Water heat recycling is the use of a heat exchanger to transfer heat from waste water to incoming cold water, reducing the amount of energy necessary to heat that water for use. This will cut down on energy usage in a building, reducing operating costs and lowering the size of the environmental footprint. Systems vary in design and cost and are often available through contractors who specialize in environmentally friendly retrofits and installation of new energy conservation systems.
In the process of running showers, washing dishes, and performing other tasks with hot water, hot water pours down the drain and the energy expended to heat it is effectively wasted, as the water dumps into a drainage system and disappears. With water heat recycling, the water moves through a heat exchanger that wraps around an incoming cold water pipe, heating cold water as it enters a structure. The preheated water takes less time to bring up to the needed temperature, cutting down on overall energy use.
Many systems come with a storage tank. Without the tank, the only time heat exchange could take place would be when hot water is leaving a building and cold water is coming in. Homes can add additional efficiency to their water heat recycling system by connecting it to a gray-water recycler, recovering water that may be usable for irrigation, flushing toilets, and similar activities. This will reduce overall water usage and limit the demand for freshwater.
It is possible to install a water heat recycling system in an existing structure, often leaving most of the current plumbing intact. In some regions, grants are available to help homes increase energy efficiency, and it may be possible to get financial assistance if the cost of a system is too high. Tax benefits may also be available, depending on the system and the tax year. In new design, architects can build a water heat recycling plan into the structure, installing it from the start.
Maintaining such systems is relatively simple, as they rely on plumbing that already needs to be in place; homes need pipes to carry away waste water, for example, and a brief diversion to a heat exchanger does not constitute a major change. The system is also easy for any plumber to work on. No special environmental certifications are required to make repairs or retrofits to the water heat recycling system, as it relies on basic plumbing principles.