What is Drain Water Heat Recovery


In residential or multi-residential applications, when warm water goes down your drain from showering, a faucet, or washing appliances, it carries away valuable energy with it. The same applies for commercial or industrial applications, with any heated water processes which carry away valuable energy as they run down a drain.

Drain water heat recovery (DWHR) is the process of recovering part of this valuable energy from the warm water, and using it to preheat your incoming cold fresh water. This process can be used for your home, apartment, condo, business or many industrial processes using heated water.

This simple innovative and proven technology has no moving parts, is already in-use around the world, providing affordable long-lasting savings results.


Utilizing the Falling Film Heat Exchange Process


    In general, as water flows down a vertical drain pipe it will flow rather fast. Most people believe there is not enough time for the heat transfer to occur between the warm liquid and the wall of the inner pipe. The fact is that heat transfer is not highly dependent upon resident time but is far more dependent upon intimate contact between the fluid and the wall. As the drain water speeds up it becomes a very thin turbulent film of about a millimeter in thickness. As a result, it imparts its heat to the pipe wall very readily.

In the case of the patented Power-Pipe® DWHR, a series of formed copper coils are tightly wrapped around a specific length of copper drainpipe at our manufacturing facility.

This process forms what is commonly known as a double wall heat exchanger. The double copper wall design protects incoming fresh cold water carried in the coils, from any possible chance of contamination with the out-flowing warm waste drain water.

Once a Power-Pipe® DWHR system is installed into a section of the drain stack, any time warm water from the water heating system is used and then runs down the drain, this warm waste water transfers its heat through the copper wall of the drain stack to the walls of the outside wrapped copper coils carrying the incoming cold fresh water.  The incoming cold fresh water is then preheated before it goes into the water heating system - no matter what type of water heating systems is being used.

With residential applications, it’s not uncommon to experience a 25F°  increase to incoming fresh water, prior to entering the water heater when using a Power-Pipe® DWHR system.

In commercial or industrial application, the energy savings and temperature change can be even more dramatic depending on the use and specifics of the application.

It’s that simple – yet highly effective.





Click the links below to learn more about Power Pipe and its applications.