Thanks for sharing this. I have a heat exchanger collection for my energy projects hobby.
I’ve considered a heat recovery on a drain but it was pretty low on the priority list. I would consider it if I was going for a zero
carbon house design. And if I had extra cash or could make my own even better. Personally I would simply buy a extra
solar panel and add it to my renewable energy system and insulate the heck out of my house and
water heaters, etc. As I don’t buy much power but harvest sunlight I don’t pay extra for hot water. But if I did buy I might be more motivated.
Those heat exchangers are not very efficient. I like the flattened pipes and countercurrent flow on this one. I would be concerned about scale, slime, dirt reducing the heat transfer in the waste pipe. Also I don’t take lots of showers or long showers and in general use very little water. So it would not pay for itself.
We have been recommending folks simplify and produce more electricity by installing a better solar energy system with more panels. We have stopped building tracking solar panel arrays, solar thermal domestic hot water systems, and heat recovery systems because solar panels have become affordable and are reliable. We had too many problems with the other systems. However I’m considering a heat recovery ventilator on my Motorhome because I cannot figure out a way to insulate it better than I have which is still very poor. So as often is the case
the answer is “it depends”. if you like to take hour long showers everyday and buy power then the drain heat recovery might be worth the investment. .
If you want a simplified solar energy system with no batteries there’s a electronic gizmo that diverts the solar energy directly to your water heater whenever it turns on rather than buying from the grid. Off
course this wouldn’t work at night.