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Rocket hot tub on skids for Wheaton Labs?

Erica Wisner

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posted 9 years ago

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I get that not everybody loves a hot tub, but I have a thought about how this could also function as a water reservoir.
We are in the middle of fire season in WA right now, and a stock tank full of water represents 1 easy refill for a small fire truck - a not unsubstantial asset. It would also represent the ability to stage water uphill of sensitive garden areas, or for washing-up, on the lab, even if it's not potable water.

I'm thinking about the skiddable structure having two shed roofs, one on each end, one for dry wood storage and one for a little changing room and the heater 'mechanical room'. Both shed roofs point inward, allowing them to help fill the tub when it rains. Still working on the lid design - either tule mats or a wooden cover, to allow water to drain inward but reduce evaporation and algae growth if it's stored over time.

The tub itself could be a round 'boughten' cedar tub, or a big stock tank, for now.

-Erica

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Eric Shortridge

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posted 9 years ago

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Hi, Eric from DirtRich Permaculture in Denver here. Very interested in helping to build a hot tub. Just need to get my logistics straight. What's needed from me etc. Let me know please. Thanks.

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Cassie Langstraat

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Eric Shortridge wrote:Hi, Eric from DirtRich Permaculture in Denver here. Very interested in helping to build a hot tub. Just need to get my logistics straight. What's needed from me etc. Let me know please. Thanks.

Eric,

Are you wanting to come out to wheaton labs before the event to help build one?

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Eric Shortridge

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Location: S. Denver Metro

posted 9 years ago

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Hi, Eric in Denver again. Thought of some more questions. Can I trade labor for attendance to the workshop? Can I bring and camp with my 11yo. daughter/lackey? Are you even interested in another crusty middle aged dude playing with fire and stuff up there? Added a link to my permacultureglobal.org profile.permacultureglobal.org Hope that's right. Has my bona fides. Thanks,e

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Peter van den Berg

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posted 9 years ago

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Maybe someone made this remark before so saying it again would be a bit silly.
But anyway: we all know a pocket rocket will get awfully hot, in the lower regions mostly. This rocket can't be immersed in water because the temperature of combustion would go down too much. And when this pocket rocket is placed inside another barrel which is immersed? just a thought.

regards, Peter

Eric Shortridge

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Location: S. Denver Metro

posted 9 years ago

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Yes Cassie, I would, I think it would be good knowledge and experience in general, and would expand my knowledge base to better service my clients.

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paul wheaton

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posted 9 years ago

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Eric Shortridge wrote:Hi, Eric in Denver again. Thought of some more questions. Can I trade labor for attendance to the workshop? Can I bring and camp with my 11yo. daughter/lackey? Are you even interested in another crusty middle aged dude playing with fire and stuff up there? Added a link to my permacultureglobal.org profile.permacultureglobal.org Hope that's right. Has my bona fides. Thanks,e

Yes. What you do is come before the event. We pay you for your labor, and then you use those funds to purchase a ticket.

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Eric Shortridge

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Location: S. Denver Metro

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"Yes. What you do is come before the event. We pay you for your labor, and then you use those funds to purchase a ticket." Paul.

That clears it up. Thanks.

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Eric Shortridge

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Location: S. Denver Metro

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Probably the wrong place for this question..could someone please point me in the right direction on the process of volunteering at the labs? Just showing up seems like folly and an opportunity for misunderstandings. Any assistance,anecdotal advice, or details of any kind would be greatly appreciated. Just trying to offer the help that was asked for. Thanks, hope to take part.

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Burra Maluca

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posted 9 years ago

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Try this thread - https://permies.com/t/46350/labs/gapper-program

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Eric Shortridge

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Location: S. Denver Metro

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Thank you kindly.

