I stumbled upon this thread while searching another topic. I love hot tubs!
At any rate, I don't know the status of this project as I don't visit the forums much any more but thought I'd share my experiences in case the project is still being considered....or for anyone interested. I have a 5'x3' cedar tub (~300 gallons) with the larger Snorkel underwater stove. Starting with a clean firebox (since ashes insulate), and filling it with very dry wrist to forearm sized pine....and keeping it fed, I can raise the water temp by 45° every hour. It takes a wheel barrow of wood to take the water from 55° to ~104°.....which, I'm guessing is ~40 pounds of wood.
The stove smokes until the fire is going good then, when it is kept going good, there is very little to no detectable smoke. The stove smokes terribly with less than totally dry wood...or with bigger pieces of wood...or hardwood that burns more slowly. Hence my reason for preferring pine or similarly soft wood. It burns fast
My tub has a cedar cover but it is not insulated nor is the tub itself. Even in freezing temps, the water loses less then 10° overnight. I can soak Fri night then, with only a small fire with several pieces of wood, can get it back up to temp Sat morning.
Re sanitation: I use 30% hydrogen peroxide. Took me a while to figure it out....but, I just add ~1/2 cup after each soak and stir. That gives me 5 months before the water/wood gets too slimy. We (family of 3) shower and thoroughly wash before each soak. When it comes time to clean the tub, I just drain the water on our landscaping. Plants thrive on it.
This tub has no jets, pumps, or filters. I'd really like to add a PV powered direct pump/filter system to remove the varying things that find their way in. I've just been using a head bug net. Not as slick as a solar filter would be but it works ok.
Re the feed and chimney pipe sizes: I've thought about this overnight and looked through Ianto's book again. I wonder if it could be analogous to putting a small tip on the end of a garden hose....creating high pressure....which, in the case of a smaller chimney, it might force the emissions out and through at a faster rate which pulls in air in at a faster rate Just thinking aloud here.........
Of course, I have no idea. Ianto seems pretty clear on the proportions though, and the chimney is smaller. Wish he would have explained his reasoning behind that.
Thanks. I just came in from looking at my pipe and it is thicker than my earlier guess. It's a whopping 5/16" thick!
Any thoughts on the size of the feed tube and chimney for my 14" pipe diameter? I see that Ianto recommends a 4" chimney for a smaller 5 gallon bucket. I reckon 6" would be roughly right for mine....but then would I need to have a bigger feed tube...like 8"?
I'm considering a pocket rocket for my 6' diameter sauna. I much prefer to use items I have on hand but will get different materials if what I have will not work well.
I have a 14" diameter x 24" long pipe. So, a couple inches bigger in diameter than a 5 gallon bucket. The steel on this pipe is thick - 1/8". I was thinking I could cut it to whatever length needed then weld on a bottom and top (holes for feed tube and chimney).
I also have a similarly heavy 6" steel pipe that could be used as the feed tube.
Lastly, I have lots of 6" stove pipe.
I have much experience with various wood stoves but only knowledge of rocket stoves. I assume a pocket rocket with a diameter of 14" will be plenty for the 6' diameter sauna, correct? (my idea was to surround the bottom half of the pocket rocket with rocks)
Will the 6" feed tube and 6" stove pipe work ok for my 14" pipe....or do the ratios need to be different?
I like to run my stove pipes vertically with no elbows. However, in the case of my sauna, it would be much easier for me if I were to run the stove pipe vertically about 3' then run it at a 90° through the wall then another 90° to get it vertical again. Will that work with a Pocket Rocket.....or is it critical I run the pipe vertical all the way? (if it matters, I'm concerned with smoke.... i.e., I'm hoping to have something that draws well so I won't have the smell of smoke (excessive) distracting from the experience)
Well, I have a full good winter on my system now. To cope with freezing issues, last fall I put a valve in so I could shut off the "first flush" during the winter and open in the spring. No issues at all. Went up to this locale this spring and found a tank full of water! So, I plumbed down to my yurt and now have running water. Super excited about that!
I'm contemplating one at a remote off-grid mountain location where it could go for weeks with no attention. I wouldn't think too much of it, however, rather than snow accumulating, with minimal (ie normal) freeze/thaw cycles, we've been encountering substantial melt during many mid-winter days and even rain. Yet, it's still freezing hard during most nights.
I can envision some problematic scenarios with a "first flush"...and have some ideas how to compensate. However, I would love to hear the experiences of others. Anyone?