Grey Water Heat Recovery

Grey Water Heat Recovery

Grey water is water from the bath tub, shower, sink and washing machine. It accumulates continuously and is warm, approximately 30 degrees Celsius. Every day a considerable amount of energy disappears with the grey water into the sewer system. A grey water heat recovery system uses the energy contained in the greywater.

Operating principle of a greywater heat recovery system

Greywater_Recycling_Heat_Recovery_System_1To run a grey water heat recovery system, the grey water must be collected separately. A grey water heat recovery system consists of a heat exchanger with a self-cleaning filter installed upstream that collects coarse particles of dirt and feeds them into the sewage system at regular intervals. Inside the heat exchanger, the grey water releases up to 60% of its energy into the counter flow of cold water, which is heated in the process and then be fed into a hot water tank.


Cost effectiveness of a grey water heat recovery system

Grey water heat recovery is of particular interest in multi-family homes, where the investment costs amortize more quickly due to the high volume of grey water.  Up to 15 kWh of energy can be recycled from one cubic metre of grey water, which equals savings of approximately 50% of the heating energy required for hot water. The yield of a grey water heat recovery system is approximately equal to that of a thermal solar system.