WHAT IS DRAIN WATER HEAT RECOVERY?
A residential drain water heat recovery device consists of a copper potable water tube wound around a central copper drain tube.
The drain water heat recovery unit replaces a section of your vertical drain stack where warm water from the shower usually drains.
Wastewater from your shower or other sources of heated water heats the inner copper drain tube of the drain water heat recovery unit as it flows down the drain. At the same time, cold water is flowing in the outer copper potable water tube that is wound around this central drain tube. The outer coil is trying to cool down the warm central drain pipe and the result is that a heat exchange takes place. The cold water in the coil extracts the heat energy from the drain pipe and is heated using waste energy.
The preheated water in the coil feeds the water heater and/or the cold side of the shower. Two things occur;
At the shower, you are now mixing warm water from the drain water heat recovery unit with hot water resulting in the use of less hot water in the shower to achieve the desired shower temperature.
Instead of feeding cold water to the water heater, you are now feeding it warm water. For tankless hot water heaters, this means a significant increase in the flow rate of hot water. For tank hot water heaters this means up to 3x more hot water for showering. The overall saving is up to 40% on the cost of heating water