Joachim Brunson

Thanks Juila,

I think so too.
One way to make a good coil is to fill the the pipe with sand. That prevents buckling and flattening.

Also as far a Steve’s comments I still don’t see it... the rmh and water lines are open ended, there is no place for pressure to build. Heat will circulate the water through the boiler. With the lines switched the bottom of the tub will remain cold.

Thanks Steve!

This is true!
My intention was to use one-way-valves on the inlet and outlet. (The diagram was not intended to show pluming details) And to also include a drain at the lowest point and pressure valve at the highest point.  My question about your recommendation is: wouldn’t it be difficult to heat the tub to it’s depth if the hot is mostly at the top of the pool, being that heat rises?

Hello,

I’ve been working on this design for a rocket mass heater hot tub. This design is also boiler.  Attached are basic diagrams to show the concept not the actual build.   It seems to me that most of the designs i see are inefficient and sluff off too much heat and would require hours to heat up.
However I would like some feedback on any pros or cons to this concept.

We ran some numbers and suspect it would take about 45 min to heat 140 gal with this design.

One con being that it could get too hot.

Aslo im not sure if the coil above the fire would cause problems for the function of the mass heater.

Please let me know what you think.
Thanks!