Thermosiphoning stove

Iam in process of building a wood stove water heater for my DIY cedar hottub   I’ve read a lot of different posts about them but no specifics on them so wondering what size pipe is best ? I have some 1” stainless steel tubing I was hoping to use. Is there an ideal elevation for the hot pipe in relation to the water level in the tub? Iam planing on running the pipe inside of the stove as opposed to wrapping it around. Does anyone have one of those Chofu stoves?thanks

I've investigated that too, though I haven't taken any action to actually building it yet.  I'd say 1" is the smallest diameter you'd want to use.  A couple of important points; you need a safety relief valve, I believe located at the top end of your circulation loop, vented to the outside.  You also need an air-purging valve, also located at the highest point of the system.  Most of the systems I've looked at have vertical rises in the range of at least 3-4'.

Have you looked at any manufactured ones?
I have and I will come back with what I have seen and some info I have gleened over the years.
The most important thing is to have an outlet at the bottom of the tub and the return inlet near the water level, and the intervening pipe must have nowhere where an air bubble can form.
IE it slopes evenly to the heat source, has horizontal coils in the heater each ring stepping upwards but not above the pipe outlet at the tub.
If you have vertical coils you will either allow pressure to build up, allow air bubbles to form and the thermosyphon effect will stop.
That is when it may blow up!
I dont believe an overpressure valve is needed, because the pipe should be short and open at both ends anyway.

Thanks for input guys. So few points; my coils have to be horizontally stacked as opposed to vertically with a gradual slope,1” smallest piping, 2” would be too big, only asking cause I can get some free? But my stove would have to be a lot bigger to have a coil of that inside it.