So i built a 5' x 7' x 2.5' pond 5 years ago for this guy,. He bought the liner from home cheapo, those plastic flexible type... I installed the liner, rocks, pump, filter, etc. . so anyways.. no problems for 5 years. He calls me up to replace his old pump. No problems, i go over there take out the old pump ( it had about 4 feet of kink free tubing going into a 3/4" pvc pipe), drain about 5"s of water (water was about 40 degrees) replace the kink free and then lower the new pump to the bottom. Top off the pond and leave. He calls me that night and says "thank you for coming out so quickly" and "wow you took alot of water out of the pond" I think to myself hmmm i only left it maybe an inch lower than it was when i got there. Well the next day he calls again and says the pond is about 2/3 empty. SO i figure the kink free had a leak or something.. replace that again, and it still leaks. So Saturday I take the fish out of the pond and tell him not to do anything till Wednesday (yesterday). I check the pond and its fuller than when i left saturday, i call him and he said he filled it up to see if it would leak faster, said it water level hadnt moved in 12 hours. so i made a mark on the liner and filled it up about 4"s, and made another mark, I go over today and it went down about an inch. I checked yesterday at the level it was, for any cracks, tears, holes or anything that could cause water to vanish. NOTHING..... I dont know what else to do. Ive been to this guys house (30 miles round trip) 5 times since i put the pump in. No obvious fault of mine. And no visible problems. What should i do? Do i charge him anything? Do i tell him he is on his own and its his fault for buying a cheap liner and these things happen? Do i keep going over there till i find a hole and patch it? Does any body know about those "plastic" type liners? not the cheap preformed kind, just the semi stiff flexible type, I think its a beckett liner... Can those be patched like a regular liner? Thank guys....and gals.