The Mysterious Vinyl Liner Leak

May 15, 2011
2
:wave: Greetings.. I own and 18 x 36 in ground pool. Replaced the liner 5 years ago with a 28 mil high quality liner. We have no drain at the deep end. Only 2 values.. I intake and out take, and the skimmer. We looked outside one day, and we noticed our water level had dropped may 6 inches. In less than a week in dropped 2 feet, to just below one intake value. There is not visable signs of liner failure. We called a plumber to pressure test the lines.. All fine. We filled it back up, did it again. We are getting ready to order a new liner, and replace. . But it seems odd that you would have this rapid water loss than just this slower draw down. Could we have some kind of erosion in the vinyl itself with using clorinating "pucks" in the skimmer basket. Would the pressure test have missed somehow a leak going through the waste line? We have so few great days here in Washington to take full advantage of the pool, this is such a waste...
 
Welcome to TFP!

You said it drained to just below one intake valve. Did it stop going down at that point? Or is that when you decided to refill? When there is a leak, you can let the water drain down until it stops, or at least slows down dramatically. The leak must be at that height. Usually you can search around the pool at that height and find where the problem is. In this case, if the leak slowed down at that height, it might be the seal around the intake valve where it connects to the liner.
 
The dye test for finding leaks uses small amounts of dye added right near where you think the leak might be and then you watch to see if the dyed water is drawn into a hole somewhere. It only works when the water is very still and you add the dye very close to where the leak is.

You can use food coloring. The concentrated paste dyes are better than the liquid dyes, but liquid will do in a pinch, it just isn't as visible.
 
To find a leak the best method is to get in the pool with a diving mask and a squeeze bottle of food coloring. Slowly go around the pool trying not to disturb the water squeezing out a small cloud of food coloring very close to the bottom/sides every few inches, start with suspect areas around fittings, seams, indentions, then around the edge of the floor, middle of the floor and walls last. For the shallow parts of the mask and snorkel work ok when your trying not to disturb the water, for the deep end scuba gear can make the chore a lot easier if you are properly trained in its use. In my experience 1 or 2 standard bottles of food coloring is enough to cover an entire pool. (if I need to buy it I usually just buy one of the variety 4 packs at the store, and start with the red).

Ike

p.s. when you find the right spot, it will tend to be very noticeable, usually the dye will swirl out and disappear in a whirlpool action, until then it will just sort of fade away into the rest of the water.
 
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