How to Detect a Leaking Swimming Pool

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Written by Eric

Last Updated: 11/12/2020

How to Detect a Leaking Swimming Pool

Summer season is here, and you and your family can’t wait to kick back and enjoy some quality time together in your backyard while you splash around in the pool to beat the heat. What can be more relaxing than having a problem-free pool day? Well, some of you pool owners out there may not be so lucky.

You may be wondering why your pool keeps needing to be filled frequently, or you might be noticing some strange water puddles around the pool or deck. These troublesome things could mean only one thing – you have a pool leak.

A pool can usually lose some of its water due to evaporation, splashing and wasted water due to backwash. Conversely, more water can be added from rainfall as well.  The basic principle is that if you’re regularly filling greater than two inches of water back into your pool every week, you likely have a leak that will probably require both time and money to repair. That’s where swimming pool leak detection comes in.

Pools are designed to seal water in. However, sealants can degenerate while the remaining parts of the pool can move, settle or just simply wear out. Pools tend to leak through most of the fittings, components, pipes, vents, or even through the pool walls. It is necessary to fix leaks, not just to conserve water, heat, and chemicals, but to also avoid damaging the pool’s other components and the washing away of the filling that holds the pool walls and deck.

Pool leak detection is a very specific part of the pool industry. You can find many different independent pool experts who are trained in leak detection in your local area or online. A major thing that many pool owners are concerned about is that leaks can turn out to be too costly to fix. But don’t worry, if you aren’t really prepared to do the job yourself, a professional can better handle the situation for you. If you think there’s leak, here are some important things to focus on:

How do you detect a swimming pool leak?

If you think your pool is leaking, there are many ways to confirm that:

  1. Mark your pool’s water level at the skimmer. Take a piece of tape or a pencil to make this marking. Look at the mark after a day. The pool should have a loss of no greater than a quarter inch per day. If not, there’s probably a leak.
  2. Fill a bucket with pool water and put it on the pool step. You should weigh it down using a rock or a brick. Mark the water level on the bucket, inside and out. You have to ensure that the levels are inside and outside are exactly the same. Observe the mark after a full day. If the decrease in the level is more significant on the outside of the bucket, a leak in the pool is confirmed. This test has to be done with your pump on, and again while the pump is off.

Is the leak happening only if the equipment is turned on?

If the pump isturned on, the pipe following the pump gets under pressure. That results in small drips being forced to turn into large gushers. You should look at the waste or backwash line to see if the water is constantly running. An inch of the pool water equates to 500 gallons. Look for soft or wet spots in your front or backyard, on either side of your pool where the pool water circulates.

What if it’s leaking with the equipment turned off?

This means that there is a suction-side leak, where the plumbing brings water from the pool. With the pump on, the pipes on the suction area are under vacuum. Air can be sucked in through these leaking spaces. You can find air in the pump basket if the lid is transparent, where air is seeping out of the return pipes, or air is consistently collecting in the filter tank. Get tape or a pencil to mark water levels for your swimming pool leak detection.

Does your pool leak frequent?

Frequent or consistent pool leaks tend to be due to the plumbing, but a more probable cause would be the shell of the pool, where there may be cracks in the walls or rips in the vinyl. Swimming pool leak detection in the tile line and a good look inside of the skimmers could also be a cause.The most common one being in a space between your plastic skimmer and a concrete pool. This is easily repaired using some pool putty. If you think you see something that resembles a crack, add some dye near it with the pump off and water not moving to check if the dye is pulled into the crack. Underwater lights can also be leak sources, mainly the conduit that goes from the light spot to the junction box. Using putty, butyl tape, or a cord stopper in the space between the niche and box can help fix this leak.

Does the equipment pad have any leaks?

You should take a good look at your filter, pump, heater, and valves, and even the floor for pool leak detection. Switch the pump on and off to check for water sprays while the pump is off. A little drip doesn’t have to be counted as a leak. If the water drop is significant in the pool, a trickle of water will be the more likely indicator than a drip.

Can the drop stabilize at any specific level?

You should be able to turn the skimmer valve off to help the water level fall below the skimmer, working the pump on the primary drain. If the water level still falls, you won’t have to worry about the skimmer. When the water levels out at a particular level, check around the pool closely at that point. Check for small particles that might have been pulled into the crack or space. This is a good way to know if there is a leak. Turning off the pump, and closing the drain, skimmer, and pipelines using some plugs, is another test for swimming pool leaks in the plumbing.

Are there any wet areas near the pool?

