Ah, the dreaded, elusive pool leak. Pool leak detection is a highly specialized branch of the industry. Thankfully, almost 95% of all phone calls we get from pool owners worried about a leak turn out to be simple, inexpensive repairs. So relax! If you can't take care of the problem yourself, a professional is equipped to do so for you. If you suspect a leak, review the information below before calling for service.

How can you tell if the pool is leaking? Your pool will naturally lose water from evaporation, splash-out, and backwash wastewater. You will also gain water from rainfall. But the general rule of thumb is that if you're routinely adding more than two inches of water to your pool per week, you probably have a leak worth spending some time, and possibly money, to repair. Not sure how much water you're losing? Use tape or a pencil to mark water levels.

Pools are meant to be watertight. But sealants deteriorate over time, while other parts of your pool shift and settle, or just plain wear out. Pools can leak through fittings, accessories, plumbing, equipment, or even right through the shell. It is important to repair leaks, not only to save water, heat, and chemicals, but also to prevent undermining pool structural components and washing away fill dirt that supports the pool walls and pool deck. So how do you find a leak in your pool? Keep reading to find out!

Detecting a pool leak while the pump is running may indicate a pressure-side return leak. With the filter pump on, the plumbing on the pressure side (after the pump) is under pressure. This can open up small drips into spraying gushers. Check the waste or backwash line for water consistently running. One inch of your pool water can equal 500 gallons of water loss! Check downhill from the pool, looking for weepers where underground leakage is surfacing. Check for soft or wet spots in the yard, on the side where the plumbing returns water to the pool.

Pool leaks that pop up when your pump stops running usually indicate a suction-side leak, involving the pipes that bring water from the pool to your pump. With the filter pump on, the plumbing on the suction side is under vacuum. Air can be drawn in through otherwise leaking voids. You may notice air in the pump basket (if you have a clear lid), air bubbling out of the return lines, or air repeatedly building up inside the filter tank.

This does not rule out leaks in the plumbing, but turns a suspicious eye on the shell of the pool. In these scenarios, look closely for cracks in the plaster or tears in the vinyl during the pool leak detection process. Thoroughly inspect the tile line, and look carefully inside the skimmer(s). The most common leak we fix is a separation between the plastic skimmer and the concrete pool. This is easily fixed with some pool putty. If you see something that looks like a crack, drop some test dye near it while the pump is off and the water is still. Look carefully to see if the dye gets sucked into the crack. Underwater lights can — and do — leak, as well. Leaks are especially common around the conduit that runs from the light niche to the junction box. Filling the opening of the conduit in the back of the light niche with pool putty, black butyl tape, or using a cord stopper are ways to fix this problem.

Look closely at the filter, pump, heater, and valves. Check the ground for moisture. Turn the pump on and off, looking closely for spraying water when the pump is turned off. A small drip or two will not be the source of the primary leak. If loss of water level is noticeable in the pool, it won’t be a drip, but a trickle at least.

You may be able to close the skimmer valve and allow the water level to drop below the skimmer, running the pump on the main drain only. However, we recommend using a submersible pump instead, to avoid any risk of pool pump damage. If the water continues to drop, you can rule out the skimmer (although there can always be more than one leak).

When the water stabilizes at any specific level, use a pool leak detection dye test and inspect around the pool carefully at that level. Look for small debris which may have been sucked into the crack or void. This is a good indication of a leak. If the water stops at a wall fitting, wall step, or pool light, give it a good, close look. Shutting off the pump, and plugging the drain, skimmer, and return lines with expansion plugs, is another test you can use to rule out the plumbing.

Take a walk outside the pool deck and between the pool and the equipment pad. Check for wet soil and eroded areas. If your pool has a downhill slope near the pool, walk down the hill to see if you can notice water weeping from the hillside — at least you'll know where your missing water is going!

Dealing with a leak in your vinyl liner pool? If so, there are special considerations. Look for sinkholes where sand under the liner may have washed away. Look for tears or separations around all fittings: skimmer, returns, cleaner line, steps, pool lights, main drain, etc. Pay close attention to steps and corners, where the liner may be stretched more than normal. If an animal had the misfortune to fall into your pool, you may notice claw marks (tears) just below the water line. Spending time underwater with a mask may be required to find a small leak in a vinyl liner. When pool liners become old, they may develop pinhole leaks easily.

