Abstract: Recovery system for the recovery of thermal energy from waste water from building, which system comprises a heat pump adapted to absorb thermal energy from a non-freeze liquid circulating through the heat pump and arranged to deliver thermal energy to water flowing through the heat pump, a heat exchanger device that is in contact with said waste water, and a pipeline system disposed between the heat pump and the heat exchanger device, and in which non-freeze liquid can circulate. The heat exchanger device is designed so that the non-freeze liquid passes through the heat exchanger device, whereby the non-freeze liquid is able to absorb thermal energy from the waste water. Further, the system comprises a collector tank, and a pipeline system for supplying waste water to the collector tank. The heat exchanger device is disposed in the collector tank, wherein the non-freeze liquid can absorb thermal energy from waste water in the collector tank.