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Common Causes of Air in Your Pool’s Pump & Filter System

Published by E-Z Test Pool Supplies on 05/15/2017

Common Causes of Air in Your Pool’s Pump & Filter System

Excess air in your pool’s pump and filter is the symptom of a problem – one that could be a minor or major fix. Left unaddressed it will cause other problems as well, and those problems could have a minor or major impact. Remember that any pool’s filtration system, even when functioning correctly, will kick out a few bubbles here and there from the return jet, especially during initial start-up of the pump and shortly after. If this occurs at start-up but quickly vanishes after a minute, you need not be concerned. What is more problematic is when large amounts of air, in the form of bubbles, continually stream out of the return(s), and the water level barely fills the trap of the pump while running. Bubbles passing through the return may result in poor filtration, which means cloudy water or algae eventually. Low water levels in the pump trap may result in an overheated or burnt-out electric motor. The first problem (bubbles in return stream) is a pain, but the second is a disaster for your pool, expensive, and may cause issues that will require the attention of a pool professional.

The pump has one job – that is to pull the water (in the case of an in-ground pool) and push it through the filter, lines and any other equipment back into the pool. Without the pump almost all of the other equipment for the pool is useless! And if that pump cannot pump water but continues running pushing air, it will overheat and burn out in a very short period of time. This is why it is very important to make sure that you do not have air in your system, and if you do to remedy it soon before it becomes a big problem!

What Are The Signs of Excess Air in the Pool's Filter System And How To Fix It: 

Let’s start off with something so obvious that it could actually be easily overlooked. That is a water level that is so low that the skimmer(s) start gulping air in with the water. In general, the water should be between ½ and ¾ up the skimmer opening(s) so as not to take in any air at all from the pool! It happens more often than you would expect, actually. Easy fix – raise the water level!

Next, if your filter has a bleeder valve (usually at the top of the filter) open this while the filter and pump are running until water spits out of the valve and then close immediately. This keeps air out of the tank and allows for maximum efficiency of filtration. Keep in mind that a filter tank that is half empty (or half full of air) is only able to do half the job filtering your pool.

Still having issues? Now look for compromises in the pump lid and area right around this. Anything from a cracked lid to a split or overstretched o-ring could be causing air to enter here, especially since suction is strongest right there at this point. If either of these things is true, replace the o-ring or lid. You may see your problem vanish. And remember that it’s best to replace these parts rather than attempting to fix the situation with epoxy or other such band-aids.

Then, if there is no issue there, inspect to see if there is any movement to the plumbing that enters the pump. A small amount of movement in the fitting at the pump could be bringing in tons of air at this spot. If this is the case, tighten or replace this fitting. If this is something you’re not confident in tackling yourself then hire a pool service professional. You may see it as expensive, but try to think of the money you’ll save from having to replace a burnt-out pump motor compared to what it’ll cost to tighten a fitting! We have a  large selection of pool pump parts if you need to replace something.

And if you still haven’t found the source of the leak, then look at the skimmer itself for cracks. As pools age they will settle, no differently than your house may settle, and the movement of all that weight may produce cracks in the skimmer. This may be found using pool leak detection dye (pre-loaded in small syringes) which is slowly squirted into the skimmer while the pump is turned off. If there is a sizeable enough leak here you’ll see the dye leave the wall of the skimmer through cracks in it. If this is the case, then you will either need to patch the cracks with a quality epoxy that works underwater, or replace the skimmer completely. The latter job is far more involved, expensive and usually requires ripping up the concrete deck to remove the skimmer. Either way, do not ignore this, if it is the source of your problem as it will only make things worse on down the line. We have a  large selection of skimmers and skimmer parts if you need to replace something.

The last and most serious issue that could be occurring is air entering through cracked lines between the skimmer and the pump. This can only truly be checked by means of a pressurization test to see if the line holds air pressure and should be checked by a professional pool service company. If you have checked all of the things above, then perhaps it is time to call in professionals to diagnose and possibly repair the problem.

If you have any more questions, we would be happy to help! Visit us in-store or online at