Possible Leak?

Leaks in the pool, plumbing, filtration system, skimmer, ...
Finding & repairing swimming pool leaks.
Jack Sparrow
Pool Enthusiast
Pool Enthusiast
Posts: 24
Joined: Mon 30 Jul, 2007 20:33

Possible Leak?

Postby Jack Sparrow » Sat 04 Oct, 2008 18:35

The liner in my in ground pool is coming up in one small area. When you step in this area you can feel there's water under it. When this happens is this definitely a leak or could it be ground water? We're on a septic system here.

The pool (16x32) is winterized and covered but yet is still loosing water at a rate of 1/2 inch in 5-6 days. In the summer I wouldn't be concerned, but with the pool now covered I question it. Is there still evaporation with a covered pool?


Water under liner/Water loss

Postby Guest » Mon 24 Nov, 2008 14:12

Water under the liner: Unless you live in an area with a very high water table, you should not generally have water pooling under a liner from ground water. - not with enough force to actually bubble up the liner itself. Normally, the weight and pressure of the water inside of the pool will prevent this from happening. From your description, I am assuming that you either live in a clay soil area, with the resultant slow/poor drainage rates, or you have a solid floor under the pool ... in either case, I would say you definately have a pool leak - most likely (since the pool is winterized and I am assuming the underground lines are plugged off - with the exception of the main drain of course) a leak in the liner itself.

1/2 inch in five days "could" be evaporation, but it depends on a lot of factors. first and foremost the type of cover. Any type of mesh or porous cover will continue to allow some amount of evaporation. though much lessened over an uncovered pool. With any type of solid, non-porous cover evaporation should be practically non-existent. If direct sunlight heats the area under the cover and causes any evaporation of the water, it usually beads on the underside of the cover, cools and drips back into the pool. Second, the weather ... any type of precipitation in the area will be adding to your water level. Rain, drizzle, mist and even fog will all add some water to a pool - since they are all moisture. If you are stiol losing water with "any" of these present ....

The bubbling of the liner is the real clue though ... with clay soil or a dense floor that doesn't like to pass water easily, any water that passes through the liner faster than it will pass through the underlying soil, will "pool" Not being able to move down into the soil, it remains pretty much at the same pressure as the water inside of the pool itself and can form a water bubble beneath the liner. I say "can" because a bubble can also form when water being injected between the liner and the pool wall under pressure. In this case, there is often a leak in the inlet fitting either at or right behind the wall where the fitting is installed. The water is being forced behind the liner faster than it can drain away.

This one can be a really fun repair (and I mean that sarcastically - believe me). Ideally, the idea is to find the small cut, hole or pinhole in the liner itself, repair it and wait a few days. If the water does drain into the surrounding soil (at all) the bubble will disappear on its own. If not, then the water will need to be pumped out, which requires a portion of the liner to be loosened at the tracking and a hose or poly pipe or plastic tube forced between it and the wall into the "bubble" so a pump can draw it out.

The problem can be with locating and identifying the leak. If there is sufficient water built up behind the liner it can "back-up" - filling the space behind the liner to the same level as the pool water. You may not be able to detect it with the liner in place, but it does happen. If this is the case, then the leak essentially "stops" or slows drastically, only leaking from the pool as fast as the water behind the liner seeps through the ground and away. In this case, the only way to really identify the leak - unless you are lucky enough to physically "see" it, is to drain the water under the liner first. Then look for the leak when it will be passing water at a greater rate. (By contrast - the closer the pool water level gets to the leak the slower the water loss will be.

In any case, My best guess is that you do have a leak. Most likely a surface leak in the liner itself, or around a fitting. The water will continue to go down until it reaches the level of the leak/hole and there it will stop. The real hazard here depends on the location of the leak itself. If it is high, it could ultimately be something that can wait until warmer weather to for repair. The main danger here being that as the water level goes down (and the water pressure decreases) the "bubble" size can increase, stretching the liner itself, in the area of the bubble, and making it so it will wrinkle when it flattens back out again.

If the leak is low enough - even though it may still be above the floor of the shallow end, it could allow for liner shrinkage. It is the volume and pressure of the pool water that actually pushes a liner into shape and maintains it against the pool walls. Should the pressure lessen enough to allow the liner to shrink or shift, it may not stretch back into place properly when the pool is refilled. Believe it or not, Both a new or an older liner will likely survive this more readily than a middle aged one - being old and having been in position so long, an old one tends to not shrink or distort as easily. A really new liner often have enough pliability and stretch to either go beck into position on it's own or can be "coaxed". Middle-aged liners, those more than a year or two old and still having "some" pliability, can still shrink or shift but don't stretch back as readily and are not coaxed as easily .... these are the puppies that are most likely to split trying. (NOTE: there is even more danger of this happening, of course, if the leak is somewhere in the deep end and the shallow end goes completely dry.

The final nightmare with a liner leak at this time of year occurs "after" the water freezes. Ice, once it forms and spans a pool, can literally support/suspend itself while the water beneath it continues to drain away. What you end up with is a surface of ice over open air between that and the actual surface of the water. Should this happen, there is the possibility of it completely destroying the liner should it suddenly collapse.

Horror stories done, in my honest opinion - based on your description - you likely have a leak in the liner itself.

I have worked in pool repair for 25+ years and have seen similar situations.

-- Ray --

Possible Leak?

Postby Guest » Wed 18 Mar, 2009 08:11

The pool is winterized and covered but yet is still loosing water at a rate of 1/2 inch in 5-6 days.

Sounds like a leaky liner or plumbing to me.

If the winterizing plugs are all in place and you're still losing water then your liner has been compromised.

Return to “Swimming Pool Leaks”

Who is online at the Pool Help Forum

Users browsing this forum: No registered users and 0 guests