Swimming Pool Blog

Winter Pool Leak Detection

Winterized pool leak detection

by Rob Cox, January 13, 2012

leaking winter poosYour pool is chemically treated, cleaned and covered - all buttoned up for the winter. Then you notice (!) that your solid pool cover seems to be slipping lower and lower into the pool.

If you have a mesh cover, you won't notice this slipping, but peeking through or under the cover - and the water level is not holding.

This is a problem - needs to be fixed.


Winter pool leaks can be more trouble than a summer pool leak, and if not caught early - can easily lead to larger problems. Here's why:

1. Without the support of the water beneath it, solid pool covers can fall into the pool, with the weight of rain and snow.

2. Mesh covers also need the support of water beneath them, during a heavy snow load. When water levels drop more than 12-15" below a mesh pool cover, and a heavy load of snow or ice is deposited, your mesh cover straps and springs may become deformed or break.

3. For vinyl lined pools, if too much water leaks out, and the water level approaches the shallow end floor, the liner may relax and pull away from the pool and floor. The cold weather makes this worse, as it causes the vinyl liner to shrink and pucker. Above ground pools may also risk wall damage without the water pushing outwardly.

4. Plaster pools have a risk of popping out of the ground - if the pool empties completely, and the water remains underneath the pool. Pools that are built in low areas, topographically, are particularly susceptible to damage from hydrostatic pressure beneath the pool shell - which can be so great, that it can actually lift the pool out of the ground!

5. Excess water in the ground surrounding the pool can freeze and cause "deck heave". As water expands, it can lift slabs of concrete, which may fail to come back down level, and may rip any caulking or damage joints between deck slabs. Excess water can also erode supporting soil around the pool and under pool decks, and cause problem as fill dirt is gradually washed away.

Now that I have made a case for the importance of fixing winter pool leaks, let's talk about how to locate and repair common winter pool leaks.

Locating Winter Pool Leaks

1. If you have a solid pool cover - make sure that your pool cover pump is not pumping pool water through small holes in the cover, beneath the cover pump. This can be quite common, so be sure to rule this cause out. If this is happening, reposition the pump and refill the pool.

2. Pool lights can frequently be a source of leaks. If your pool water level stabilizes near the top of an underwater pool light, you should consider this a strong possibility as the leak source. Remove the lamp from the wall and pull it up on deck. Place pool putty or light cord stoppers at the point where the light cord exits the light niche, through the conduit. Refill the pool and test.

3. Vinyl liners can leak almost anywhere. If you suspect a liner leak, the layman's method is to inspect carefully around the current waterline, looking for anything that looks like a small hole. Also look for small bits of debris that have been sucked into a hole in the liner. Using a leak testing dye for pool leaks can help you verify by squirting a small amount of dye in the suspected area. If the dye is sucking out of the pool, patch the liner in this area and refill the pool. ...

4. If no obvious holes are spotted, inspect closely all the places where the liner was purposely cut - skimmer, returns, light, steps. The gasketing or the faceplates can develop leaks as the weather turns colder and the pool walls contract a bit.

5. Cracks in a plaster pool, although uncommon, would certainly be a good place to check for a leak. With water temperatures being very cold, it is likely that you may defer this repair until spring. Fill the pool as needed to keep the pool cover intact and to prevent any chance of the pool "popping" out of the ground.

Winter pool leaks are no fun to find and fix. The water is cold and so is the concrete that you lay on. It is important however to keep the pool full, for the reasons mentioned above. If you cannot locate it, and want to wait until spring, keep the pool filled with a garden hose during winter, and be sure to pump off solid covers promptly, until you can fix this winter pool leak - in the spring!