Hello all, hoping there might be someone that could make a suggestion that I haven't already looked at.
This is my third season with my pool. The pool itself was installed in the fall of 2013. Once the liner was set, my pool builder had water trucked in to fill the pool and immediately closed the pool for the winter. As exciting as it is to get a new pool built, I obviously couldn't help myself from looking under the cover from time to time that first winter. It was shortly after the cover was installed, that I noticed the water level had dropped significantly. I immediately notified the builder when I discovered the leak and he stated he would address the issue in the spring when he opened the pool for me and tested all the plumbing. Fast forward to spring of 2014. That April, the pool builder came out and removed the covered. The water had leaked out to just above the bottom gasket going around the stairway. Coincidentally, it was also at the middle of the light niche. No other breaks in the liner from pool items at this level. So the pool builder resealed both the light niche and the stairs and filled the pool back up. That first summer, I expressed concern over how frequently I needed to keep adding water to my pool (several inches per week). I did several bucket tests with marginal results in determining if the pool was still leaking (it was almost impossible to keep my kids out of the pool that first summer so a successful test was difficult to obtain). Anyway, in the fall of 2014, I invested in a cyclone blower and closed the pool myself.
January of 2015, after being away for a weekend and forgetting to put the pump back on my pool cover, we had a weekend with heavy rain while i was away. I came home to a corner of the cover that had come loose and I took the opportunity to take a look into the pool, and to my surprise, the water was back down to the bottom of the stairs/light niche mid point again. I immediately notified the original pool builder and was told that he would be out in the spring when the weather broke. Again, spring time came and he again took a look at the steps and light niche. We filled to pool back up and after a couple successful bucket tests found that the pool was still leaking. This time, the builder contracted a leak specialist to come and use and acoustical device that could detect the leak. They stated that the leak was in the stairs and my pool builder again did some work on the steps followed by confirmation from the leak specialist that the stair were no longer leaking. The leak itself seemed to slow down after that and so I never really gave it much of a second thought even though I was still topping off my pool regularly. Last fall (2015), I closed the pool again in September. After about a month, I noticed that the cover appeared to be sagging really low so I pulled it back to find that the water was again down to the bottom of the stairs/middle of the light niche. I again notified the pool builder and again he stated he would be out in the spring.
Fast forward to March 2016. I got an early jump on the pool builder so i could get him out to look before he was backed up with his spring work load. He came out, pulled the entire light out of the niche and did some repairs (since he repaired the stairs twice already). I put a few inches of water into the pool and covered it back up. I waited two weeks and pulled the cover back to find that the pool had lost water yet again. So its obviously still leaking.
I'm lost as to what action to take next. The pool always drains down the the same spot. I've pressure tested the main drain line by air locking the pipe after blowing out the line with my cyclone and it holds pressure. Again, the only breaks in the liner at that level are the light and the stairs. I'm pretty much fed up with dealing with this leak at this point. I'd hate to go the legal route since I have a very cooperative and responsive pool builder. Whenever I call, he always responds so its not like he has just left me high and dry (for lack of a better term). He has even stated that if he can't find the leak, he will replace the liner, water and chemicals at no cost to me, but he wants to rule out any other possibilities as to the source of the leak so that he doesn't go buying a new liner only to find that the new one starts leaking as well.
I'm just looking for some suggestions from others in case they have ever had an issue like this. Want to be certain I'm not over looking something that could be the source of my leak. Its been almost three years since investing a lot of money into a pool build and I still don't actually have a pool that holds water.