A new technology, "Hot Water on Demand," can save you money, water and energy. Old-fashioned conventional hot water recirculating systems use an electric pump at the water heater and require installation of an additional hot water pipe to circulate hot water back to the water heater from the opposite end of the home. With this system, hot water is almost instantaneous. The pump shuts off when water in the line is hot. As soon as it cools, the pump starts again, burning energy whether or not hot water is needed. Short of adding a second or third water heater, this has been the most cost-effective method of getting almost-instant hot water to all plumbing locations in the home while cutting down on wasted water.

Hot Water on Demand uses a thermostatically activated computer chip to control a series of electronic valves that move cooled water in the hot water line back to the water heater through the cold water line. Unlike the old method, water is not run down the drain it is kept in the system. Also, hot water is only pumped into the line when it is needed at the fixture, as opposed to the old system where water is pumped out of the water heater and into the system every time it cools down in the pipes.

Here's how it works: A pump with two control valves (one for hot water and one for cold water) and a small computerized control box (about the size of a coffee cup) are installed at the plumbing fixture farthest from the water heater. A low-voltage, bell-type wire is run from the computerized control box to a thermostatic sensor that clips on to the hot-water output pipe at the water heater. The system begins pumping cool water out of the hot water line and back to the water heater through the existing cold water line when the sensor at the water heater detects an increase in temperature of the water leaving the water heater. This increase in temperature occurs whenever hot water is turned on. Simply stated, the system is activated by turning hot water on for one or two seconds anywhere in the home. After a ten to twenty-second wait for the pump to do its job the faucet can be turned on again and hot water is available at the faucet a second or two after it is turned on the second time.

This is not a cheap home improvement. A do-it-yourself installation (including the computer-controlled pump system and other parts you will need) should cost about $550. Having the job done by a contractor might cost $1,000 or so.

This new technology was developed and patented by Metlund Resource Technology in Stockton, CA. Because of the patent, Metlund is the only company in the United States allowed to manufacture the new On Demand System for the next seventeen years.