I have a 5 year old inground vinyl pool, 8 feet deep, losing approximately 2-3 inches a day. Starting leaking much worse after i turned the skimmers off and ran on just the main drain. Had a diver check the pool: nothing. Turned everything off and over 4 days it leaked to about 3 inches below the jets and lights, so the only thing was the 2 main drains. I put plugs in those. Still leaking; it may have stopped now that it has reached the skimmers…will see. My skimmers only have 1 opening, so i am uncertain how those two could possibly be connected. Right before the pump, i have a main drain valve and separely i have the skimmer valve. There are white plugs in the bottom of the main drains and in the extra hole in the skimmers. The plugs have a square indent presumably to take them out…i do not believe they are hydrostatic valves. I have a sump pump under the deep end of the pool. Thank you so much for any advice…at a loss