Pool Strainer Overflows..Lid Blows Off..

What To Do When The Pool Strainer Overflows & The Lid Blows Off

I purchased a home that happened to have an above ground pool. Since I know nothing, I had a pool company out last year to get it going. New pump installed and chemicals.

This season, every time I get the water level above the skimmer, the strainer basket behind the pump fills, and whether the pump is on or not, the strainer top blows off (under huge pressure)and the water runs out.

If I leave the top off the strainer, water will overflow until the water level is below the skimmer.

No matter what, I cannot keep the top on the strainer due to pressure.

Can you help?

Thanks for the question

It sounds like your pool has an air leak somewhere. The strainer basket lid would be the most common. Check the gasket around the lid and replace if it's worn or broken.

The air in the chamber is compressible. When the pump shuts off, the air expands and forces water back through the plumbing.

It could also be low water level or a sticking weir. You always want to keep the water level between 1/3 - 1/2 up the skimmer. A too low to too high water level and the skimmer can't do it's job.

A common cause is the weir in front of the skimmer sticks. This creates a vortex in the skimmer which allows air into the suction side of the pump.

You can open the air bleeder valve on top of the filter until water starts dribbling out. That will eliminate the air inside the filter.

Many pools have an inline check valve on the suction side of the pump. This is to prevent backflow to the pool and keeps the system primed.

If the valve is bad you could have reverse water flow back to the pump which would cause the filter basket to pop out and throw the lid off.

Check all of the fittings, gaskets, and O-rings. You can also turn the system off. If you lose any water you're sure to have a leak somewhere.

Hope this helps and let me know how this turns out for you

Best of luck


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Pool Water Back Pressure
by: Robert

Thanks for the question Al

I've answered a similar question that can be found here:

Pool Strainer Overflows..Lid Blows Off..

I've also made videos that detail what to look for on the suction and return side:



The titles are not named what your issue is but the troubleshooting is the same.

One last thing. Some pools have an inline check valve on the suction side. This is to prevent backflow to the pool and keep the system primed. When this valve fails you can see reverse wate flow to the filter basket causing the lid to be blown off.

In order to check the backflow valve you will need to take apart the intake side of the pump suction line. with a ShopVac or something similar, try blowing air through it. If you can the valve is bad and needs to be replaced.

If you feel your situation is more complex than this, I do phone consultations for a donation of your choice. It makes things go much faster and many people have found it extremely beneficial, saving them time and money in the long run. All your questions will be answered. I have nothing to sell you so you know I'm not bias.

Pool Consultation

Hope this helps and have a great Summer.


Excessive Water Back Pressure in Pool Pump with Sand Filter
by: Al Barrs

My pool pump builds up excessive water back pressure while running that blew off (burst) the flexible inlet and outlet water hoses. I repaired and replaces the hoses and today was running the system and when I turned the power off on the pump, water blew backwards and out of the debris scupper basket about 3 feet high in the air; with Jacuzzi Model 240 Sand Filter Multi Port Control Valve.

While running all day everything seemed fine and working as normal. It back-washes and rinses fine. Do I need to remove the sand in the filter and inspect the plumbing inside and replace the sand? Its an Advantage Pool Pump Whisperflow Waterway® Center 1.5hp Pump Model: PBCH15, and a Jacuzzi Splash Model K, MFM Series sand filter system; with a Jacuzzi Model 240 Sand Filter Multi-Port Control Valve.

Thanks, Al Barrs

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