I have a small pond that was installed prior to my purchasing our house. It has a plastic liner, and for the last two winters, including this one, it has spontaneously drained itself to within 5 inches. Last year I was able to refill it once it warmed up and it held water all summer. Well now, it just drained itself again, so I'm wondering, is there a way to find a leak that behaves this way and if so, can it be sealed. I have a picture of it, but I don't see a way of posting that here.