Drain Water Heat Recovery

http://www.motherearthnews.com/diy/drain-water-heat-recovery.aspx

I've recently seen a few things about recovering the heat from drain water. The devices being promoted are supposed to recover heat that would normally go down the drain and use that energy to preheat cold water going into a water heater. The idea is that it will take less fuel to heat the water and thereby save energy.

I'm interested to know if any of our readers have firsthand experience with this. If so, please share your opinions in the comments section below.