Detect a swimming pool leak around the pool deck and in the gap of the pool and equipment pad to see if there is any wet soil or erosion. If the pool has a downward slope climb down the hill to check if you can see water leaking from the side so you get an idea of where it’s going. If you can see water leaking around the pool and making puddles or wetting the soil, especially between the pool and pad, then you’ll want to have it checked as soon as possible. Otherwise, you’ll have to deal with erosion and other hard-to-manage issues.

What about a pool lined with vinyl?

Vinyl linings around your pool bring other things into consideration. If some animal made the sad mistake of falling into your pool, you might see some claw marks just under the water line. Taking time to look below the water using a mask can help you find a small leak in the vinyl liner. When pool liners wither down they can form pinhole leaks as well. While there is a possibility of having more than one leak, there’s usually just a tear in the liner, about an inch long, that should be easy to fix using a vinyl patch kit or some transparent vinyl sealant. Even slashes as long as 18 inches are pretty simple to fix, though they may not look the prettiest afterward. Clear vinyl patches can be used to repair these gaps but you should know that they tend to become yellow with time. You can also take a piece of liner sample, or cut-outs of the skimmer, drain, steps, or lights, from which the liner was put in. Another option is the using transparent sealers from EZ or Anderson to seal and fill up the cracks or gaps by just using your fingers to spread the gel from the tube.

Are there leaks in the underground plumbing?

The majority of pool leaks don’t come from underground plumbing. That said, a large hole coming in and ripping up your pool can be the worst thing to imagine as a pool owner. It can sometimes happen when a leak pops up at a pipe junction below the pool deck, or under the skimmer, but the fixes don’t usually involve a backhoe.

To check if the pipes are leaking, the best way is to turn off the pump and close all the lines. If it continues to leak, the pipes can be ruled out. If it doesn’t continue leaking, the plugs can be taken out one by one to find where the leaking occurs, even though some pools only leak with the pump on.

Once you have figured that out, a pool pipe pressure test can be used on the underground plumbing to check which pipes have a leak. A pressure test rig or stick can be used to check each line and see whether they can maintain pressure. Professionals can also add air into the pipe, and use headphones and a large stethoscope, look for the sound of the air leaking out from underground.

With this method, all they have to do is mark an “X” on the ground, or label the deck or yard to know where to dig. In many situations, a simple 3×3-inch hole can be made in the deck, to fix the leak. It isn’t common for the entire length of pipe to be replaced, and if that is the case, the whole pipe would be thrown away, and a new pipe put in as the replacement.

What about leaks in the tile?

With concrete pools that have conventional perimeter tile bands around the waterline, leaks are most commonly seen inside the skimmer. In other rarities such as a pool bond beam breaking under the tile, and also causing the tile itself to crack, pools can leak water through a void at the top of the pool wall. These cracks in pool tiles can be cleaned, aired out and fixed using EZ Patch 22.

What about leaks in the pool itself?

With concrete pools that have surface cracks, many of them don’t leak, specifically the small surface cracks or shrinkage cracks over the steps. That said, in case of bigger and deeper cracks, there can very likely be a leak, and a dye test can be done to confirm this.

Cracks could be fixed using silicone, pool putty or plaster products to fill them in. Bigger cracks present along the walls or across the pool would require greater effort and a two-step fix using injected sealant and then a finish of plaster material.

What about a leaking pool skimmer?

Almost all dug-in concrete pools can get leaking issues at the skimmer junction at some point in time. Increase and decrease in size of the pool and deck shifts the skimmer slightly, damaging the cement seal present in the pool wall and the skimmer. The seal is on either side as well as the rear of the front of the skimmer and can be tested with the pumps off and using dye to see if the water is being sucked into cracks present at the front section of the pool skimmer opening. Furthermore, pool putty is commonly needed as a time-being fix to fill up leaking concrete skimmers.

For a better permanent fix, remove all the plaster and put some EZ Patch 1 in its place. Vinyl pool skimmers can also show signs of leakage at their seal junction with the pool wall. Take a big #3 Phillips head screwdriver to securely fix in all the screws near the skimmer faceplate. Find substitutes for the skimmer gaskets with the skimmer faceplate in case the leak doesn’t stop. Dye tests can be done near the vinyl skimmer faceplates to confirm leaks when the pump is off.

Should you deal with detecting a leak yourself?

Since pool leaks can be difficult to find and hard to check, you may need a service professional who may need to make more than one visit to get an accurate diagnosis and fix it for you. These visits could cost as much as $100, and can obviously be even more if you have a severe problem that needs concrete cutting. That’s why it’s ideal to check for the leak as soon you can in order to fix it before the issue gets even worse and ends up costing you more money. Ideally, professional leak detection can help save you time and money since you’ll be able to find and even repair the problem yourself when you notice that your pool is losing water.


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