May 22, 2013
Resource Efficiency

A drain water heat recovery (DWHR) unit is a simple, low-cost device which can reduce the energy used to heat water by up to 40%. Recently, Greening Homes has been able to provide free DWHR systems to our clients completing substantial renovations through a program offered by Enbridge. The DWHR system consists of a large copper pipe, between 4″ and 6″ tall, that replaces a vertical section of the main plumbing stack. Coiled around the large copper pipe are smaller copper pipes. Cold water enters these small pipes and is heated by warm waste water coming down the larger pipe. The pre-heated water is then routed to the water heater. The energy, instead of going down the drain, is now returning to the water heater to be used again.

In our latest DWHR installation, we attached temperature gauges to the incoming and outgoing water lines to monitor the effectiveness of this technology. The results proved the manufacturer”s claims to be true! With someone taking a hot shower,  we measured the incoming water temperature at 9C; and after running through the DWHR system, it had been heated to 24C. This translates to a peak recovery rate of approximately 9.9kW – almost equal to the output of the water heater itself!