Please help me solve this leak

[cma20]

Our inground pool is 18' x 48' x 10' deep. It has a liner.

I have been fighting a huge leak for almost a year. Last summer, we lost 4 inches of water every single night. At the end of the season, we let the pool just leak until it stopped. It stopped 4 inches below the light and did not move from that spot for months. A pool expert came over to assess the situation and immediately said the leak had to be in the drain line or in the liner. He did a dye test all around the pool and decided the leak was not in the pool.

Going on the assumption that the leak was in the drain line, this weekend, I drained all the water out of the pool. I plugged the drain, connected a pressure tester to the drain line and just knew that I would finally find my leak. I would simply cap both ends of the drain and fix the leak.

To my absolute shock (horror and continued despair) the drain line is holding the air pressure. I can't believe it. I am totally at my wits end with this. Professional leak detection told me to expect anywhere from $800 to $2000 for them to find the leak last summer. This should not be rocket science and should not cost this much to find the stupid leak.

If the liner isn't leaking and the drain is holding air pressure - how could we be losing hundreds of gallons of water each night - and literally see no signs anywhere of water in the yard or the area around the pool?

Can someone please help me?

 

[JasonLion]

Sadly, locating a leak can often be a real pain.

It is possible for ground water to prevent the pool from draining down all the way, so that a leak stops before the water gets down to the level of the leak. I suggest looking closely around the main drain, to be sure the liner is properly sealed to the drain fitting.

Also, if the expert came more than a couple of weeks ago, fill the pool half way and see where it drains down to now, and if that is the same height as where it drained down to last time.

 

[Donny]

4 inches below the light ?? Hmmmm. How about the light housing itself ?? The leak should be above the lowest point the water stopped. I would go around the pool and look very closely at the liner as well.

 

[Kiss4aFrog]

I don't want to fight but the leak should be at the level of the water. If you let it drain until it stopped then the leak should be at that water line.
If the bottom drain was leaking it would be leaking underground but at that level.
It sounds like it was well below the skimmers and the light but was it below the returns?
Is it 100% liner or do you have fiberglass steps or anything else ??
If you can, posting a few pictures of the pool might help.

Please add your pool and equipment info to your signature as outlined here - > http://www.troublefreepool.com/content/165-getting-started

 

[fnc1962]

Have you checked the static relief valve that is in the main drain beside the drain valve, check around the light housing? I had a leak last year, spent over $500 to get it diagnosed and patched.No telling how much in water and sewer costs, probably a few hundred anyway. The pool store made several trips, performed 2 pressure tests, changed the static relief valve etc., etc. It ended up being a crack in the eyeball return just in front of the threads, that's why it would not show up in pressure tests. A little 5 minute epoxy patch is what it took to fix the leak. Just my experience with it anyway. Hope it helps! Good Luck!!!

 

[cma20]

Thank you for all these comments. I'll address them all here.

Light housing. My pool expert resealed the light because we were at one point, sure that the leak was in the light. It wasn't. The leak went on another 4 inches below the light. The level at which the pool stopped leaking is well below the skimmers, the returns, the light - everything. The water level stays above the steps where the vinyl liner meets the steps, plus a dye test was performed around the steps and came back as no leaks.

As an update....this morning, I found that we did in fact lose air pressure overnight. We lost about 20 pounds. This would indicate that the leak is indeed in the drain line.

Based on the advice here, I am going to look closer at the drain looking for cracks, etc., in case the ground water level suggestion has bearing. I am going to refill to above the light and see whether I have fixed it by capping off the drain.

Thanks again for all of you taking the time to look at my post and respond. Really love this website!

 

[swimcmp]

CMA loosing pressure overnight tells nothing. Temperature change could create your pressure loss. If it really was the main drain line you should see a loss in a short time. If it holds pressure for more than an hour keep looking. My guess is a pinhole in your vinyl.