Recycling heat from drainwater

We go to a lot of effort and expense to heat the water for our showers and baths, then let all that heat down the drain. What if there was a way to recycle the heat? It turns out there is. All you need is a simple heat exchanger that allows the hot drain water to preheat the cold water that flows into your hot water system or the cold tap of your shower. Unless your drain pipes are accessible, this may work best on new buildings or renovations.

A heat exchanger specifically designed for this purpose called the Power-Pipe is available from RenewABILITY, or in South Africa from Easy Energy.They say it can raise the incoming termperature from 10 to 25 degrees Celsius.

The incoming cold water passes through the copper pipes wrapped around the drain to absorb the waste heat.

Thanks to Treehugger where I picked up the idea (and the image).

These systems are called drain water heat recovery, and you can find more information by searching for that term by clicking this Google link.

Now what I would really like to see is heavy users of hot water like laundries, hair salons, gyms, using heat pump technology to actively pull the heat out of their waste water.