

Can a defective housing gasket cause air bubbles or will that just cause a water leak?
 Reply

InyoPools Product Specialist  Posted: 4/21/2017 

Dave - In in the basket area is generally due to an air leak at or before the pump. The most common pump leak is due to the strainer cover. Check the strainer cover for cracks and replace the cover if required. Then check the O-ring under the cover for damage. If it is old and stretched. I would replace it.
 Reply

 Posted: 4/19/2017 

My pump basket has a 3-4" air gap between the lid and the water level. The pump is circulating the water well, but I can't seem to get the air out. The water also sounds like it is "sloshing" around as it goes through the heater, but not sure where to look for the air. Any ideas? Thnx.
 Reply

InyoPools Product Specialist  Posted: 4/10/2017 

Collette - You may have drained most of the water in your pipes to the pump. Try adding water through the pump's strainer basket for a couple of minutes to get some water back into these pipes.
 Reply

 Posted: 4/6/2017 

Heavy rain past couple of days so I have to open the valve to release some of the water. After doing so i tried to run my pump but it won't hold the prime. I let air out of the filter but no change. Please help!
 Reply

InyoPools Product Specialist  Posted: 4/4/2017 

dcs - It sounds like you may have a leak in your suction cleaner hose. Try holding the entire hose under water when the cleaner is operating. If that stops the air in the basket, you have a leak in the hose or one of the hose connections.
 Reply

 Posted: 4/3/2017 

had air in basket- water would drain out of basket when i shut the pump off, replaced all o rings water stated staying in the basket, but now there is air in it lots of bubbles when I run the pump, yet water stays in the basket-- I unhooked the pool sweep-- and the air in the basket went away and the pressure went up from 8 to twelve-- what is the problem?
 Reply

InyoPools Product Specialist  Posted: 3/28/2017 

rcholden - It is common for the water level to drop in the strainer basket after the pump is shut off. That's why a pump is primed - to purge the air from the system when the pump is turned back on. If you see no bubbles from the return jets or under the strainer cover after the pump has run a few minutes, your system is running correctly.
 Reply

 Posted: 3/27/2017 

I have NO bubbles going into the pool. The clear lid is tight and full of water with NO bubbles when the pump is running. The problem is when the pump shuts off (either with the timer or manually shut off), there are a few moments and then bubbles appear under the clear lid and then more until the water drains down to a half inch below the top of the basket that is in the container under the clear lid (sorry not good with lingo). When the pump is started, it takes a while to prime but it does prime itself. I'm certain that unless I can find the air leak, this continual priming each time the pump goes on will shorten the life of the pump. Any advice on how to approach this problem would be greatly appreciated.
 Reply

InyoPools Product Specialist  Posted: 3/11/2017 

Rhyno - In reading some of the forums, it sounds like many people have air trouble using a vacuum plate. When you add on the elbow onto the plate, is there a good inch of water above the elbow? Is the end of the elbow able to suck air from the surface? Try attaching a short hose full of water to the end of the elbow and feed it through the skimmer opening before attaching the hose to the elbow. Make sure the end of the hose is well below the surface of the pool. Turn pump on and see if that prevents air from getting into your system. Then attach the rest of your hose to the short hose. If that doesn't solve your problem, try buying parts to replace the vacuum plate with a direct connection to the bottom of the skimmer. See our guide to "How To Operate a Pentair Kreepy Krauly Cleaner Through a Skimmer".
 Reply

 Posted: 3/10/2017 

Hi thanks for the reply ... I get air in returns and pump cavitation even without the hoses and vacuum connected. When I put the plate on top of the skimmer still OK but as soon as I conect the 90 degree attachment onto the plate for the hose to connect to is when the problem arises. I.e when suction line under load .
Thanks again for reply.

 Reply

InyoPools Product Specialist  Posted: 3/6/2017 

Rhyno - Sounds like your air problem is definitely with the suction port and anything attached to it. Part of the suction cleaner hose lies on top of the water. The hose may have developed leaks at the connections. Try submerging the hose below water so that everything from the cleaner to the suction port is under water. If the air bubbles stop, try isolating the leak by removing sections of the hose one at a time.
 Reply

 Posted: 3/4/2017 

Hi I have quite a lot of air entering my pool via both return jets and pump cavitating. I recently installed a new system as the old one was more than 40 yrs old, in fact I replaced everything EXCEPT the suction line !!! However this problem only occurs when I plug the automatic cleaner ( Baracuda ) in . I get absolutely no bubbles when just running skimmer alone. Don't think im losing water. ( just the usual amount as is summer here and 40 degrees c plus most days) Have checked connections and water levels ok and pump is brand new. This was happening only slightly before new pump installed and is now worse. Got me pretty baffled.
Any help appreciated.
Cheers,
Aussie Rhyno.

