Automatically Preheat Water to Save Energy

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Usually when we are talking about plumbing fixtures for green building we are dealing with something that conserves water. But some plumbing devices can contribute to energy savings, as well.

When you are in the shower, the hot water from the shower strikes your body and transfers some heat before it falls away. But most of the heat in that water simply goes down the drain. Reportedly, 80 to 90 percent of the energy used to heat water for the shower is lost down the drain.

A drain water heat recovery unit (DWHR) transfers heat from water running down the drain to cold water going to the water heater. This preheats the water so that the heater is starting with warmer water, and thus needs less energy. A DWHR unit can save as much as 25-30% of the energy used for water heating, and payback periods range from 3 to 7 years, depending on use patterns.

Written by Philip Proefrock