The present invention provides improvements for heating and cooling of structures. In the exemplary embodiments reference is made to residential structures though light commercial buildings would be another option. The heat transfer systems of the exemplary embodiments are constructed and arranged as a way to provide supplemental heat transfer for geothermal systems. One improvement provided by the exemplary embodiments relative to current geothermal systems is the utilization of residential wastewater discharge as the heat sink. Another improvement provided by the exemplary embodiments relative to current geothermal systems is the installation method which can be performed at the same time when the geothermal system is being installed. By linking together these two system installations, cost savings should be realized.