Rocket Stove for Heating Bathing water Pot

Hi
We have a 90 Liter Copper water pot - that we want to use to heat water for Bathing - using RMH design. See our sketch based on research we have done. Once we receive the comments - and if positive - we can finalise the dimensions and post the same here.

The exhaust(I) should come from the bottom of the duct (H), thus only exhausting the coolest gasses.
Assuming (K) is bricks, I would want a minimal amount of such mass,enough to support the copper vessel(G).
It will suck up heat that could be going into the water.
I would replace masonry with insulation where I could,especially on the top side of the heater.
Speaking of G, a copper tank seems awfully nice to cover up in this.
I would use it elsewhere, like to broil wort,or sell it to pay for other materials.
Derelict gas or electric water heaters are usually available free or cheap.
Your rocket looks like a J, but the fuel feed is capped and the air is coming in seprate from the fuel.
This is not a known design to me.

Since you have no inlet for water, I would guess you are hauling it by hand.
The fill cap seems hard to get to.Would you have to climb a ladder  with a bucket of water?
Moving the tank and lower and exhausting the riser (E) into the side of the ducting(H),would make the whole thing lower.

One more thing, the tap would ideally have a intake that floated at the surface of the tank water in order to get the hottest water in the tank,but I don't know of good way to do that.

Being in India, utilities, economics and resources are likely different than we are used to in the US. I agree with many of William's comments, and have a few to add.

the freedom from power or technology dependence is a plus, as long as the convenience level is acceptable. I think the scale looks bigger than it is, and a ladder would not be needed for filling, maybe a step or two. If you plan on filling, heating, and draining the pot for each use, a pipe from the base is appropriate.

I realize this is a sketch and not exactly to scale, but the burn tunnel D is too long and the heat riser E is too short for good results. If the pot will be directly over the riser, you need more space for combustion to complete before hitting the pot and being cooled.

Brick for the shell and pot support is good, but the burn tunnel, riser and chamber around the pot need to be as insulating as possible. For low tech materials, I would suggest a thick layer of cob with lots of straw, rice hulls, or whatever will burn out and leave lots of tiny voids - a kind of clay sponge. I would move the pot supports out to the edges of the pot to allow the support to be independent of the riser and its insulation. I would make the chimney exit from the pot chamber from the bottom as William suggests, to allow heat to build up inside.


I agree that the J-tube feed is not best practice as shown - the top of the feed tube needs to be the only air inlet, or you will have fire climbing up the wood and causing a hazard. My and others' experience is that an ashpit is not needed, as there is little ash buildup and it can easily be cleaned by hand before each fire. A smooth floor gives good flame and coal combustion results.

Thank you William & Glenn for all the thoughts and suggestions. Am slowly absorbing them and will soon post a revised design - sketch based on them. That would also give me opportunity to see if I have understood your thoughts clearly. Thank you.

So here is my revised design (based on feedback of William & Glenn) - these are the changes:

Removed AshPit and side air-intake (B & C removed)
Lowered the exhaust chimney to bottom of the pot (I)
Added insulation of COB (L)
Heat riser is now partly the riser (E) and partly duct around the pot (H)
Move pot stand wedges to the outside edge of the pot (F)
Added dimensions in the sketch (not to scale)

Also considering doing away the masonry bricks totally and replace the whole structure with COB (ensuring the top of the whole system has a roof to save from rain)

Also need help with the material of the burn tunnel (D) and heat riser (E)
Are fire bricks better or should we choose metal pipe of 6" dia

Thanks in advance

I'd be concerned about the copper being corroded by direct exposure to the exhaust gases. Here's a link with resistances of copper to various chemicals: corrosion resistance doc

In particular, copper is not resistant to carbonic acid, which is formed when carbon dioxide dissolves in water (think about the condensation when starting up/shutting down the burn).

Would love an update on this.

If you want more suggestions, I agree with Jason, Erica and Ernie don't recommend using metal around very hot gasses.  Fire bricks for the riser and ceramic fiberboard if available for the burn tunnel are what they recommend.  I'm not an expert, I hope Glenn or William or Big Al will chime in.