Why Is Air Getting Into The Sand Filter & Pump?

by Chris
(Utica, NY)

I have a standard Hayward sand filter and Hayward Power Flo Pump. It's an above ground pool. After priming the system and getting the air out, the system seems to be running just fine. When I shut off the power to the pump, a large amount of air comes back up the line into the skimmer, blowing the basket out of its seat.

Once I open the strainer cover to reprime the system and turn on the pump, everything seems to be fine until I shut the pump off again and the same expulsion of air comes back up through the system.

I have replaced the strainer cover o-ring and there doesn't appear to be any cracks in the strainer cover and I'm still having the same problem. There is a very very small water leak coming from the filter pressure gauge.

Any thoughts?

Thanks for the question Chris

We can start with the obvious. Be sure your water level is up 1/3 - 1/2 from the bottom of the skimmer. If equipped, be sure the skimmer weir is moving back and forth properly.

The small leak on the gauge probably wouldn't cause such surge of water. If the gauge doesn't drop to zero when you turn the pump motor off, it's probably bad and needs to be replaced.

If it does drop to zero, but leaks a little, you can unscrew the gauge and replace the O-ring on the end of it. That should work. You can also put a little plumbers tape on the threads. Make the gauge snug, don't over-tighten. Check around the system for any leaks or wet spots. You might be drawing in air that way.

Many pool have what's called a "check valve". This is about the size of a baseball or softball in the line near the filter.

For pool systems, the check valve is used to insure that water flows in only one direction. If your check valve is bad or broken, it needs to be replaced. This may solve your problem.

If all that checks out alright, you may have a suction side leak. You may not have water leaking from the above places.

Here's what you'll want to look for:

*Low water levels

*Skimmer weir stuck (as stated above)

*A broken suction line from the skimmer to the pool pump motor

*Loose pump lid or bad gasket

*Loose fittings in and out of the pump

*Worn our pump seal

Here's a very good post that I recently answered:

How Do I Fix Low Skimmer Suction?

Not all will apply to your situation, but there's alot of good information and troubleshooting on that page. Many parts to check out on your system.

Hope this helps and have a fun and safe swimming season.


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Jan 12, 2015
Why Is The Pool Water Not Being Filtered?
by: Jill

I have a Jacuzzi Laser and it is not taking out the water to be filtered. It is however getting a lot of air into it. Can you suggest why the water is not being filtered. I have tried everything, no blockage, cleaned etc..

Thanks for the question Jill

I have answered very similar questions about loss of suction in these posts:

Why Is Air Getting Into The Sand Filter & Pump?

No Water Flow Through Glass Sight Gauge On My Filter System

How Do I Fix Low Skimmer Suction?

While not all will apply to your situation, the troubleshooting is the same. The last post is one of the best. Look them over and if you still have questions please feel free to contact me. I will merge your question in the post "Why Is Air Getting Into The Sand Filter & Pump?" This can be found on the pool Q&A page in the "Sand Filters" category.

Hope this helps and have a fun and safe swimming season.


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