Rocket Stoves

Photographs of Ernie Wisner's Water Heater

From the Don't Try this at Home department comes Ernie Wisner's photos of his experience building a rocket stove-charged water heater. This is a system based on such a good idea, but not one without its hazards. It is an idea everybody comes up with after thinking about the way rocket stoves work. To jump from the furniture as thermal battery concept to the water as thermal battery concept is a common route to take. But I have seen dear friends run hollering through the woods --naked as the day they were born-- from a highly pressurized very hot barrel. Plenty of water to put the fire out, but the water too hot to handle.

copper coil

What have you come up with for heating bathing water? We're interested in your woodfired hot tub stories as well, as that's another good idea. Ernie, the head cook and big bear in the woods at the North American School of Natural Building was determined to build a working shower at the Cob Castle, it's a castle afterall.

Copper pipe coiled inside a 15 gallon drum.

copper coil

Ernie's story: "Well I fired up the heater for the first time this build, it was delayed due to water leaks in the solder joints and after drying out it performed like a champ. I will do some timing to find out exactly how fast it heats a tank of water later; for now i was excited about the on-demand hot water. IT WORKS!!!!!!!!!!!!! yeehaw. it works really well so far but this is only the first firing and I want to put insulation around the outer barrel to see if I cant get it to work even better. I think we ought to stress that this is an experimental system (if someone sets it up wrong it will blow)."

brick chamber

20' soft copper pipe 1/2" diam
1 section triple walled stovepipe (30") 8" diam. and 10" diam. for heat riser
15 gal drum 27 1/2" tall
55 gal drum section 15" tall
27 bricks
50 gal electric hot water heater tank
a bunch of pipe and fittings
this is an experimental system so it was made to reconfigure easily and quickly so its got a bunch more plumbing than it really needs.

modified drum

Brick feed tube and sawed-off 55-gallon burn chamber.

feed hole and burn chamber

"I built this system because i like hot showers and hot running water in my kitchen. Oh and I don't like to wait forever to take a shower."

exhaust side

So I reasoned that I would need a few things built into a system to make it safe, practical, useful, and relatively easy to build. So I built a rocket stove hot water heater that heats water in a coil and thermo-siphons into a storage tank.

Background: standard water heater. Foreground, the heat riser sits on the brick chamber.

with heat riser

Well it does pretty darn good at heating 55 gallons of water in about 2 hours (you have to tend it and feed the rocket so it's not as spiffy as it sounds) and it didn't blow the coil with a steam lock, so I was pretty happy with the prototype.

with exhaust pipe

The second version of this water heater will be done with 3/4" copper tube due to steam formation in the 1/2".

shower rocket
This page was last modified on Tuesday, May 1, 2012.