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How it works

Learn how sewer heat recovery is a sustainable technology for King County.

Warm and hot wastewater flushed from homes and businesses is a significant energy source. The U.S. Department of Energy estimates that 350 billion kilowatt-hours of heat energy are flushed down the drains in the United States every year—roughly enough to power 30 million homes.

Through this technology, a portion of wastewater is captured in an underground holding tank where its heat energy is transferred in a heat exchanger, which allows a heat pump to extract that energy and transport it to a connected building's domestic hot water or heating or cooling system.

Repurposing this otherwise wasted heat energy resource is another way building owners can meet sustainability goals and positively contribute to climate action.

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Did you know?

Independent studies have shown the energy value of Sewer Heat Recovery technology.

NOTE: The attached is a third-party, independent report. Data and conclusions are those of the author.

how sewer heat recovery works: Waste starts in sewer, into a holding tank and pump, then a heat exchanger, then it moves to a heat pump then hot water to a connected building.

Illustration of process is an example. Technology requirements will vary.

Sewer heat recovery is a sustainable energy solution that reduces onsite fossil fuel combustion, lowers carbon emissions, and decreases a building’s carbon footprint in facilities that use hydronic (circulating water) systems for heating or cooling and/or facilities with significant domestic hot water requirements, such as schools, gyms, or commercial kitchens.

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