Many leaking cracks are so small they can barely be seen with the naked eye. But a squirt of dye can pinpoint the spot where water is flowing through them.
Many leaking cracks are so small they can barely be seen with the naked eye. But a squirt of dye can pinpoint the spot where water is flowing through them.

Back in the old days, leak detection hinged on a good eye and a syringe of dye. And while modern electronic equipment can be great for locating leaking pipes underground, precise observation and solid instincts still hold the keys to effective detection.

In fact, developing a reliable, thorough process for finding leaks comes with experience, and plenty of trial and error. But it’s never too early — or too late — to begin mapping out such a process.

When dealing with leak detection, it’s important to check a variety of factors. And understand that even when a leak is located, the process doesn’t stop there, because quite often more than one problem exits.

Scope out the area

Begin by observing the equipment while it is running. Are there any equipment leaks? Then check the waste line, and see whether it is equipped for water loss with the system running.

Next, turn the system off, and slowly walk around the pool, checking to see if any water is leaking through the wall.

Make a mental note of any unusual observations, such as previous patches, discoloring in the finish, or leaves stuck in the wall. Scan the deck for cracks that may continue through the coping and travel further through the tile and/or down the walls.

Are there any signs on the deck that indicate it has been opened for an underground repair in the past?

Ask questions of the homeowner, or whoever else is taking care of the pool. What observations have they made regarding water loss? How long has the pool been leaking? How much water does it lose in a 24-hour period? Does it lose more with the pump on or off?

These initial observations and questions will provide valuable information for the next steps of the investigation.

Begin the examination

Everything up to this point has been mental. Now it’s time to utilize the professional skills.

If you have access to an electronic listening device with a hydrophone, this is the time to use it. Place the hydrophone by the returns, the vacuum port and the main drain pots, and in the skimmer.

The turbulence created by certain leaks can be heard. If a high-pitched noise — similar to a jet flying by — is evident, it may indicate a problem in this area. (But remember to look up, as there may actually be an airplane overhead.)

Realize also that 90 percent of leaks occur where two different materials meet. Remove all eyeballs, vacuum port covers, main drain covers, etc. and dye test anything that looks unusual. Remember: “If it catches your eye, it may pull dye.”

Examine hard-to-see spaces by using a mirror and flashlight. If any leaks are apparent at this point, clean the area around the leak with a steel brush and prepare some two-part epoxy.

Repairs with epoxy

It’s important to check the epoxy’s packaging to ensure it’s a type that will harden underwater. Any swimming pool supply store should have this kind of epoxy on hand. It’s typically available in both white and black, so for aesthetic purposes, it may be helpful to mix equal parts of each color to create a grey substance that will be invisible on the pool’s finish.

The epoxy package will contain “Part A,” which is the resin, and “Part B,” which is the hardening agent. Cut two portions equally of A and B, and combine them by rolling the mixture into a ball until its texture and color are consistent throughout (gloves may be helpful for this step).

Apply the epoxy to the crack or around a fitting, smoothing it by applying fingertip pressure. If the leak is coming from behind the light niche, be sure to mix enough epoxy to plug up any holes at the back of the light and around the cord.

An alternate product is butyl tape, which is hand moldable, sticky and very flexible, and may be ideal for sealing a leaky light conduit around the cord.


The homeowner may have indicated that more water seems to be lost with the pump on, which means a few other checks may still be necessary.

Pressurize all lines to about 20 psi. Make sure that when plugging the lines, the plugs don’t cover up the problem. If the return line or pressure line fails to hold pressure, it’ll be necessary to use electronic devices to identify the exact location of the break.

A pressure rig should be capable of injecting water and air into the line separately. Inject water first to flood the area around the leak, creating a pool of water. When just starting to use the equipment, it is good practice at this point to drill a small hole through the deck or ground and send a rod down to make sure there is water present.

Next, inject air and listen through the deck using the headphones and electronics — try to pick out the bubbling sound that indicates air is escaping into the pool of water around the pipe. When the loudest sound is heard, mark the spot.

If water appears, it may be necessary to replace that section of pipe.

After the broken or cracked underground pipe is located using the electronic equipment, the area must be excavated, making a hole large enough to cut out the section of pipe. A coupling and PVC glue will be needed to repair the pipe.

A pressure test of the pipes is advisable before replacing the dirt and the concrete.

Only a licensed pool contractor or plumber should perform these repairs — especially if the pipe is located underground or sealed within concrete. Attempting such work without the proper training may result in serious damage to the deck or piping.

While these are only the basics of locating leaks in swimming pools, a process such as this can provide a foundation for success. To become an expert, one needs patience, determination, knowledge and the proper tools. The best tool, however, is always the one between your ears.