A locally respected well man told me today to stay away from closed loops as they are "much less" efficient than open loops, and, he said they lose efficiency over time. Anybody heard that? He said he's replacing a large closed loop system (100 loops) that has been in place for ten years at an aquarium with an open loop system. It's next to a salt water estuary, so the ground water level can not be far from the surface. It's entering temp used to be 65, but is now up to 70, while ground water temps in this area run 55. I asked him what size the loops were, as I wondered if they were of too small a diameter, but he didn't know. Nor could he tell me how close together the loops were placed, as I believe that can affect the ground temperature. I should have asked about depth, but I doubt he would have known. He just said emphatically that the place wanted him to put in an open loop system immediately. Could it be the original closed loop system was sized wrong?