For the past few years I've had to turn off one of my skimmers because that line always takes in air somewhere. I always figured that the leak is somewhere underground and inaccessible but maybe I'm wrong. It's an old in-ground pool and filter but probably not the original filter; it looks like the hoses were rerouted to line up with the inputs/outputs. Is there any way to pinpoint where the air is coming from without busting up the pad around the pool? And if it is underground, is there any way to seal the leak- something like a pool version of antifreeze with StopLeak?