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Jesse Grimes

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posted 9 years ago

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It's not exactly going to be a skidable hot tub, but I just picked up this free cast iron tub and I am hoping to make a rocket mass water heater for it. Perhaps you wold like to help me tinker with it. My current plan is to wrap the exhaust tubes around and close to the tub, and surround the whole thing in a thick cob mass. I will also run a soft copper pipe from the bottom of the tub, coiled upwards around the barrel and then back into the top of the tub. Hopefully this will create a thermosiphon to circulate the water enough to heat it relatively quickly, and the heated mass around the tub should help to keep the water hot for a nice long soak. The bath tub itself will act as an open to atmosphere water resevoir, so there shouldn't be any risk of boom squish, I think. Am I on the wrong track with any of this? I could use help with some sort of safety device to ensure that the water coming off of the barrel isn't scalding hot when it enters the tub. Any ideas?

Cast-iron-tub.jpg

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Dave Dahlsrud

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posted 9 years ago

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Jesse
What about discharging the hot water into another tub or bucket (or whatever), and then having that spill over into the main soaking tub. You might have to experiment with the size, etc to get the right temperature of water coming out of the tempering tub, but I think exposure to the atmosphere and having an insulated primary discharge might just be enough to keep the thing from scalding you. I hope that makes sense. A nice pleasant waterfall effect could be pretty relaxing while you're enjoying that long hot soak!

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Jesse Grimes

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Thank you Dave. That makes a lot of sense. After reading your post I was imagining that I might even be able to regulate the temperature by chaging the "shape" of the waterfall. If it were a wide thin layer of water, i.e. lots of surface area, it would cool down more quickly as it fell. If it were a thicker stream it would retain more heat as it traveled into the tub.

Jocelyn Campbell

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Frank Lee wrote:When I click on your email link I am taken to the last post in the topic and need to scroll to the top to sign in. Then I'm taken to the list of topics so need to go back to email and click the link again. Irritating.

Even though this is a bit off topic, it might help others to know that there is a wee little box you can check when you log in that will keep you logged in. Meaning, the next time you follow a daily-ish e-mail link you won't have to log in again to reply!

Back on topic, there is still room in the innovators events starting next week (Oct. 7, 2015) here in Montana! See http://richsoil.com/rmh-innovators.jsp for details or to sign up.

Erica's idea for a RMH hot tub is superb and she really wants more on topic conversation before next week. Paul wants the hot tub skiddable and with the least toxic materials and all that.

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Erica Wisner

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Peter van den Berg wrote:Maybe someone made this remark before so saying it again would be a bit silly.
But anyway: we all know a pocket rocket will get awfully hot, in the lower regions mostly. This rocket can't be immersed in water because the temperature of combustion would go down too much. And when this pocket rocket is placed inside another barrel which is immersed? just a thought.

That's very much along the lines I'm thinking for a super-simple version. Second barrel, probably lined with mud/brick and we play with the thickness and materials between the two barrels to transfer heat not too fast from the fire, not too slow for efficiency.

I'd also like to build a feed tube that lasts longer than the stovepipe often used in pocket rockets, maybe by casting a refractory firebox inside a barrel.

Those are two simple versions we can make in a day or two, if there's a big tub of water to stick them in and see if they work. Maybe Jesse'd be willing to drag that tub down for us to play with.

Eric - Much appreciate the offer of help!
Have you worked anything out with Paul about coming in ahead of the event to work on this? We will be arriving on site the 5th or so, with a few days to tinker even before the tinkerer's event.

- Erica

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paul wheaton

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I've banned the use of pocket rockets here because the feed tubes burn out so fast. If you can solve that problem, then I would be glad to modify the ban.

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Weston Ginther

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Location: NW South Dakota - Zone 4b

posted 9 years ago

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The rocket hot tub is starting to see some initial progress.

I was able to find a used redwood hot tub on Craigslist over in Spokane. So after a little bit of a road trip I arrived back at Base camp with a hot tub that fits Paul's standards of aesthetics and natural materials.

