Pool Sand Filter Gurgling: 6 Unusual Defects To Look For!

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Why Is Your Pool Sand Filter Gurgling?

Do you have the problem of your pool sand filter gurgling of late? You are not alone. There are times when you may start hearing a gurgling sound from your pool filter, your pool pump, pool skimmer or some other part of the pool plumbing.

The problem of your pool sand filter gurgling is because of an air leak. Gurgling is the sound of air trying to get past water. Find the air leak & fix it!

In this post I look at different points from where air can get into the pool plumbing. So when you hear your pool sand filter gurgling, you have to check all those potential points for an air leak, one by one, till you find the leak.

The Pool Filtration System

The complete pool filtration system is conceptually the same as the circulatory system of your body. The pool pump is the heart (also a pump) and the pool filter is the kidney (also a filter).

The pool filtration system has a “suction-side” and a “pressure-side” portion. The “suction-side” starts from the pool skimmer and ends at the pump impeller. The “pressure-side” begins from the pump impeller and ends at the return jet.

Air leaks always happen on the “suction-side”, never on the “pressure-side”.

A leak on the “pressure-side” will squirt out water, not suck in air.

What Happens If Pool Water Level Is Too Low?

If your pool sand filter is making gurgling noises then it is possible that the water level in the pool is low. Low water level in the pool can cause the skimmer to suck in air along with the water.

The air travels all the way to the pump and can even get pushed all the way to the pool filter. You may hear a gurgling sound in the pool pump, pool filter or both.

Consider the gurgling sound as an advance warning. If the water level is too low the skimmer can bottom out and the pool pump can run dry. Should that happen you run the risk of the pump motor burn out.

Consider installing an automatic pool level sensor, such as, Fill-O-Matic Premium Automatic Pool Water Leveler. You will never lose sleep worrying about the pool water level.

Skimmer Blockage

It is possible that the skimmer is sucking in air even when the pool water level is correct. This could happen due to a blockage in the skimmer or if the skimmer weir (flap) is broken and stuck.

So, if the pool water level is OK, check out the skimmer. The water level in the skimmer should ideally be ½ to ⅔ way up.

Check Pump Lid & O-ring

An air leak from the pump lid is quite common. This is because the O-ring can dry out and get brittle. Or it may have just got damaged.

It is a good idea to check the condition of the O-ring. If it is physically damaged then you should replace it. If it looks OK but just dry, then lube it up with Magic Lube.

How to Find Air Leaks in Suction-side Valves & Joints?

The valves on the suction side also have O-rings. You could have air leaking in through those or any other plumbing joints. It can be difficult to find the air leak with so many possible points.

Fortunately, there are a few tricks that can help make the job easier.

1. Smoke: Light an incense stick and move it around the joints. The smoke will be drawn in if there is a leak. (Spoiler Alert: Does not work on a windy day!)
2. Shaving Cream: Smear it around the joints. The cream will dimple at the point of air leak.
3. Soap Water: Mix soap with water to create bubbles and smear it around the joints. The bubbles will get sucked in if there is an air leak.

Can Clogging Result in Sand Filter Gurgling?

Sometimes, though it is not common, a clogged pool filter can result in gurgling. It is unlikely that air will get into a pool filter from a source other than the pump. After all, the filter is on the “pressure-side” of the pool pump!

However, if any air is leaking in from the “supply-side”, it will reach the pool filter. If the filter has been backwashed then it should not be clogged. A clean sand filter will function normally and the air will find its way to the return jet. You might notice air bubbles at that end though!

But if the filter is really clogged up, then the air has no place to go. It accumulates in the space above the sand media, along with the water. This is the cause for pool filter gurgling.

You can release the air, using the air release valve on the top of the filter. That is a temporary solution. 

You still have to unclog the filter and fix that air leak!

Underground Plumbing Leakage

OK, this is really unlikely, as the PVC plumbing is pretty tough. PVC of course does not corrode. PVC pipes can also handle the stress that heaving concrete or sinking earth may put on it.

If you have not found anything so far, you could check out the “suction-side” underground plumbing. But, to be honest, that should be the last thing on your list.

Pool Sand Filter Gurgling Checklist

Recommended Pool Sand Filter

Best Sand Filter

The Hayward Pro Series Sand Filter for in-ground swimming pools will provide you with hassle-free, effective filtration. The weather-proof tank is constructed of a tough, color-fast polymeric material.

Even water distribution over every square inch of sand is ensured by an integral top diffuser, self-cleaning under drain and 360 degree slotted laterals. Advanced full-flow technology reduces energy costs by achieving excellent filtration, so you can run your filter less.

Thorough backwashing allows for crystal-clear water. Filter is complete with tank, 7-way multi-port valve, sight glass and pressure gauge. 7-way Valve Positions: Filter, Waste, Winter, Closed, Backwash, Recirculation, Rinse.

Hayward Pro Series Pool Sand Filter

Thank you very much for reading the post. I do hope you found it informative and helpful.