Stop in for a cup of coffee

WV64Signet said

Oh yeah..

I think they're trying to get those banned.

Too complex a system for me. Aren't some of those also the hot water source for the house?

Click to expand...

There is a heat exchanger for water that enters the hot water tank. Pre-heats.
Building code now requires a heat exchanger on the shower drain to preheat the water that goes into hot water tank.