Glenn Herbert

Lots of excellent advice here!

I would say about the air gap under the RMH, that it may well be superfluous for the mass bench away from the core, especially if there is a good amount of material below the duct or bell. Under the combustion core, I would always make an air gap. A 6" J-tube in a moderate climate where it will not be run for many hours on end would likely be fine with a small gap, while a batch box or an 8" J-tube in a cold climate would want large gaps and multiple layers of insulation.

Mounting the core beneath the IBC would definitely require water-shedding or diverting treatment. Positive drainage so that water cannot accumulate near the core, and construction separated from the earth so damp soil cannot touch it, would be needed. I would want a large enough space that you could reach and look in when it is not running to check for leaks or other issues. I would put the bell in a corner of the IBC which I think would give the most spacious feel; this would make the underside pretty easy to get at for inspection. I think the initial construction/installation of the flange in the floor would be no different than in the wall. Maybe caulk would be easier to keep in place during installation.

If you exit with a duct from the base of the bell and run all around the sides of the IBC, the chimney could rise right next to the bell and have a bypass connecting the top of the bell to the chimney. Gradually closing the bypass should be able to encourage flow through the duct.

Our ram was fed from a 3/4" HDPE pipe about 100' long and about 20-25' head. The whole pump weighed less than 40 pounds, I would say, and was about a foot or so high. It ran on probably less than 2 gpm, maybe 1 gpm.

Looking at images online, manzanita seems extremely small and twisty. You can certainly build with it, but would probably be best off gravitating to more organic forms rather than rectilinear ones. It might be well suited to "wattle and daub" construction, which is essentially a semi-woven frame of small sticks and laths with cob plastered over it on both sides, interlocking to make a sturdy wall. This would require good weather protection, foundation walls high enough that snow or rain don't splash off the ground and wet the base of the wall, and an overhanging roof that keeps direct rain off the rest (known as a "good hat and boots".)

What sort of house do you want, and how large? That will influence how suitable manzanita is for your project too.

What is the growth habit of your manzanitas? How straight can you get logs, and how large? A photo of some growing (with something for scale) would be helpful for those of us who do not have access to it.

The type of framing you would do depends on the answers to these questions. Small or crooked timber would suggest a more close-studded frame while large straight timbers could be used as traditional timber framing with large infill panels. Your climate and other available local resources are also important.

Back in the early 1970s, my father installed a ram pump on the outflow of our spring to deliver water to the house about 600' away and 10' higher than the spring. It was small, considerably smaller than the ones I have seen on the websites linked from this thread, but worked fine for a family's water supply. Except, of course, when the plunger valve stuck in the open position in the middle of winter and we had to walk 600' through the snow and across a ravine to unstick it in the morning so we could wash up before school...

If your flow is small enough that you would need to collect it all, then a dam to collect it would not need to be large. It might need to be fairly massive to stand floods, depending on the characteristics of your situation. If you have no legal impediments to putting something in the watercourse, the practical issues should be relatively minor.

If you want the heater in the tub and fed through the side, I see no reason to run the exhaust out the side of the tub rather than straight up. Straight up, perhaps insulated, offers the least amount of drag on airflow, and would allow for a startup bypass between top of riser and chimney. Then once the fire is going well, closing the bypass routes the flow down through whatever bell or duct you decide on.

I would locate the riser enclosure (propane tank(s)) as close to the tote wall as possible while leaving some water space for safety, so the feed tube can be as vertical as possible, and allow a bit of flat burn tunnel. I think this will help the combustion effectiveness. For that matter, you could even make a larger (say 12" w x 20" h) metal plate in the tote wall and have a proper J-tube, with all insulated vertical feed outside, burn tunnel through the flange, and riser in enclosure a couple of inches inside the tote. Dimensions like 12" feed, 18" burn tunnel, and 36" riser (measured along outer edges of flow channel) would probably work very well.

Another idea would be to mount a "bell" into the floor of the tote and put the insulated J-tube under that, so the hot core doesn't need to pass through the tote wall at all. Run the chimney from near the base of the bell, either straight up or around the floor first and then up. Elevating the tote by a foot, or digging down a foot for the core, seem like trivial tasks.

If you are not going to open the stone wall to the leanto, just putting the RMH next to that will be good. Without trying to heat the leanto, making that stone mass warmish will be positive all winter. I think you will be better off warming the shared wall than an exterior wall. Two meters is plenty of height for RMH clearances, so you don't need to worry about that. Depending on the details, you may want a heat shield on the ceiling above it.

It looks like your brick extension is a few steps down from the original stone structure. What is the wall between them like? Mostly solid, or any major open space? How thick? Building your RMH in/on/against that wall would probably be your best bet. How thick is the stone wall there? You would benefit from mass, but mass that is more than a foot thick will take days to heat through. This would be fine for deep-winter climates which need heat continuously for weeks on end, but not for a place that needs warmth intermittently. The less constant the heating demand, the thinner your mass wants to be so it can be responsive within a few hours at most.