There can always be more than one leak. But most of the time, it’s a gash in the liner, about 1” long, which can be easily repaired with a vinyl patch kit, or with clear vinyl sealant. I have successfully (though not beautifully) patched liners with gashes as long as 18” before. You can use clear vinyl patch material, which tends to yellow over time, or use a piece of liner sample, or the skimmer / drain / step / light cut-outs, from when the liner was installed. Or use the EZ Patch 28, or Leakmaster Flexible Sealer, which are gels squeezed from a tube, then smoothed over the area with your fingers.

You can do the “bucket test” on your pool to measure evaporation and determine if a leak is present in your pool. Place a bucket on the step of your pool, making sure the water level is the same both inside and outside the bucket. Mark the water level in the bucket and the pool water level on the outside. Wait 24–48 hours, then check the loss of both. If the pool loses more water than the bucket, then you have a leak. If both levels remain about equal, you're likely only dealing with evaporation.

Most pool leaks are not in the underground plumbing. Although, it’s every pool owner’s worst fear — a large backhoe coming in and ripping up the pool deck. But occasionally, a leak occurs at a pipe connector under the pool deck or beneath the skimmer, but the repair rarely involves a backhoe.

To determine if the pipes are leaking, the simple way is to shut off the pump and plug all the lines. If the pool keeps leaking, we know it’s not the pipes. If it stops leaking, the plugs can be removed individually to see when leaking continues. However, keep in mind that the pool may only leak with the pump running and the lines under pressure. Once you've narrowed down which line(s) it may be, a pool plumbing pressure test can be performed on the underground plumbing pipes to see which ones are actually leaking.

A pressure testing rig or stick is used to test individual lines, to see that they hold pressure. Experts can also introduce air into the pipe, and with headphones and a listening device, listen for the sound of escaping air from an underground leak. In this way, they can literally draw an “X” on the deck or in the yard, saying "your leak is right here."

In most cases, you can simply cut a small 3’x3’ hole into the deck to repair the break. Very rarely does the entire run of pipe need to be replaced. And even if it did, it would likely be abandoned, and a new pipe run in its place.

For concrete pools with the traditional perimeter tile band at the waterline, leaking is most often found inside the skimmer. In rare cases where the pool bond beam cracks behind the tile, and also cracks the tile, pools can leak water through a crack in the top of the pool wall. Cracks in pool tile can be cleaned, dried and filled with EZ Patch 22.

For concrete pools with surface cracking, most of these don’t leak, especially the smaller surface check cracks or shrinkage cracks on steps. But larger and deeper cracks can definitely leak, and should be dye tested to verify. Most small cracks can be filled with pool putty, silicone, or plaster mix. Large cracks running across the pool or down the walls will need more prep and a two stage repair of injected sealant, followed by a finish coat of plaster mix.

Nearly all inground concrete pools will develop leaking problems at the skimmer throat at some point. Expansion and contraction of the pool and deck moves the skimmer slightly, breaking the cementitious seal between the pool wall and the skimmer. The seal is on both sides and the bottom of the front of the skimmer, and can be dye tested (with the pump off), to determine if water is being drawn into cracks around the front edge of the skimmer opening. Pool putty is often used as a temporary repair to seal up leaking concrete wall skimmers. For a more permanent repair, chip out the plaster and fix it with EZ Patch 1.

Vinyl pool skimmers can also begin to leak water where they seal up to the wall. Use a large #3 Philips head screwdriver to tighten all screws around the skimmer faceplate, very tightly. Replace the skimmer gaskets for the skimmer faceplate if leaking continues. Dye testing can be used around vinyl skimmer faceplates to verify leaking (with the pump off).

Leak Testing

Expansion Plugs

Flexible Sealer

Pool Putty

Pool Plaster Patch

Cement Sealant

Silicone Sealant

Skimmer Gaskets

Vinyl Patch Kit

Vinyl Sealant

Surface Preparation and Repair Products