Pool leaking and bubbles at the drain

My pool is leaking! What should I do?

Ah! I think the pool is leaking! There’s nothing worse than looking at the pool and wondering why you’re having to top it up so often. Is it the weather? The water temperature? Or, (worst case scenario), is there a leak? It’s normal that pools can lose water quite rapidly, especially in summer. This makes it tricky to determine if you really have a problem or not.

Here in this article you will learn a few tests you can do that will help you work out if there is a problem with your pool.

Let’s investigate!

Pool leaking guide table of content:

Start With The Bucket Test

The bucket test always comes first when trying to work out if you have a leak.

It will tell you whether any water loss is due to evaporation or due to an issue with the pool.

Bucket test in a leaking swimming pool

Steps for the bucket test

  1. Grab a bucket and put it on the top step of the pool with the water level in the bucket at the same height as the water in the pool.
  2. Leave it for a few days (it doesn’t matter if it rains) and keep everyone out of the pool. Run the pool normally and don’t backwash the filter.

If the water in the bucket after a few days is higher than the water in the pool, then there’s a problem. If the water is still the same height in the bucket as the water level of the pool then there’s no problem. 

Bingo. Stop reading here.

No steps in your pool? No worries

If your pool doesn’t have steps don’t worry – you can still do the bucket test.

  1. Sit the bucket on the deck or ground next to the pool.
  2. Mark the water level in the bucket with a marker pen and then mark the water level in the pool – if you don’t want to use a marker pen on your skimmer then try a piece of tape.

You want the water level in the bucket to go down (or up if it’s been raining) at the same rate as the water in the pool. Both the bucket and pool will evaporate at the same rate, and the rain will top up both the pool and the bucket at the same rate. 

If the pool goes down faster than the bucket, you’ll need to do some further investigation.

Next: Inspect Your Pool Equipment

Now’s a good time to check in the pool pump shed, after it’s been running for a couple of hours.

  1. Look for any traces of water around the bottom of the pump.

This may indicate a leaking mechanical seal (it usually keeps the pool water away from the pump motor). Also check where the pipe is attached to the pump for leaks.

  2. Next, check the pool filter.

Make sure there’s no leaks around where the valve on the top of the filter joins the filter tank if you have a media (or sand) filter.

Check the unions where the pipes join the valve for drips.

  3. Then check where the backwash pipe empties into the waste water trap.

If you can see water dripping out of the backwash pipe when the filter is set to “Filter” then you’ve probably got a problem with your valve seat gasket or spider gasket in the filter valve.

It’s the gasket that is meant to stop water going where you don’t want it to go when you change positions on the valve handle.

You might need to contact your pool shop to fix that one!

  4. Then check for leaks on any other pieces of equipment you may have like salt chlorinators and heat pumps.

Heat pumps can be tricky to check because of the water that drips out of them while they run. Thankfully there’s two easy ways to check if the heat pump is leaking.

You can either turn it off for a few days and the drips should stop or get your test strips and check the water for chlorine. If the heat pump is leaking then there will be chlorine in the water.

If it’s just the condensation dripping off the heat exchanger then there will be no chlorine in the water under the heat pump. A little leak adds up over the pump’s daily run cycle.

My Equipment Is Fine And The Pool Is Still Leaking!

If you found a problem when you did the bucket test and couldn’t find an issue in the pump shed then it’s time for the next checks.

The bubble test

Have a look at the eyeball returns (the jets) where the water comes back into the pool. There shouldn’t be any bubbles in the water coming into your pool, unless you have an Ozone system

If you have a solar heating system, these may produce bursts of bubbles when they start up, but these should clear quickly.

If you do see bubbles when you shouldn’t, you may have a leak on the suction side of the pump. It must be sucking air in somewhere to produce bubbles. It could be simple, like an issue with the O ring on the pipe connection at the front of the pump, or the O ring under the pump lid. 

These do need greasing up from time to time (use a silicon-based lubricant, not Vaseline or a petroleum-based grease for better O ring longevity). They may also need replacing. If the O rings are leaking, the water won’t go down when the pump’s running, but the water may leak out of these O rings when the pump’s turned off depending on where your pump is in relation to the pool’s water level.

If you have an Ozone unit, you can try this test as well once you’ve blocked off the hose between the Ozone generator and the injector in the pipework.

If you’ve checked all these and can’t find anything, contact your local pool shop – you’ll probably need a technician.

It’s All Working, But There’s Still An Issue...

For the next test you’ll need your bucket again.

  1. Set the bucket up like you did for the bucket test, but turn the pump on continuously for 2 or 3 days, 24 hours a day.
  2. Then check the bucket. If there is a noticeable difference in the water level in the bucket to the pool water level then there may be a problem in the pool’s return line.

That’s the pipe coming out of the top of the pool pump, through the filter, salty, heater etc and back to the eyeball returns.

The water is being pushed out when the pipe is pressurised.

If you’re confident that there are no leaks in the pump shed then it’s probably time to call the technician in.

They may need to pressure test the return line to make sure there’s no leaks underground somewhere.

You could also have a leak in a penetration through the pool lights, hydrostatic valve, skimmer box or eyeball returns.

At this stage we’d also recommend getting the technician in and they can do a dye test to isolate where the leak is.

How Long Will It Take To Fix?

Fixing leaks can be very time consuming with tests that are carried out over the course of several days.

Keep in mind that unless it’s a simple fix, the diagnosing of the issue can take a lot of time.

By following the steps above, you can hopefully isolate where the issue is which will help reduce the workload for the technician if you need to call them.

It’s a good idea to keep records of what you’ve done to show them if you need to call a technician in. That way, they may not need to repeat some of the tests.

You might also want to check our article on how to find a pool leak

Good luck!

About the author
Adrian Hill
Adrian Hill

Hey! I'm Adrian, founder and pool expert here at Dolphin Pacific. I love spending time with family, fishing, and have been known to brew my own beer.

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