Waiting for hot water is a common reason for large water bills. In fact, according to a Department of Energy study, an average family of four wastes up to 14,000 gallons of water each year waiting for hot water. Nationally, water conservation has become so important that many states and municipalities are routinely imposing water bans or offering rebates.
A hot water recirculating system is a continuous loop of slow-moving warm water that constantly circulates water through the pipes from the hot water heater to the most distant fixture. The water is always hot in the pipes and no water is wasted during the wait when a fixture is used. As water begins to cool in the hot water line, the recirculating pump will move the hot water from the heater throughout the pipe back to the hot water heater, creating a continual movement of water instantly available for use.
A hot water recirculating system uses a dedicated return line from the point of use located most distant from the hot water tank back to the hot water tank. In an existing home where this return line was not installed a crossover type system can be used as a retrofit where the cold water line is used as a return line with a temperature control device closing the connection between the hot and cold lines at a set temperature. Using the cold water line as a return has the disadvantage of potentially heating the contained water in the cold water pipe. However, in new homes, we install a loop of hot water so there is always a dedicated return and the system will not encounter problems.
A frequently asked question is, “What about the energy used by the pump and the cooling of the hot water in the loop?” This is a good question! There is a trade-off as the cost of energy is typically less than the cost of the expense of wasted water.