A recovery system for the recovery of thermal energy from waste water from a building, which system comprises: - a collector tank - a supply pipeline system (10; 110, 126; 210, 210a; 210, 210b, 226) for supplying waste water to the collector tank - a heat pump, - a heat exchanger device arranged in the collector tank and which is in contact with said waste water, - a heat transfer fluid pipeline system arranged between the heat pump and the heat exchanger device, - the heat pump is configured to absorb thermal energy from a non-freeze liquid circulating through the heat pump, which non-freeze liquid can be used as a heat transfer liquid, and the heat pump is configured to transfer thermal energy to water flowing through the heat pump, - that non-freeze liquid can circulate in said heat transfer fluid pipeline system, wherein the heat exchanger device is configured such that non-freeze liquid is conveyed through the heat exchanger device, wherein the non-freeze liquid can absorb thermal energy from waste water in the collector tank, wherein the heat exchanger device further comprises one or more sets comprising each a plurality of heat exchanger elements within the wastewater of the collector tank, each heat exchanger element comprising at least two substantially parallel plates (71,72) which are arranged essentially parallel to each other such that they substantially overlap, characterized in that the system comprises, a preparatory unit and a cutting pump, wherein the cutting pump is located in the preparatory unit to pump waste water from the preparatory unit to the collector tank or to a buffer tank connected to the collector tank, and in that the at least two substantially parallel plates (71, 72) are of a self-supporting polymeric material, wherein a non-freeze liquid inlet is disposed at one end of each, heat exchanger element and an outlet for non-freeze liquid is provided at the other end of each heat exchanger element, wherein between the two plates (71, 72) and the inlet and the outlet is defined an internal flow passage for the non-freeze liquid which internal flow passage extends over substantially the entire surface the two parallel plates (71, 72) represent allowing the non-freeze liquid to circulate throughout the heat exchanger element in a flow direction from the inlet to the outlet. - a collector tank - a supply pipeline system (10; 110, 126; 210, 210a; 210, 210b, 226) for supplying waste water to the collector tank - a heat pump, - a heat exchanger device arranged in the collector tank and which is in contact with said waste water, - a heat transfer fluid pipeline system arranged between the heat pump and the heat exchanger device, - the heat pump is configured to absorb thermal energy from a non-freeze liquid circulating through the heat pump, which non-freeze liquid can be used as a heat transfer liquid, and the heat pump is configured to transfer thermal energy to water flowing through the heat pump, - that non-freeze liquid can circulate in said heat transfer fluid pipeline system, wherein the heat exchanger device is configured such that non-freeze liquid is conveyed through the heat exchanger device, wherein the non-freeze liquid can absorb thermal energy from waste water in the collector tank, wherein the heat exchanger device further comprises one or more sets comprising each a plurality of heat exchanger elements within the wastewater of the collector tank, each heat exchanger element comprising at least two substantially parallel plates (71,72) which are arranged essentially parallel to each other such that they substantially overlap, a preparatory unit and a cutting pump, wherein the cutting pump is located in the preparatory unit to pump waste water from the preparatory unit to the collector tank or to a buffer tank connected to the collector tank, and in that the at least two substantially parallel plates (71, 72) are of a self-supporting polymeric material, wherein a non-freeze liquid inlet is disposed at one end of each, heat exchanger element and an outlet for non-freeze liquid is provided at the other end of each heat exchanger element, wherein between the two plates (71, 72) and the inlet and the outlet is defined an internal flow passage for the non-freeze liquid which internal flow passage extends over substantially the entire surface the two parallel plates (71, 72) represent allowing the non-freeze liquid to circulate throughout the heat exchanger element in a flow direction from the inlet to the outlet.