Why Does Air Pressure Build Up Inside My Sand Filter?

by Lynn

My sand filter is old, it used to work fine. It has the plunger on the side of the filter houseing, with 3 lines straight below the handle inline, intake,return, and backwash.

Ok, but now so much air builds up in the filter,that if I don't leave the air valve open, it doesn't filter.

I attached a hose to the relief valve so the water goes back into the pool, but now it has started to blow debrie & Sand up through the valve.

I put a sock over the end of the tube, by the next day the sock had cought about a quart or more of sand.

Can you help me ?

Also, how do you know when to put more sand into the filter?



Thanks for the question Lynn

I'd first direct your attention to similar posts:

High Pressure Problem On A Swimming Pool Sand Filter

Why Is Air Getting Into The Sand Filter & Pump?

Is the gauge working? An easy way to find out is first turn the pump off. If the needle goes to zero, it's good. If the needle sticks, replace the gauge.

If air is getting in through the gauge, you can unscrew the gauge and see if there's an O-ring on the end. Replace it and put some plumbers tape on the threads.

Make the gauge snug, don't over-tighten.

Let's say the gauge is working. Is there air in the pump pot? Try replacing the gasket around the lid and be sure it's only correctly.

You did that. Then there's a possibility that air is getting into the system somehow. 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.

Check around the system for any leaks or wet spots. You might be drawing in air that way.

For some 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.

It's about the size of a baseball/tennis ball on your plumbing.

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

A good post, somewhat long, but lots of good info.

How Do I Fix Low Skimmer Suction?

If you're losing sand, you may have a broken lateral.

Replaced Lateral But Still Sand In Pool

When Do You Know It's Time To Replace The Sand In The Filters?

Sand In Pool After Changing The Filter

Sand normally lasts about 5 - 10 years with good maintenance. During back washing and normal use, you're going to lose a bit of sand.

The best way to know if you need more sand (top it off) is to measure it. This is known as "freeboard" and is the top of the sand to the top of the filter.

You can call the manufacturer of your sand filter to get that measurement.

The links above have other links in them so be sure to look them over as well.

Hope this helps and have a great Summer.


Click here to post comments

Return to Sand Filter Problems.

Pressure Keeps Jumping Up

by Amber

Recently changed out the sand. The filter ran fine before we did this, now it has to be backwashed every 20 min to stay at 20 psi.

Recently added some chemicals to it that said do not backwash.

What could cause my issue with the filter?

Thanks for the question Amber

I have answered this question before. You can find the useful links below.

High Pressure Problem On A Swimming Pool Sand Filter

Sand Filter - High Pressure

Why Does Air Pressure Build Up Inside My Sand Filter?

Due to the similarities in the questions I will be merging your question with the link above entitled "Why Does Air Pressure Build Up Inside My Sand Filter?"

If you need immediate assistance (within 24 hrs) or for emergency personal assistance, you can make a donation of $35 per hour and I'll answer your questions by phone.

If you've found this site helpful please consider making a donation. Thank you.

Hope this helps and have a great Summer.


Click here to read or post comments

Return to Sand Filter Problems.

eBooks Are Perfect Desktop & Mobile Device!!

swimming pool care, basic pool care, above ground pool maintenance, inground, salt water

Click Here To Learn How This eBook Can Save You TONS Of Time & Money

Click Here To Learn The Best Way To Clear Up Your Pool 

All Resources In One Convenient Package. Click HERE To Get Started.

Recent Articles

  1. Pool Float & Sweep

    How do I keep the hose from my pool sweep and the floater from colliding? If I tie the float off where is the best place, and one last if the float is tied off.

    Read More

  2. The calcium hydochlorite will not dissolve in our pool

    The calcium hydochlorite will not dissolve in our pool. It is suspended in the water

    Read More

  3. Easy Swimming Pool Care: Maintenance, Instructions, Tips, Guide

    Simple Swimming Pool Care Guide & Pool Water Chemistry

    Read More