How to Identify and Correct Air Leaks

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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.

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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 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.

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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 start to gulp air with the ebb and flow of circulating water.

This simple problem has a simple fix: add water. Drop in a hose, and get that water level up. Keep an eye on it in the future to prevent a reoccurrence. A simple add-on feature is water levelers, that make sure your water is always at optimal levels.

Step 3

Before we begin the actual inspection of 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. The air relief is generally only found on Cartridge and De filters. Sand filters do not have this feature, so expect some splashing when accessing plumbing elements like the pump strainer lid, and unions.

Step 4

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

Check the rubber gasket for cracks pinching the gasket 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 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, this allows for 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

PVC plumbing glued joints like tees, elbows, and valve ports are another common culprit. The epoxy sealing these joints can become brittle and washout overtime. This can create a progressively worse and worse air leak leading to complete pump priming failure.

The smoke, soapy water, or shaving cream method is the standard way of finding these leaks. 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 maybe pinhole-sized leaks in one or multiple hose sections. To find and replace these hose section:
  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
  4. Complete this for each hose section, replace the sections with holes
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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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(1 to 40 of 604)

 Posted: 6/27/2022 

First, let me say thanks. This is perhaps the most useful site I've found for newbies. Here's our issue: Finally had an opportunity to open the pool this season this past week. New pump installed. So, we did all the chemical stuff and started her up. Worked like a champ. Great pressure from the jets -- we think the best we've ever had -- and a full to the top of the glass pump...went to bed and woke up and the pump's water level was down maybe two inches. Jets were still working, but not as robustly. So, we backwashed just because -- no other reason other than we remember last year that backwashing always brought the water level in the pump back to it very top. Same scenario: Running like a champ, great power out of the jets, pool well along in the cleaning process, the pump was filled 100 percent when we went to bed. This time woke up to a pump that had lost maybe only an inch of water. By the way, all the other things were fine: Weir working fine, skimmer basket clear, water level steady just above the midway point arrow. Thoughts?
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InyoPools Product Specialist  Posted: 6/30/2022 

When the pump is turned off, does it lose prime? If it does, there could be an air leak; but you didn't mention if air bubbles were flowing from the return. Do you have a sand filter? If so, how old is the sand? Filter sand usually lasts 3-5 years before it requires changing. Eventually, the sand will get so dirty that backwashing will only solve flow rate issues for as little as a few minutes before the pressure begins to spike and the flow rate dips. And if you are losing 2 inches of water in a night, are you seeing any water pouring from the valve's waste line when it is set for normal filtering?
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 Posted: 6/23/2022 

I have air bubbles coming from a return (deep end is more visible than at the stairs) when pump is set to skimmer. When it’s set to drain there are no bubbles. I replaced the o-ring at the union for the return from the skimmer. Are the cemented connections next? Also, what product is best to seal from the outdide?
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InyoPools Product Specialist  Posted: 6/27/2022 

Is the water level at least halfway up the skimmer's face? If the water is just a tad too low, the skimmer can gulp air with the ebb and flow of water through the weir. If you haven't found the leak, you'll need to run through all the plumbing elements; the glued PVC joints would be an excellent choice to check next.
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 Posted: 6/27/2022 

Thank you. There’s plenty of water so I’ll check those connections. I’m surprised water doesn’t leak out of a connector but that might be a matter of physics.
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InyoPools Product Specialist  Posted: 6/29/2022 

Okie Doke. If you find a resolution to your problem, please give us an update.
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 Posted: 6/20/2022 

Hi… We have a combination of two problems and I think they may be related. Anyway We lose significant levels of water [2 to 3 inches a day] up until just below the skimmer intake where the leak stops… therefore in my mind eliminating the chance this is a leak from the liner. Along with this we noticed significant amount of bubbles in the pool return. I therefore assume there must be a break on the suction side of the system [allowing the air to come in and cause the bubbles and water to escape to cause the leak] Debating if I need an ultrasound to find a source of a leak or if a pressure test is enough. Also can I conclude that the leak is in the plumbing above ground ( skimmers and initial part of plumbing) given the significant bubbling?
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InyoPools Product Specialist  Posted: 6/27/2022 

If the water level stops at the same level every time, X marks the spot. It sounds like a leak in the liner, skimmer face plate, or housing has been compromised. The air leak is likely above ground; the water leak is either in the pool basin or the underground plumbing; if you can't see an obvious leak above ground. Follow the steps in this guide to find the air leak. For the water leak, the following guides can be used: Swimming Pool Leak Detection TipsMy Pool Is Only Losing Water When My Pump Is Running
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 Posted: 6/20/2022 

Hi! I have a sand filter. My pool pump likely started sucking in air bc the water got too low. Filled the pool up and started up pump. Still have air bubbles from returns and sounds like there’s air inside the filter. When I turn it off the water sends back down the piping to almost empty my pool pump.
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InyoPools Product Specialist  Posted: 6/30/2022 

