Air in Filter

by Tim

When we run the filter with water coming from either the skimmer or the center drain, it works fine. The problem comes when we shut the filter off. As soon as it is shut off, large amounts of air bubbles explode through the return.

The sides of the pool vibrate because the pressure from the air is so intense. This has been happening since we hooked the filter up this year. This has never happened in the all the years we've had the pool. What could be causing this? Thank you for your help.

Hi Tim.

It sounds like air is getting into your system while it is running and releases when it is shut off. Since it never happened before I would inspect the connections to the pump. Also inspect the hair and lint pot with the filter running. If you can see air under the lid, there is a leak, either in the pot lid or before the pump.

Sometimes air leaks will drip water when the system is off so closely inspect the system running and not running. Using the filter air relief before shutting it off might help also.

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Air Bubbles in Strainer Pot

by Amy
(Westminster, MD)

I have an above ground pool. When I first turn on the pump, a few small air bubbles appear in the strainer pot. Eventually these bubbles go away but every few minutes, I see tiny - almost microscopic - bubbles moving around in the strainer pot.

Is this okay? Should I do something about it?


Hi Amy.

It doesn't sound like you have a serious problem but you do have a small air leak. The most common place for these air bubbles to come from is the lid to the hair and lint pot. You could try removing it and greasing the o-ring with aqua lube. Most of the time this takes care of the problem. Replacing the o-ring is the next thing you could do.

The fittings on the pump and skimmer should be checked for leaking as well as the hose clamps. The hose from pump to skimmer could also have a very small leak in it. Anything that is drawing air, from the pump to the skimmer, should also leak water when the pump is turned off. With the pump off, look for any signs of water leaking. This could be tiny water drops or possibly calcium deposits from where water has been leaking. It just takes a tiny hole for air to get through when the pump is running.

Another thing to check is the skimmer. With the pump running, look inside and see if there is a funnel in the water that could be drawing air into the system. Something as simple as the flapper not working properly, could cause the skimmer to create a funnel, that would draw air into the system.

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Sand Filter Gurgeling

Why does it sound like my sand filter is always trying to fill with water? But yet the return flow into the pool is good.


It sounds like air getting into the system. Air bubbles in a sand filter will make a gurgling sound.

Air in the system can be caused by not enough water in the skimmer, or something blocking the skimmer causing it to empty faster than it can refill. If the skimmer seems OK I would check the hair and lint pot.

The hair and lint pot is the most common cause of suction side leaks. Most pots anymore have a clear lid so you can see into them. You should not be able to see any air at all. If this is the problem you could try putting aqua lube on the o-ring and see if that seals it. The o-ring could be replaced as the next step. If the lid has a lot of sideways play in it the housing may be warped and need replaced.

Another cause of leaks might be the hose connections on the hose going from skimmer to pump. Most suction side air leaks will drip water when the filter is turned off. That is a pretty easy way of finding the leak.

Air bubbles in the return flow are a good indication of a suction side air leak. The filter will still function normally, with a strong flow in most cases, but you should be able to see air bubbles. If there are no bubbles in the return and no air leaks then there might be a problem in the valve assembly. Rotary valve assemblies use a spider gasket that needs replace occasionally. Water dripping out of the backwash port when the system is in the filter position is a good indicator of a worn spider gasket.

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Pool Filter Questions

by Christine Flanagan
(Oakland, NJ USA)

I just replaced the pump on my Hayward filter because it wasn't cleaning the water properly. I had to vacuum every day. Clear water but always brown spots of sentiment. Cartridge is new . Put it in this year. May 25th pressure was always at 12 to 15 and then it went to 20 , 22. That's when I replaced the pump. Pressure is still at 22, and the first basket in the pump that catches the escaped debris used to not show air, just circulating water. Solid flow. Now there continues to be air. Doesn't fill completely. I also replaced the air release. Don't know what else to do.

Hi Christine
Air bubbles in the hair and lint pot indicate an air leak on the suction side, usually coming from the lid. Make sure you have plenty of Aqua Lube on the o-ring and that the lid is on tight.
Brown stuff in the pool is usually algae, not a filter problem, vinyl shock treatment usually takes care of that.
The pressure ready could just be a bad gauge. If the water going back into the pool is it's usual strong flow you are just fine. An actual reading of 22 would also have a weak flow of water to go with it.

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