UBC Graduate Research

Drain water heat recovery : a review of performance, economics, practical issues and applications Frankowski, Chris


This project evaluates the economics of Drain Water Heat Recovery (DWHR), more specifically the performance of a horizontal DWHR device manufactured by EcoDrain, the A1000. The device was tested in a rig that mimics a typical real world installation. The temperature increase and flow rate of fresh water passing through the device was recorded to determine the energy saved while showering. Both the transient and steady state performance of the device was determined. By combining the testing results with a dataset of Canadian household sizes, showering habits, and energy costs, a recommendation is made for the conditions under which the installation of an EcoDrain would be economically advantageous. The testing simulates an installation where the fresh water being preheated supplies only the associated fixture, which would be the easiest installation for an existing building. Testing showed an average temperature increase of 12.2°C with a flow rate of 3.87 L/min of fresh water passing through the DWHR device, which corresponds to a heat transfer rate (power savings) of 3.29 kW, and a total of 0.43 kWh saved per shower. The average Canadian household has a size of 2.59 people, with each person showering once a day for 8.5 minutes each. Energy costs vary significantly around the country, but the average electricity rate is 9.41¢/kWh and 7.13 $/GJ. For the average household, the NPV of DWHR is -$203.68 for homes with electric water heaters and -$464.88 for homes with natural gas water heaters. DWHR is much more economical for households with electric hot water heaters as their energy costs are much higher. A household of 4 or more people with an electric hot water heater would benefit from installing a DWHR device such as the EcoDrain. Locations with natural gas heaters would benefit from DWHR if there are more than 14 users a day, or if natural gas prices return to more historic levels. Disclaimer: “UBC SEEDS provides students with the opportunity to share the findings of their studies, as well as their opinions, conclusions and recommendations with the UBC community. The reader should bear in mind that this is a student project/report and is not an official document of UBC. Furthermore readers should bear in mind that these reports may not reflect the current status of activities at UBC. We urge you to contact the research persons mentioned in a report or the SEEDS Coordinator about the current status of the subject matter of a project/report.”

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Attribution-NonCommercial-NoDerivs 2.5 Canada