We just put up our ABG pool today (a gift but bought used). We filled it halfway with water, not even 18 inches, went to eat dinner and came home to discover a leak from the bottom of the liner. Is there any way to figure out where the leak is? We have stopped filling for now and marked the water line to determine how fast and how much water we are losing. The pool is 12'X30", metal pole frame, not in the original box so I'm not sure who the maker is. TIA!