Hot water is typically the second-largest use of energy in a home (after space heating and cooling). Despite its resource intensity, the hot-water-delivery system is seldom an area of focus when constructing a home. As a result, many homes have systems that take minutes to deliver hot water to the faucet and waste large amounts of energy and water in the process. Approximately 10-15 percent of energy use associated with hot water is wasted in distribution losses.
A brief article appeared in The Santa Barbara Independent a few months back promoting hot-water-recirculating systems as a way to save water. A recirculating system is a hot-water line that loops throughout the house, connecting to all the fixtures that use hot water before returning to the water heater. These systems usually have a timer that runs a pump during fixed periods of peak hot-water usage. By continuously circulating hot water during peak periods, it provides instant hot water and saves water by eliminating the water that typically runs down the drain while waiting for hot water to arrive.
Water is saved using this system but only by using an excessive amount of extra energy. Another drawback: The pipes tend to fail prematurely (usually in five to six years) by corrosion from the continuous flow velocity of the water and from the water chemistry — certainly an issue in Santa Barbara with our hard water.