Greywater Heat Recovery

Figure 1. Schematic of drain water heat recovery

Figure 1. Schematic of drain water heat recovery

A number of drainwater heat recovery devices were assessed at CCHT in 2006. The purpose of this experiment is not only to assess the performance of the DWHR units but also to develop a standard test which would allow the manufacturers, utilities and governments to have reliable data to estimate energy savings.

The drain water heat recovery technology is simple in design and has proven effective in reducing the amount of energy needed to produce hot water. The units used in this study have similar designs which consist of 3 inch nominal (76.2mm) copper drain pipe wrapped with either half-inch nominal (12.7mm) or 3/8 inch nominal (9.5mm) soft copper tubing, where cold water is circulated recovering heat from the drain.

Figure 2.  Drain water heat recovery devices

Figure 2. Drain water heat recovery devices

The pipes obtained from the manufacturers are of various lengths and configurations but all have the same basic design. Eight different units were tested in this project. The experiments were performed using two different flow configurations, three different flow rates and three different shower temperatures in an effort to assess the performance and heat transfer rate of each unit in comparison with the others. The energy savings calculator that resulted from this evaluation can be found here:  Energy Savings Calculator


ARCHIVED - Turning drain water into wealth (PDF format, 252 KB)
Armstrong, M.M. Burrows, J.
Home Builder, 21 (6)
pp. 10. 2008-11-01

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