Unfortunately the guy had started taking it apart just a few hours before I called so it is currently disassembled. Also, the hot tub sat empty for a couple years and is experiencing some deterioration. However, because of those two factors we were able to buy it for super cheap. Since Ernie has experience with building and maintaining boats, we are pretty certain we can get the hot tub to hold water. I believe the current plan is to use a mixture of raw linseed oil and lime to make a water sealant putty for the areas between the boards that are starting to rot.

Like with most structures here at Wheaton Labs, the hot tub is being placed on a skiddable platform. I dragged the logs for the skids down to the shop today and will start assembling the skiddable platform tomorrow. While I work on the platform, Erica will be developing a game plan to put the humpty-dumpty hot tub back together again.

As of a couple days ago, the exact heating system design hadn't been finalized so either Erica or I will be posting further updates in the coming days (along with more pictures

)

Hot-tub-parts-(the-pieces-on-the-tarp).jpg

3-logs-for-the-skids-(may-only-use-2-for-skids).jpg

Julia Winter

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So exciting!

Thanks so much for the update. What you have there is exactly what we are dreaming about, over here in Portland. Can't wait to see what you come up with!

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diana todd

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posted 9 years ago

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My husband built us a hot tub. We used a galvanized livestock tank, an old dysfunctional hot water heater. He pulled the sheath and insulation off of the water heater, dug a big fire pit hole to place the water heater in the hole then covered the hole with 25' steel plates, ran a water lines out of water heater at the top and a water line from the bottom of the horse tank to the water heater. Hot rises and cold sinks so it self circulates.

We have used it three years now and just love it.

It takes a few hours for the tank to heat up after starting the fire. Not as efficient as your rocket heat will be but we just LOVE it.

We set the tank on two old concrete slas that we moved with the tractor

Visitors enjoy it also.

Rusty Bowman

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Location: Idaho

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posted 8 years ago

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Hi,

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.

Cheers to Hot Water!!

Best with the project.

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Alex Colchester

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posted 7 years ago

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Hi

We have solved using a rocket stove to heat a hot tub and our system is tested over a year with zero issues. Check out my threads.

There is a lot of misinformation out there, with people very sure that it is very dangerous to heat water with a rocket stove. The whole flash to steam/ 'boom squish' thing is way overstated. We put water in the direct flame path of the rocket at 1100F and see absolutely no problems. We have a safety valve fitted just in case, but it has never triggered in 1 year of using the heater at full rocket burn temperature. Also, the idea that the rocket becomes smoky due to the cold water is also untrue. We maintain almost nil smoke emission even after starting the burn and heating water that is very cold.

Of course, if you fill a container with water and seal it and put it on a heat source you will make a bomb and possibly cause serious injury. But that will be true whatever your heat source (rocket or otherwise) and is not a specific concern of rocket stoves.

We engineer our water heating tank to be extremely safe with the use of very large bore pipes (almost impossible to block unwittingly) and the use of a pressure safety valve (probably overkill, but best to be safe).

It would be great to have feedback from the permies community, but it seems that for some reason people aren't interested in my developments, perhaps because I am an outsider to the 'permies scene'.

Thanks for all feedback in advance

Alex

Pellet-stove-hot-tub.jpg

Alex Colchester

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posted 7 years ago

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... And it is worth noting that our system heats 1000 litres of water from well cold to 39celsius in 3 hrs using 20lbs of wood pellets. Far less fuel than many of the previous posts are suggesting is required. I note someone saying thay needed 500lbs of wood!

Julia Winter

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Alex Colchester wrote:
We have solved using a rocket stove to heat a hot tub and our system is tested over a year with zero issues. Check out my threads.
[snip]
It would be great to have feedback from the permies community, but it seems that for some reason people aren't interested in my developments, perhaps because I am an outsider to the 'permies scene'.

You can find Alex's original thread describing his rocket heated hot tub here: https://permies.com/t/69707/Engineered-Modular-Rocket-Stove-Hot

Alex, I doubt the lack of response has much to do with your insider or outsider status. This is a huge site, and sometimes cool things get lost in the river of new posts. Putting a link in a related thread is a good strategy for generating feedback. I'm not going to comment on your design because I know very little about designing rocket stoves, but I'm always interested in an eco-friendly hot tub!!

