Hope that was fun for you to write because it in no way addresses my question. I wasn't asking what you thought of the heat exchanger or how I live. Clearly you have little understanding of the unit, as the supply water and the grey water do not come in any closer contact than in any other house plumbed to code, each contained in their own system, divided by a double wall. So don't worry, I'm not breaking any codes but thanks for ALL your concern.Wow.
Hardly “free heat” if you have to spend a lot of money trying to engineer a system to work for you. Seriously? Tiny house? Undersized water heater? Undersized electric service? -30 F temperatures? AND you want nice hot showers as if you lived in a normal sized house in a slightly different climate without all your limitations?
I’m sure there is some code about gray-water heat exchangers and implementing them safely. Even if you live off the grid in some unincorporated mountain area, following some code standards makes sense even if not required or inspected.
If a commercially manufactured unit can’t work for you regardless of the reasons, give up the science project.
Spending money is exactly what I'm avoiding by not buying the commercial product, I'm getting copper cut offs from local plumbers so yes it's basically free. And I've found it to be an interesting "science project" so I'm not bothered about spending my time on it.
Hope you've enjoyed participating in this thread because your 2c is absolutely worthless to me.