How hillbilly can it be?
I saw one in an off grid commercial bakery... and the health inspector passed it as suitable.
It was a normal tall 40G gas water heater, with a couple tweaks.
Mostly, the burner was removed, the opening made larger, and the bottom reinforced (think cast iron skillet).
Probably a better than standard chimney pipe? Not sure what they did about the gap between the top of the heater and the pipe.
Seems like he made a sheet metal door for it, but I don't recall it having any input draft control. Might have had a flue damper?
A few handfuls of short sawmill cutoffs, like 1x1 ~1x2 maybe 6" long in the skillet.
It did not take long at all for the 40G to get to whatever temp at the faucet the inspector wanted it. He checked it with a thermometer at the faucet, after maybe a 30' run of uninsulated 1/2" CU pipe from the heater. He was amazed. I was stunned.
I tried to get photo of it a few years ago, but the baker retired and the place is mostly used like a storage shed now.
Can make a lot of hot water with not much wood.
Could do something similar but different.
These are cool, but cast iron and heavy to ship from central OH or eastern PA.
Fire in a small area in the center, completely surrounded by a pretty high capacity water jacket.
It thermosiphons to a 40G storage tank, and maybe 10~15 minutes after the fire is started, the water is more than plenty hot enough to shower comfortably.
Locally they make about the same thing, on its side, from SS.
G-
