Abstract: A closed loop geothermal heat exchanger in a heating and cooling system for conditioning the air in an enclosed structure comprising heat exchange coils disposed in the interior of an inground sealed tank external to the structure wherein inlet and outlet conduit provide for the inward and outward flow of water from an external source into and out of the tank and wherein the water within the tank is the geothermal heat exchange medium and further provides a domestic water supply for the structure and capped incoming and outgoing test conduits provide for water temperature and flow measurement and a removable sealed lid is provided on the tank top to access the tank for repairs and a support conduit is provided within the tank to eliminate residue build up within the tank top and enhance the mix of incoming and outgoing water temperature and an air gap is provided within the tank between the inlet conduit and the outlet conduit to eliminate back flow to the water source.