Keeping hot water in the pipes at all times available for use can increase your water heating costs. There are a number of steps you can take which can cut the costs of operating a recirculation system and still provide the convenience and water saving benefits of hot water recirculation. The system can be operated by a programmable timer to only turn on at that time of day and days when you typically are using water and shutting off while you are sleeping or, at work. You can also use switches that will operate the recirculation system for a set length of time after a switch is pressed allowing manual operation of the system by just pressing the button a little while before you intend to use hot water. A method that is rapidly gaining popularity is the use of occupancy sensors, which automatically activate the system when people are in the rooms with fixtures served by the recirculation system. Using recirculation on a hot water distribution system does not have to waste a lot of energy to provide instant hot water.
Dedicated Return Line Systems
When a dedicated return line is used the system is comprised of a pipe looping back from the hot water line at the furthest point(s) to either the cold line feeding the water heater or, into the water heater drain connection. A circulator pump is used to pump the water through the loop and a check valve is used to prevent cold water from back feeding through the return line. There is also a valve that is used to throttle the flow in the return line to check the velocity of the water flowing in the loop and prevent erosion of the pipes by excessive flow rates of the water in the pipes. The circulator pump should be constructed from materials, which resist corrosion as the pumps typically used for hot water heating systems typically use cast iron impellers and housings, which will corrode in an open system. Sometimes a plumber may be able to run the pipes in a manner where the recirculation will occur by gravity without the use of a pump. This dedicated return line type system can be installed in new construction and in homes where the return lines can be run without major difficulty.
Cold Water Line Return Recirculation Systems
There are also numerous recirculation systems, which do not require the use of a dedicated return line. These systems are ideal for use in homes where it would be difficult and expensive to run a dedicated return line to the water heater. Many of these systems use a thermostatic valve and pump connecting between the hot and cold angle stop valves under a lavatory sink vanity. Whenever the hot water cools off to the set temperature, the system activates and pumps the cooled off hot water into the cold water supply line until hot water again reaches the fixture. The cooled of hot water is not hot enough to present a problem on the cold side and it rapidly cools off to the ambient temperature. The only down side is if you were wanting to get “cold” water you would have to wait for it to arrive which is quite typical anyway. Many manufacturers such as Grundfos, Watts, Laing, RedyTemp, and Metlund manufacture systems, which can be installed utilizing cold water supply lines for recirculation. With these systems you can easily have hot water waiting for you to use every time and stop pouring gallons of water down the drain waiting for hot water to arrive.