Moved into our house about a year ago. Seller said the moisture ring around the hot water heater was condensation and was normal. Now it has gotten worse. It has spread, traveling under the wall to damage part of the ajoining finished room. Rust has also formed at the seam where the main portion of the tank and the base join. It's from that joint, not the pressure relief valve, like friends have said, where the water seems to originate from. Could this be the end? Also, should a hot water heater be sitting directly on the concrete slab?