After repairing a lot of the indoor pipework between the loop and the machine, it now looks like I have a leak somewhere in the closed ground loop. We have two wells, each 300 feet deep, about 40 feet from the house. We'll have to wait for the spring to do any digging, and will probably start from the wells and move back towards the house. The main suspects right now would be the welded fitting where the pipe switches from horizontal to vertical, or the pipes between the wells and the house. Either would be preferable to a leak in the vertical portion. Is there any point adding dye to help locate the leak? I've never really understood why the dye would rise to the surface, and I'm not expecting a miracle. But if we're going to be uncovering the pipe anyway, would the dye create some kind of local staining in the ground around the leak? Thanks for your help !