The Metlund D'MAND System rapidly moves the ambient temperature water in the existing lines. In a tankless water heater system, this allows the water heater to work less bringing hot water to the fixture because colder city water is not coming into the water heater at this time. The Metlund D'MAND System is simply moving the interior water in the home supply line back to the water heater.
Once a tap is opened, the outside water is drawn through the heater to supply hot water to the fixture. The Delta-T (rise of temperature) can be set to a lower "set" point, thus using less energy to supply the hot water before you turn the tap on.
At the push of a button, the Metlund® Hot Water D'MAND® System circulates the ambient temperature water in the hot water pipes (water that is normally lost down the drain) back to the water heater. This occurs up to 80% faster than just letting the water run down the drain - the usual scenario. Depending on the plumbing layout, the route and time can vary. The Metlund D'MAND System moves the water so rapidly, that hot water arrives at the fixtures before the heat is lost through the pipe.
As the ambient temperature water in the cold water line travels towards the hot water heater, the D'MAND System fills the hot water line with hot water. When the hot water reaches the D'MAND System, a thermal sensor (thermistor) senses a temperature rise and quickly closes the zone valve while it shuts the pump off. The sophisticated electronic circuitry that does this is attached to the high-performance pump housing.
This results in getting hot water to the fixtures four to five times quicker (on average), greater convenience in not having to wait, a savings in water and energy, and a reduction in sewage costs. As a by-product of these savings, a cumulative result is the improvement of air quality.
The Metlund D'MAND System can utilize the cold water line as a return line or use a dedicated return line. By using the existing cold water line, it is easy to retrofit existing homes or businesses. Special plumbing is not needed, and since the System will not allow for hot water to cross over to the cold water line, all the cold water fixtures still have cold water.