Benjamin Dinkel

Hey John,
It’s exciting you’re starting the design process for your rocket mass heater.

To 1:
The dimensions sound about right. 30cm is not very deep. Since you have a lot of height in your workshop, why not go a bit higher?

The gap between barrel and riser can easily be a bit bigger. I would aim for 10cm.


To 2:
You could follow your local code as a reference. Just think of the barrel as a exhaust pipe and of your wall as flammable.
I would go for at least 40 cm, but that’s more feeling than knowing.
Where would you put the brick shield? Against the wall? Against the barrel?

To 3:
If I understand correctly, that’s the preferred way. Because you’ll have the barrel “kiss” the exhaust. You will just need to make everything ample enough for good flow.

Could you provide a little sketch for your design? That makes your questions much easier to answer with accuracy.

I find almost all RMH to be beautiful.
Including the ones I made recently:


Mediterranean lightweight 6" J-tube



8" J Tube with half barrel bench

Thanks Thomas.
It was super fun to build and performs well so far.

I was surprised to see the barrel still warm the next morning after a 45 min fire. I'm assuming it's the full fire brick heat riser that stores a lot of heat and slowly gives it off to the top of the barrel.

This is what the heater looks like now, almost completely dried, before painting.



The clients will wait for it to completely dry and then paint it in a blue, I also like the white.
The colors of the barrel are very pretty to me.

thomas rubino wrote:Oh, it would be nice to share it with the neighbors, but selling to the power company is a losing proposition.

It often is, but depends on where you are. Here (in Spain) there's contracts in which you use the grid as a virtual battery. You only pay them for what you take more than what you've given them. Which to me is a pretty sweet deal.
Unfortunately I'm 100 meters from the next connection point and a neighbor got a quote for around 10k euros to get connected...

Hey M,

first of all congratulations on your purchase. And for thinking outside the septic tank concept!
You're right. With a composting toilet and a working grey water system the septic tank is not necessary. And the saved trees might benefit from water and nutrients.

I really hope you'll encounter a designer/engineer for your system.
Are there no companies that specialize in grey water use around? In Europe I could come up with at least a couple of leads.

Matt, I can understand the direction you're going. But if you design it the right way (with a potential septic tank that get's added later on by the new owners or you before selling) I don't see the problem.

Or my favorite:
Get grid access and give it to your neighbors, be that for free or even selling it to the grid!

Heat some water for taking a bath

Pre-Heat the thermal mass of your house (in winter)

Run a dehumidifier (if you have moisture problems)

Run an electric food dehydrator

Day 9 (of continuos work) was a bit of a frenzy.
We applied a coat of clay and lime plaster with a mesh.




And then a last layer of lime plaster with whitish sand and rubbed it all into its final form.




Now the clients need to patiently wait for the plaster to dry before giving it all a coat of silicate paint

Day 8 we just did some minor touch ups and built a wooden structure for the sofa cushions.
We had a fire in the morning and evening to speed up the drying.
And the barrel stayed warm all day. And it started easily.

Tomorrow we'll plaster everything