I found this forum and signed up in desperation, this morning. My pool guy (who opens, closes, and addresses my pool problems) is unable to fix a leak that started last July 2. Does someone know a "fantastic at detecting and FIXING" leaks person or company in the DC area? I'm in Arlington, VA, my pool is 20,000 gallons, has a vinyl liner over foam and a cinder block base (liner was replaced 2 yrs ago); the leak started after the torrential rains we had last July. My pool guy pressure tested the lines (Polaris, intake and return), and did the electrical, "where does the current go following a leak" process (no useful results). He thought the light receptacle was the problem, has resealed it twice, most recently a month ago. The level held until yesterday when I connected the Polaris. The leak began again last time I restarted the Polaris (in the fall), but he swears the Polaris is not causing the leak. He just replaced the xeobrite in the sand filter yesterday (it was 6 yrs old, he says early to replace it but it was not clearing the water) and probably because given the leak problems, low water level, I'd had huge algae problems too, which I've never had before. I've had this pool since 1994, never had these ongoing problems earlier. HELP?