Drain Water Heat Recovery: A field study of commercial applications

Drain water heat recovery (DWHR) as discussed in this report is the recovery of useful heat through a heat exchanger placed in the building drain system. This project was an effort to characterize the performance of drain water heat recovery systems as installed in commercial facilities. The concept was based on the observation that commercial occupancies can have hot water loads much larger than those in single family residences, and thus larger energy savings potential.​

We installed four DWHR systems for purposes of the project. The selected sites included an apartment building, a restaurant, a self-service laundry, and a student housing facility. The three systems that produced usable results recovered from 7.6 to 43 million Btu of useful energy annually, with a value of about $80 to $460 in natural gas savings.

This project was supported in part (or in whole) by a grant from the Minnesota Department of Commerce, Division of Energy Resources through the Conservation Applied Research and Development (CARD) program, which is funded by Minnesota ratepayers.