Does your filter have an air relief valve on top of the tank?
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 Posted: 5/2/2022 

Hi. I have air bubbles coming from around the returning water into my in ground salt water pool. My pool guy seems clueless. He “thinks” could be this. Could be that. Could be my heater??! Really? Don’t think so.. I see some bubbles thru the suction lid so it’s getting air someplace somehow! I’m concerned for the filter burning out. He says oh no that can’t happen? Really?
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InyoPools Product Specialist  Posted: 5/11/2022 

It sounds like the only way to find out is to do the troubleshooting yourself. Follow the steps, go through the elimination process, checking off things it's not so you can narrow it down to what it could be.
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 Posted: 4/20/2022 

I have air coming from the return, it's a wc112-147 valve on a t-240bp-1 sand filter. No air in the pump strainer so unless it's the pump it seems to be the valve. When I turn off the pump the strainer starts filling with air and I hear air around the valve. Should I just replace the whole valve? Thanks.
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InyoPools Product Specialist  Posted: 4/21/2022 

I don't believe the air leak is coming from the filter valve. The filter and the valve are on the pressure side of the pump. If there is a hole there, water would be leaking out, not air going in. We mention quite a few things to check in the guide; I'd go through them before replacing a valve that's not the cause. Do you have a salt system? If so, does the air bubble problem only happen when it is on? The air bubbles could be a byproduct of the cell's normal operation; it wouldn't be a cause for concern.
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 Posted: 1/24/2022 

I have an in-ground pool, a brand new pentair cartridge filter with a pentair VS pump. I recently had an issue where both of my skimmer baskets floated due to an over abundance of pear tree leaves where my line was fully clogged (For the record - I hate pear trees!). I managed to unclog the line to where water is flowing again, but every time I turn the pump off water rushes out of the pump and the line loses pressure, causing me to have to prime the pump every time before I turn it on. If I don’t do this it will run dry. I have checked for air leaks in the lines above ground and am not finding anything. I also replaced my old check valve for good measure. Both skimmers are also sucking in water just fine, but I am getting a massive amount of bubbles in only one of my return jets, which is the one closest to the pump. All other jets are operating and moving water just fine. I also have a lot of air suddenly in my pool sweeper line. I’m thinking I either have an air leak underground or a clog somewhere in the line. I question if it’s an underground leak though as I didn’t have this issue until the leaves clogged the line. Is there anything I’m not thinking of or a way to further troubleshoot/blow out the line should it be a clog or anything else I am not thinking of?
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InyoPools Product Specialist  Posted: 1/25/2022 

An air leak caused by an underground pipe is possible but a rare occurrence. Therefore, I would put that possibility on the backburner for now.What have you done with the pump since the peach tree issues? Have you changed or inspected the pump lid gasket? if the gasket was pinched or knocked out of line while you were servicing the clogged plumbing or priming, it could cause an air leak. The air leak might not be big enough to prevent it from priming completely. But the leak could be big enough to cause a water purge once the pump shuts off. Another option, test the leak after you shut off the pump instead of when the pump is running. So, you would prime the pump, let it run, stage your bubbles or smoke implement, then turn off the pump. If the air leak is strong enough to purge your system, it should make a noticeable divot in the foam or pull in the smoke.
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 Posted: 8/29/2021 

I only have bubbles upon starting up the pump. I get a large burst of bubbles out of one jet only, once that's done there are no more bubbles. Not sure whats happening?
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Anonymous  Posted: 4/25/2022 

Wouldn't an underground leak pull some muddy water into th system?
 Reply

InyoPools Product Specialist  Posted: 4/26/2022 

The water pressure would prevent the mud from leaking into the pipe. If any dirt seeps into the system, the filter will prevent most of it from returning to the pool.
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InyoPools Product Specialist  Posted: 9/1/2021 

You are essentially describing an air leak or, at the very least, an issue with priming. Have you done any of the troubleshooting mentioned in the guide?Unfortunately, I can't tell you what is exactly wrong with the system based on the description. But the troubleshooting and list of things to check should narrow the field of possibilities or pinpoint the issue.
 Reply

Anonymous  Posted: 8/6/2021 

I narrowed the air leak to to one strainer , water level is good when i shut down that valve bubbles go away could it be small debris in the line ?
 Reply

InyoPools Product Specialist  Posted: 8/6/2021 

Which strainer is it? Is this a pump or skimmer strainer? Debris does not cause an air leak; it would cause a pressure drop, however. If air bubbles stop after closing a specific valve, I would start by investigating the valve first, then working your way back to the pool, checking any seams and joints for cracks.
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Anonymous  Posted: 7/19/2021 

