A better heat pump water heater?

[marx290]

dhaslam, I hear what you're saying with freezing pipes. I don't really have that problem here, but I can see how warm wastewater could be needed.

I haven't messed with the evacuated tubes yet, but I've heard great things! I'd prefer the passive method over one which consumes electricity, but in certain situations, cooling is needed anyway, so you know...birds...stones...awful phrase. :-P

I'm planning on eventually heating water as a byproduct of power generation, but I still enjoy the subject of heat pumps, and I think there are practical ways to improve them.

Ctgottapee, I guess I wasn't specific enough; I am talking about pumping heat out of waste water, not passively preheating water before it goes to a water heater. Yes, the long copper heat exchangers are not practical for all situations. What I was thinking of was a heat exchanger tank, with either immersed coils, or evaporator coils wrapped around the outside of the metal tank. A clean out port would be necessary to spray it out a bit. Of course, you wouldn't want any blackwater going in there!