 Reply

InyoPools Product Specialist  Posted: 2/20/2017 

Wes - If you weren't having bubbles before you changed the filter unit (pump?), I would check the connections around that unit first for air leaks. Then I would check the diverter valve for leaks. Lastly, you could have someone do a pressure test on the suction side of your piping to see if you have an underground leak. Note, if these bubbles only occur in the first few minutes on startup, you have no problem. The system is just clearing air in the system while the pump is priming.
 Reply

 Posted: 2/17/2017 

I have a lot of air bubbles coming from the return jets at the shallow end, but hardly any from the deep end. I just had a new filter unit put in -- the old one was leaking from the lid. I have a Jandy three-way valve, and I notice when the skimmer is shut off and the main drain is left on, the bubbles persist, but when I shut off the main drain and only leave the skimmer on, the bubbles stop. Do you think I would have an underground problem or something easier? The pool's water level doesn't appear to be declining quickly; I don't know if that means anything as far as an underground problem might go. Any advice you could give I'd be grateful for. Thanks! --Wes
 Reply

InyoPools Product Specialist  Posted: 2/13/2017 

Roman - If your pool water is cloudy and your system is operating at 30, you should probably replace your filter. Your cartridge may look clean but after 1 or 2 years of use, the folds of the cartridge may become clogged with oils and chemicals that are difficult to remove. Most systems drain some of the water when the pump is shut off. If you have significant drainage, you may have back pressure building up in the top of your tank. Most cartridge systems have a breather tube down the center of the tank to bleed off any air that collects in the top of the tank. Make sure that tube is not clogged. Also, check for suction leaks in the lines between the pool and the input port of the pump.
 Reply

InyoPools Product Specialist  Posted: 2/13/2017 

WirelessDude - I would replace all the gaskets/O-rings on the suction side of the pump first. They are the easiest to correct. Then check and tighten inlet pump connection if required. Then check the skimmers for leaks where they connect to the supply pipes. If you have low water pressure, make sure the impeller in the pump is not clogged. Slight air leak at the pressure relief value, not an issue. Some people run them this way to relieve any built up air in the tank.
 Reply

 Posted: 2/13/2017 

I have a pool with PCF 150 cartridge filter, salt chlorinator and solar heating. System is 7 years old and has worked fine until recently.
Now filter does not seem to be removing very fine particles and water remains slightly cloudy and pressure gauge doesn't get above 30 psi. When running there are no visible leaks in system. Suction pressure is v. good at skimmer. Once pump stops I can hear the filter gurgling as air enters it and the water drains out somehow. When the pump comes back on I need to open the valve at top of filter to allow air out and it seems like water has completely drained out of filter whist pump is off. I have thoroughly cleaned o-ring on lid of filter and applied small amount of silicon grease.
Would love ideas about what is causing this.
Thanks
Roman


 Reply

 Posted: 2/5/2017 

Recently cleaned and changed filters, skimmer overfilled with debris, so full that with the pump on could not pull it out. Later bubbles started on the jets, small leak on discharge pipe from pump. Have one skimmer with shut off valve, second shut off value for Main Drain and another skimmer. when I turn off main drain valve, bubbles are less but still present.
Both valves open, lots of bubbles, big drain valve closed less bubbles, skimmer valve closed, big drain open slightly less bubbles. What are the chances of two separate lines sucking air into the same pump?
Previously the pump had significant debris, at least the most I have seen because the pot basket broke when the skimmer clogged...
Thinking connections at the pump? valve o rings? gaskets in pump?
Replaced housing gasket on hayward, replaced basket gasket, system is 7 years old and the pressure release on top of tank seems not to be air tight, slight air release.

 Reply

InyoPools Product Specialist  Posted: 2/5/2017 

Very Puzzled - I'm puzzled too. Did the pressure test cover the whole suction side? You might have leaks around the skimmer or the cleaner hoses. A partial blockage would not introduce air into the system and you would need air to cause the air pressure buildup and backpressure after turning the pump off. Look further for air leaks on the suction side.
 Reply

InyoPools Product Specialist  Posted: 2/5/2017 

Blakney - I'm not sure what's going on here. This guide discusses suction air leaks that cause air bubbles in your system. Suction leaks occur before or in the pump. Your filter and multiport valve are after the pump on the pressure side of the pump and any leaks would show as squirts of water. It isn't clear from your description what your problem is. In filter mode, you may be building up air pressure in the top of the tank due to suction leaks. In recirculation mode, you would be bypassing the filter and returning straight back to the pool. This would avoid air pressure build up, but you should still see bubbles coming out of the returns.
 Reply

 Posted: 2/3/2017 

I just had a pressure test done by a leak detector company, held 24 lbs for 10 minutes, was told no leaks. Skimmer side, no problems, vacuum side leaks enough so skimmer lid blows off when pumps goes off. driving all of us crazy. every obvious thing done, defintely only on vacuum side, could a partial blockage appear as an air leak?
 Reply

 Posted: 2/3/2017 

I only seem to have this problem when in filter mode. Its fine if it is in recirculation mode. Any ideas?
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InyoPools Product Specialist  Posted: 1/9/2017 

millbrook AL - Sometimes air pressure will build up in the top of the filter tank which will cause blow back through the pump and skimmer when the pump is turned off. Check that the air relief tube from the top of the tank to the bottom is not clogged. If the leak you have identified is on the input side of the pump, you may have found the air leak that is letting air into the top of the tank.
 Reply

 Posted: 1/9/2017 

I have an in ground pool and had a pool company come out to try and find an air leak. They said the could not find it. At the end of everyday what ever is in the skimmer ends back in the pool and sometimes the skimmer cover blows off. I have a Polaris and found small dripping leak there right before all this started. HELP
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InyoPools Product Specialist  Posted: 12/19/2016 

rbracer - You may have a blockage in your spa to pump line. Have someone snake or blown the line out.
 Reply

 Posted: 12/15/2016 

I have a pool and spa. When I turn the spa on (and close the main drain and skimmer) the water level drops in the basket and the pressure drops about 50%. Water still comes in, but never fills the basket. I cannot find any evidence of a leak around the connections (which are all glued together).
 Reply

InyoPools Product Specialist  Posted: 11/10/2016 

diana - If everything in your pools system seems to be working except the pressure gauge, I would question the new gauge. I know it is improbable, but sometimes you can buy a bad pressure gauge.
 Reply