Why Do I Have Air Bubbles in Pool Jets?

Air bubbles coming out of your pool jets and into your pool is a common problem that you may experience, especially when opening for the pool season. If you have just the odd bubble then that can be quite normal but if you have persistent air bubbles, particularly if the air comes out in substantial amounts, then you may have a problem.

The most common reason why you might get bubbles from your pool jets is air leaks caused by a missing, faulty or badly fitting o-ring in either the pump strainer lid or a union on the suction side of your pool system. The other most common reason is a low water level in the pool.

If you have air bubbles flowing into the pool from your return jets then this article will hopefully give you a good idea of what causes it and how to fix it.

Causes of air bubbles coming out of pool jets

You need to understand why or how your pool pump works in order to understand exactly why you’re getting small bubbles coming from pool return.

Firstly, take a look at the pool pump. You will probably see two pipes going into the front of the pool pump. So all the water that’s coming from the pool, either from the skimmers or the bottom drain, is coming through those two pipes and then into the front of the pump. The water is being pulled up (sucked) to the pump from those two pipes. This is called the suction side of the pool plumbing.

The water that comes out of the top of the pump that then returns to the pool, probably via your filter, is known as the discharge, return or pressure side of the plumbing. It is very rare for air to enter the system on the pressure side. If there was a leak anywhere then water is likely to come out, rather than air going in.

Is air getting into the suction or the discharge side?

To narrow down whether it is the suction side (before the pump) or discharge side (after the pump) that may be letting in the air is generally quite easy.

Firstly, take a look at the pump strainer basket housing which will be located immediately before that actual pump. It will have a see-through lid which enables you to see if there is any debris in the strainer basket that needs to be removed without actually taking the lid off.

Can you see any air in the strainer pot below the lid (which will obviously be at the top)?

If you can see so some air in there then the cause of air bubbles in the pool is almost certainly that there is air being sucked into the line on the suction side of the pump. This means you can be quite sure that it’s not anything on this discharge side of the plumbing that is allowing air into the system.

Troubleshooting air bubbles in pool pump

Once you have eliminated the discharge side then you must have a pool pump air leak so the air has to be coming from this suction side. You need to investigate further.

There are three main reasons why air may be being pulled into the suction line of your pool which ends up with your pool jets blowing bubbles of air out. Finding which will indicate how to fix air bubbles in pool return.

1. Incorrect water level in pool

The first thing you need to check is in the pool itself. Take a look at the water level. If the water level in the pool is too low then your skimmer will probably suck in air. This air will travel all the way through the system and end up back in the pool as air bubbles.

Take a look at the pool skimmer entrance. The water level should be halfway up the entrance or a little higher.

If the water level is correct then you should continue with the troubleshooting below.

If it is below the correct level, particularly if it is significantly lower, then top up your pool with a hose. Once it is at the correct level, give the system a while to purge any air trapped in the pump or other components and then check again to see if air bubbles are still coming from the pool jets or there is still air trapped in the pool pump strainer.

If not, then your work is done. If there is still air then you need to investigate further.

2. Pool pump leaking from strainer lid

It is not uncommon for air to be drawn in through the lid of the pool pump strainer (where the pump basket is housed). There are a few things to check to see if that is the cause of the air getting into the system:

• You need to check that the strainer lid is on firmly or that it is not cross threaded. If it’s not on tight then it can suck air in through the lid and obviously should it be cross threaded then it will definitely not make a good seal.
• Turn off the pump, unscrew the pump lid and turn it over.
  • First of all make sure there is an o-ring fitted (located in the underside of the lid).
  • If the o-ring is there, make sure it is in good condition, without any cracks or breaks in it. Replace it if it is cracked, broken or stretched.
  • Make sure it is seated correctly and that there is no dirt or debris caught underneath it which may be preventing it from making a god seal.

3. Leaking union

The most common cause of air getting into the suction side of the system is the union between the pool pump inlet and the pipework that comes from the valve or valves that control the flow of water from the skimmers and the main drain.

The union consists of a threaded connector with an o-ring inside to provide a watertight seal. This is where you would disconnect if you needed to replace your pump.

With the pump still off (of course) unscrew the connector. You may need a large wrench to get some extra leverage if it has been connected for some time.

Once it is unscrewed, slide it away from the pump and take a look inside. Check that the o-ring is there. If it is then check that it is seated correctly in the groove just inside and that it has no defects or debris under it which may be letting air in. Replace it if it is cracked, broken or stretched.

Quite often the problem is that the o-ring is loose in the union. When the union is put together it is easy for the o-ing to be dislodged from the groove so it is completely or partially free. If that is the case it will not make a good seal and air will get in.

With the o-ring seated correctly, make sure that the pump and the pipe are properly aligned and then gently tighten the connector. Once it is tight then there should be no gap between the flange on the pump and the connector. If there is a gap that probably means that something is obstructing the union from fully closing. It may well be that the o-ring has become unseated, so repeat the process until the union closes properly.

4. Pump drain plug

Although this would be unusual, most pool pumps have a small drain plug and it is possible that this isn’t sealed properly allowing it to leak air into the system.

Testing the system

Now you need to find out if anything you have done above has solved the problem.

Turn the pump back on and then let it run for 5 minutes to prime and get rid of any air that will be in the system when you opened the strainer lid and the union. If you have had your pool for some time you will have an idea how long it normally takes for all of the air to clear out, so if that is longer than 5 minutes then allow for that.

Once it has had a chance to prime can you see any air through the strainer lid now? If you can see there are a few small air bubbles in there that is actually quite normal, particularly at startup, and they will probably disappear in time.

Now go over to the pool and take a look at the return jets. Hopefully, there are now no air bubbles in the pool jets and only water is being pushed out of them. If that is the case then your work is done!

Still have air bubbles in the pool jets?

If you have tried the solutions above but you still have air bubbles in your pool jets then it may be one of the following:

Air leak in solar panels

If you have solar panels that heat up your pool water then this could potentially be the cause.

Although the solar panels will be on the discharge side of your pool system it is possible for air to enter if they are fitted with a vacuum breaker that is faulty.

I have solar panels on the roof of my house and twice I have traced the cause of the pool jets blowing bubbles to the vacuum breaker which is located at the highest point of the solar heating system.

The vacuum breaker allows air to enter the system allowing it to drain out when the pump is off. But this should only happen when the pump is switched off and no water is flowing through the solar heating system. In my case, it was faulty and was sucking air in constantly and producing pool bubbles, so I replaced it.

Other reasons for pool jets bubbling

If the air bubbles persist and still accumulate in the strainer then, unfortunately, it may mean you have a problem with the pipework from your pool skimmers and main drain to the pool pump. Much of this pipework is probably going to be under the ground and will probably mean you will need the assistance of a local pool contractor to trace and fix the problem.

If you have an above ground pool this won’t be such a big problem to fix since none of your pipework will be buried underground.

Air bubbles in only one pool return

It is not uncommon that you may have air bubbles coming out of one pool jet and not the other. The reason for this is probably the way the pipework has been installed and it is most likely that it is the nearest return to the pump that has the air bubbles.

Just go through the steps above to eliminate the bubbles.

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