For many older homes built before the advent of hot water recirculation systems, lag times while we wait for hot water to come out of a faucet is something many of us deal with in our homes every day. This not only wastes our time, but it also wastes energy and a lot of water, 6+ gallons of water a day on average per household. This equals 700M gallons a day, nationwide, dumped down the drain because the water was not hot enough for its application.
With traditional recirculation systems, hot water is looped back to the hot water source via an additional pipe that is installed during construction. This pipe allows the hot water to continually flow through a looped system powered by a pump, thus providing instant hot water to any location on that plumbing line. Plumbing for this type of system as a retrofit application is almost always price prohibitive and impractical given the evasiveness of having to install a return line through existing conditions and finishes.
On the market now are several retrofit recirculation systems that through the use of valves, pass the “cooled” water in the hot water supply line back to the cold water supply line and once the desired temperature is achieved a sensor then directs the hot water back to the faucet. This is achieved by installing a pump at the plumbing fixture furthest from the hot water source. From here a bypass valve directs any cooled water from the hot water supply line back to the cold water supply line. At a set temperature, a sensor then directs the hot water back to the faucet. This leaves the hot water supply line primed with hot water and any fixture along that plumbing line has access to instant hot water.
There are two ways to activate the system, either manually, or with a remote sensor. With a manual system, a user would activate the pump via a switch at any plumbing location. Let’s say in a three story home a retrofit recirculation pump is installed on the third floor. When hot water is desired anywhere along that plumbing line a user would simply press a switch that would activate the pump on the third floor, priming the hot water supply line to the desired temperature. With remote sensor switching, the system is activated via motion sensors, automatically priming the hot water supply line whether or not the system is used or not. This uses more energy than the manual switching but the system is only activated when a user is in proximity to a plumbing fixture. In contrast to a non-retrofit system which continually circulates water 24 hours a day, the energy use of a remote sensor retrofit system is only a small fraction of the foremost.
There are several manufactures producing on demand retrofit pumps, generally ranging from $400-600 in cost. The systems are also quite easy to install, with only a few required tools and some Teflon tape, almost anyone can install one of these systems.