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Russell Dinning

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Doing some mods to my 4 inch batch out door bath ill add some pictures as i go may help some more inspiration come out

Julia Winter

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Excellent - love to hear all ideas and particularly successes with wood heated hot tubs. I am still hoping to get one!

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Russell Dinning

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Here's a few pictures of my batch bath not exactly portable.
It will heat 2/3 of that cast iron bath to almost too hot to get in temperature ( and i looove a hot bath) in 1.5 to 2 hrs from about 8 degrees c.
At a guess its bout 200litres maybe more.
Using approximately half a wheelbarrow of not completely seasoned macarocarpa.
Modifications i have done to last build is
Broken a section of riser out of about 200mm to allow the flames to exit lower and be directed more towards the bath.
Added fully insulated box around the riser right down to the top of the firebox.
And lowered the bell above the riser to same height as the bath.
Heats up 3 x as fast now.
Specs
4 inch peterberg batch made to precise dimensions.
Secondary air supplied through stainless steel angle iron replacing the masonry angle sections in the bottom of the fire box.
About 15% more internal surface area inside bath bell than recommended for a 4 inch.
4 m 1/2 inch tubing from the bottom of bath through the bell forming a coil insidethe bell and entering the bath about half way up the side.

20171108_181610.jpg

View-inside-insulated-box-with-thermosyphon.jpg

Still-no-bricks.jpg

Bricks-complete-with-flue-preheating-simple-rocket-dry-stacked-bricks.jpg

Joachim Brunson

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posted 5 years ago

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Hello,

I’ve been working on this design for a rocket mass heater hot tub. This design is also boiler. Attached are basic diagrams to show the concept not the actual build. It seems to me that most of the designs i see are inefficient and sluff off too much heat and would require hours to heat up.
However I would like some feedback on any pros or cons to this concept.

We ran some numbers and suspect it would take about 45 min to heat 140 gal with this design.

One con being that it could get too hot.

Aslo im not sure if the coil above the fire would cause problems for the function of the mass heater.

Please let me know what you think.
Thanks!

Rocket-heated-hot-tub-design-1.jpeg

Rocket-heated-hot-tub-design-2.jpeg

Steve Boyd

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Location: Tasman, New Zealand

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Unless you plan to force the water to circulate you may have a bomb on your hands!!
Cold inlet to coil need to be from the bottom of tub to bottom of coil, hot outlet at top of coil. to top of tub.
Tub needs to be higher.
Horizontal coil might work if circulation pump used - a pump failure could be catastrophic though
Steve

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Joachim Brunson

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Thanks Steve!

This is true!
My intention was to use one-way-valves on the inlet and outlet. (The diagram was not intended to show pluming details) And to also include a drain at the lowest point and pressure valve at the highest point. My question about your recommendation is: wouldn’t it be difficult to heat the tub to it’s depth if the hot is mostly at the top of the pool, being that heat rises?

Steve Boyd

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i doubt one way valves would save you from an explosion.
There would be some stratification of the water in the tub but a quick stir, people in the tub, would solve that

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Julia Winter

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I think the first design will heat better. Getting a tub coiled like that is super tricky, and where my plans all broke down when I looked into this a couple of years ago.

I don't see water under pressure here (the surface of the tub is open) so I'm not seeing the boom-squish risk. Can someone point that out?

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Steve Boyd

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Hot water rises, cold water goes to the bottom. Inlet and outlets in these designs are both in wrong place. Tub should be higher than coil etc etc. Huge potential for explosions here - with both designs.

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Joachim Brunson

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Thanks Juila,

I think so too.
One way to make a good coil is to fill the the pipe with sand. That prevents buckling and flattening.

Also as far a Steve’s comments I still don’t see it... the rmh and water lines are open ended, there is no place for pressure to build. Heat will circulate the water through the boiler. With the lines switched the bottom of the tub will remain cold.

shiwen he

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Location: USA

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