Your pool will naturally lose some water to evaporation, some to splash-out and some to backwash wastewater. You will also gain water from rainfall. The ordinary 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 that is worth spending some time and possibly money to repair.

Pools are meant to be watertight but sealants will deteriorate while other parts of your pool shift and settle or just plain wear out. Pools can leak through any of the fittings or accessories, plumbing, 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.

Leak detection is a highly specialized branch of the industry. Ninety five percent of all phone calls I get from worried pool owners about a leak turn out to be inexpensive to repair. So relax, if you can’t take care of the problem yourself a professional will be equipped to do so for you. If you suspect a leak, review the following things before calling for service:

Is the pool leaking only with the equipment on?

This 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. Check downhill from a pool, looking for weepers where underground leakage is surfacing. Check for soft or wet spots in the yard, on the side of the pool where the plumbing returns water to the pool.

Is the pool leaking only with the equipment off?

This usually indicates a suction-side leak, or on the pipes that bring water from the pool. 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 built up inside the filter tank. Use tape or a pencil to mark water levels.

Does the pool leak all the time?

This does not rule out leaks in the plumbing, but turns a suspicious eye on the shell of the pool, looking for cracks in the plaster or tears in the vinyl. Look closely at the tile line and look real closely inside of 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 with the pump shut off and water still to see if the dye is sucked into the crack. Under water lights can and do leak as well, especially 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.

Are there leaks at the equipment pad?

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 leak. If loss of water level is noticeable in the pool, it won’t be a drip, but a trickle at least.

Does the water stabilize at any particular level?

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. If the water continues to drop, we can rule out the skimmer (although there can always be more than one leak).

When the water stabilizes at any specific level, dye test and inspect around the pool very 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, to rule out the plumbing.

Are there any wet areas around the pool?

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 know where it’s going!

Unsure of your evaporation rate?

You can do the “bucket test” on your pool to measure evaporation. Place a bucket of water beside the pool and mark both the water in the bucket and the pool water level. Wait 24 hours then check the loss of both. If the pool loses more water than the bucket, then you have a leak.

Leaks in the underground plumbing?

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. It does happen occasionally, that a leak occurs at a pipe connector under the pool deck, or beneath the skimmer.

To determine if the pipes are leaking, the simple way is to shut off the pump and plug all the lines. If it keeps leaking, we know it’s not the pipes. If it stops leaking, the plugs can be removed individually to see when leaking continues, although some pools only leak with the pump running. Once narrowed down, a pool plumbing pressure test can be performed on the underground plumbing pipes, to see which ones are leaking.

Leaking cracks in the pool?

For concrete pools with surface cracking, most of these don’t leak, especially the smaller surface check cracks or shrinkage cracks on steps. But for larger and deeper cracks, these definitely can leak, and can be dye tested to verify. Cracks can be filled with pool putty, silicone or plaster mix to seal most small cracks. 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.

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