I have a pool that is less than a year old. When the pool was brand new we set the pump to around 2,300 rep and the return water filter and jets had good pressure. However recently I have noticed that at 2,300 the return output has decreased substantially such that instead of a decent waterfall it turns into a trickle. The PSI is around 10 to 12 PSI so not that high but higher than when the pool was new. Also when the pump turns on , it operates normally with a decent return and over time it degrades to a trickle? What could the problem be? I have checks the leaf basket as well as the basket in the pump. no issue there.
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InyoPools Product Specialist  Posted: 7/20/2021 

This doesn't sound like an air leak problem. You either need to clean your filter, your baskets, or the impeller if it is clogged. More info - How to Correct Low Water Pressure in Your Pool System
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 Posted: 5/22/2021 

I have air bubbles coming from two of the return jets whenever my variable speed pump is set to less than 67%. None when its higher. When its at 55% and lower it gets more and more air the lower I set the pump rate. Does this mean there is still an air leak? Or is this a normal side effect of setting pump rate low??
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InyoPools Product Specialist  Posted: 6/4/2021 

At the lower speeds, there may be air bubbles that exit the jets. Do you happen to use a salt chlorine generator on your system?
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 Posted: 5/22/2021 

I tried for hours chasing down what i thought was a suction side leak, tore apart valves, pump inlet and cover, it would work fine for like 2 minutes and then the bubbles would return... strange thing was it got better at higher pump speeds... it finally clicked for me and I remembered that my salt water chlorine generator creates chlorine and hydrogen in gas form and that was the bubbles I was seeing! turned off the chlorine generator and wouldn't you know about 30 seconds later I had zero bubbles!
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 Posted: 8/5/2021 

Had same issue! Turned off salt cell and boom! Bubbles gone
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InyoPools Product Specialist  Posted: 8/6/2021 

Awesome!
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Anonymous  Posted: 7/30/2021 

Oh my gosh! Just tried turning off my salt water generator to see if the bubbles stopped and success!! Thank you so much for posting this!
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InyoPools Product Specialist  Posted: 8/3/2021 

I love when one flick of a switch gives you a little peace of mind. 
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 Posted: 7/24/2021 

Thank you. You saved me a lot of time.
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InyoPools Product Specialist  Posted: 6/4/2021 

Oh jeez, that is relieving and frustrating all at the same time. Good job, ferreting out the problem.
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 Posted: 1/31/2022 

Thanks so much for this tip. I turned off my salt generator and the bubbles disappeared soon after that. I would have never thought of that so thanks for this brilliant tip.
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InyoPools Product Specialist  Posted: 2/1/2022 

Awesome! And, thank you for reading.
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 Posted: 5/20/2021 

I keep getting high pressure on the filter/low flow return, the de cartridges look ok every time I open up the tank and they are only a year old. When I run the pool on RECIRCULATION the pool flow does not slow down, if I had air leak on suction side, wouldn't the flow also get worse while on RECIRC., or is this due to the air being trapped in the tank only ?
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InyoPools Product Specialist  Posted: 5/21/2021 

 This is not an air leak you are describing; you have dirty grids or charge the grids with too much DE causing a blockage. If there was trapped air in the tank, you would have been able to release it by opening the air relief valve.
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Anonymous  Posted: 5/24/2021 

How do you clear the grids if there is too much DE powder?
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InyoPools Product Specialist  Posted: 6/4/2021 

The filter should be backwashed to clear the grids of DE powder. For an example, look at this guide, How To Backwash a Hayward DE Filter.
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 Posted: 3/8/2021 

We have an in-ground Chlorine pool (8’ x 25’). For the past five plus years we have run the pump/filter system from 8:00 AM to 4:00 PM daily, and from 2:00 AM to 4:00 AM we run the system with the Polaris vacuum. Last Wednesday morning around 3:30 AM, I woke up and heard a strange noise. I looked outside and the pool was half full. I went outside, turned off the pumps, and noticed the drain plug on the filter assembly had blown out, obviously lowering the pool water level. The preceding Saturday I had cleaned the filter cartridges. Cartridges were purchased in May 2020. I clean them every three months. Air was bled out after cleaning. Normal System pressure: 20 PSI After investigation, the threads were stripped, on the filter assembly, where the drain plug fits. On Saturday, I replaced the bottom portion of the filter assembly and also installed a new gasket between the top and bottom of the assembly. I ran the system, with the Polaris, for about four hours on Saturday, and ran the pump/filter system all night through Sunday at 4:00 PM, with no obvious problems. During the time the Polaris was running, I noticed it was much slower than normal and the Polaris pump was leaking quite a bit. This morning (Monday), around 3:30 AM, my wife woke up to hear an unusual noise again. Once again, the pool level was down, below the skimmer. I ran outside and it appears the gasket between the top and bottom filter assembly failed, as water was spraying out. It appears that something is over pressurizing the system, causing two failures within four days of each other (drain plug and gasket). I have no idea what it could be. Does it have something to do with the Polaris, or is the leaky Polaris the result of the higher system pressure? Looking for ideas on areas to investigate. Thank you.
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