9 Reasons Why Your Pool Filter Keeps Filling With Air


photo of air in pool

Having a pool on your property brings many benefits, especially on hot, steamy days. If your pool works correctly, you can have years of fun while keeping cool in your yard. However, a pool requires a lot of upkeep to ensure it is safe to swim in.

The reasons your pool filter keeps filling with air could include a line break, low water levels, filter cracks, or impeller problems. There may also be manufacturing defects, skimmer issues, or loose filter parts. These are only a few of the reasons your filter could be filling with air.

While the presence of air bubbles may not seem like a big deal, it has the potential to lead to many more problems if it doesn’t get immediate attention. In some cases, ignoring air in your filter could lead to explosions and even be deadly. Let’s talk about nine reasons why you could have air in your filter and what you can do to rectify the problem.

1. There’s A Line Break in Your System

A break in the line that connects your pool’s main pump to the skimmer can cause air bubbles. With a leak, your pool won’t have the pressure to move the water from the pool to the filtration system. The system will begin to suck in air instead of water, leading to bubbles being pushed through instead.

A quick assessment of your pressure gauge can help you see if you might have a leak. Always verify that your pressure gauge is working correctly to prevent issues like this from going too far and causing more damage. The next step will be to repair the leak. 

  1. For safety’s sake, turn off your pool pump. Then, fill your pool so that the water level is above the skimmer by at least an inch.
  2. Then you’ll need to remove the lid of your skimmer basket and clean the affected area. Depending on the debris, you may be able to clear it out with something as simple as a philips head screwdriver, some soap, and a scrubbing brush, or even sandpaper.
  3. Next, apply marine putty to the area as directed by the instructions on the putty you use. Epoxy putty is also highly recommended.
  4. Wait the appropriate amount of time for your putty to seal and set. If leaks persist, repeat the steps.

2. You’ve Allowed Air Into the System Via a Filter Change

If you just cleaned or replaced your filter or opened your pump basket for any reason, you’ve allowed air into your filter system. If you don’t release the air, it will move through your filtration system, often increasing the water pressure. 

photo of filter pressure gauge

This can lead to mechanical and physical damage should the pressure build up to the point of explosion. Luckily, it can be easy to eliminate air from your system. Though it can vary widely from pool to pool, generally, these are the steps to follow:

  1. Make sure your pool pump is on and in filter mode if applicable.
  2. Slowly open the air relief valve located somewhere on your pool filter. If you have trouble finding it, see the manufacturing guide for your pump model for details.
  3. As the air leaves your filter, you’ll hear it go with a whistling or a hissing sound. Keep that valve open until water begins to flow out of it.
  4. Close the air relief valve.

If this doesn’t solve the issues that you’re having, it may be time to try another method or contact a pool repair specialist.

3. There Are Manufacturing Defects in Your Filter

You might have a pool filter with a previously undetectable manufacturing defect. These errors happen from time to time, despite quality and safety checks. Even the most well-built and intricate pools can be prone to these issues.

If you think you have a manufacturing defect on your hands, be sure to contact the company that made your pool. Many companies will attempt to right any wrongs made on their end.

4. There Are Clogs in the Skimmer

Your skimmer might be clogged. This part of the filtration system is where water is sucked from the pool to pass through the filter. When air moves through the skimmer along with water, it can lead to a build-up of air in the filter. Luckily, fixing a clog in your skimmer can be reasonably simple.

  1. Turn off your pump completely, with no risk of it turning on. You’ll have a much more dangerous problem if it turns on midway through your work.
  2. Before doing anything else, clean your skimmer box of any gunk or debris.
  3. Run a snake through your intake pipe and remove any debris. You may also use a specialized hose jet that will help better with the angles found within your skimmer.
  4. Secure any removed parts back where you found them, and turn your pump back on.

Related: How To Increase Suction in a Pool Skimmer (6 Ways)

5. You Have Loose Filter Parts

The filter mechanism has several parts that might have become loose, or their seal is no longer airtight. Either way, your pump allows air into the filtration system through these cracks and prevents it from working correctly. 

photo of o-rings

If you can find a specific point where water is leaking from your system, take your time to look at all the connective parts, screws, knuts, and seals. If there’s any obvious damage like cracks, breakage, or rusting, replace them as soon as possible. Tighten up all of your parts, and make sure that everything is sitting correctly and snugly together.

Anecdote: I’ve recently had this exact issue. The o-ring fitted to the drain plug on my pool heater was weathered and caused a terrible leak in my system. Every time my system turned on, all the air would push out of my return lines until the pressure of the system built up.

You might not be able to see if there are any joints or connecting parts with leaks if you aren’t able to find water dripping out. If you can’t find a leak on your own, it’s time to call a professional to help identify and fix the problem.

6. Your Water Level Is Low

When the water level is too low in your pool, it pulls in air that gets to the filter. This can cause many problems in the long run.

photo of skimmer waterline

If this is your issue, add more water to your pool and release air from your filter system if needed. The water should be halfway up your skimmer box. Be sure to monitor your water level, especially during heat waves. It may evaporate quicker than you anticipate.

7. There Are Cracks in Your Filter

Check to see if you have any cracks in your filter system. Cracked lids can happen without any warning and will let air into the filter.

This issue is one where you’ll want to call a professional immediately. Someone experienced in pool maintenance should be able to fix any cracks and also quickly identify the underlying problem that caused the issue in the first place. This way, you shouldn’t have to deal with this issue again, at least for a while.

8. You’re Dealing With Impeller Problems

You might have a broken impeller, which is a component of your filtration system that forces water to move through it. If the flow of water isn’t consistent, you can get air in your filter. 

There are two significant signs to help you diagnose this issue. 

  • First, make sure to check your filter pressure. A symptom of an impaired impeller can be that your pressure is much lower than usual. 
  • Second, be sure to use your ears to help diagnose this problem. People often report a grating or grinding sound from their pool that isn’t the norm.

Be sure to be very careful when it comes to replacing your impeller. It’s a very complex process for a piece of equipment vital to keeping your pool a safe, fun oasis.

9. You’ve Installed the Wrong Filter

It might seem as though replacing a pool filter should be easy, but the wrong filter can cause significant damage to your filter system. If a filter doesn’t fit or the placement is incorrect, you can have a problem with air build-up, increasing the pressure on the unit. Pressure has to be released at some point, and it can be devastating under the right circumstances.

photo of dirty cartridge filter

Every pool model and manufacturer will have a different type of filter. If you’re unsure what kind of filter system you have, check out your manufacturing guide or even give a call to the service that installed your filter for more information. The guide should have specific details on your pump and filter type, and a professional should easily be able to tell you about past work they’ve completed.

Also, ensure you know how to install the right filter for your system. If you’re unsure how to select and install the right filter, you can learn about the wide variety of different types in this video:

And if all else fails, call a pool maintenance professional if you don’t want to take any chances with safety and your pool’s functionality. 

Final Thought

There are many reasons why your filter could fill with air, many of which can be remedied with just a little elbow grease. In any case, this article hopefully provided some useful info for troubleshooting your filter.

Michael Carpenter

Hi, I'm Mike. I grew up in North Carolina having a blast on trampolines, go-karts, and just sitting on the porch with my friends. I have since moved to Las Vegas with my wife, 2 children, and 3 dogs. When I'm not chasing the kids around the house, I am probably chasing them around the backyard!

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