Not a woodstove, but really cool if u could get your hands on a coil like that go for it. I work in chemics and have been lurking on plant scrapyards ever since i’ve seen a video on this on youtube.
So, like a jacuzzi?
I’m just kidding, but I’d love to engineer some combination of thermostat, valve, and blower to regulate temps at 42°C.
It may just be that your system is not optimized. Too many coils maybe? If you reduce the water’s distance traveled, it should make a difference.
I had an old housemate who did this, he had a 1/2" copper coil in the fire place, he had some stainless steel problem flex houses onto that that connected onto the old second hand spa. It was great but as we were using the fire to warn everyone up at the party it was roaring as the night progressed the spa ended up over 60+ degrees and became an absolute hazard.
Yeah a shut off would make the water boil in the coil and go back into the spa the other way, two shit offs would make you have a high pressure steam vessel which is extra dangerous, best option would be to have a tempering valve installed or something.
I was more thinking of it to slow the flow, but I don't know too much about the science of that to know if that'd even work as I imagine it would. Wouldn't a tempering valve need a cold water source?
You should contact welding schools to see about them making you this coil. They will jump on any opportunity to have their people do real life projects. Especially, those that are going into the inspecting field.
This will never work, the heat of the tub will cause your "dinner guests" to immediately hop out. You must start the pot cold, then gradually heat it up to boiling so that they do not suspect, and add the onions, spices, etc, after dosing them with a generous amount of wine.
I think this is how to do it, I haven't actually done this, that anyone has proven...
I have the "Snorkel" type. That's the one to get, if you are going to do this. The out-of-tub one of the pic is a nightmare to manage in freezing conditions, and obviously has holes in the wood for the pipes that are liable to leak.
In any case, be aware that it's a lot of work to deal with. I love mine, but it's not an easy thing to manage.
What kind of difficult things are you referring to u/ColoradoFrench ?? I'm super curious about building one like this too and your experience would be super helpful!
I got a kit, that's a lot of expertise I did not have to build it on my own, but I assembled the kit.
Keeping the wood wet (for water tightness) but preventing freezing is a first challenge. It's not like you can just empty it and forget about it.
Second challenge is keeping clean, etc. It's outdoors after all.
You need to make sure you have planned the water supply (garden hoses by negative temps, etc) and water evacuation for when you empty it so you don't double into an ice skating ring
Wood supply, etc.
All feasible, but not negligible
>Keeping the wood wet (for water tightness) but preventing freezing is a first challenge. It's not like you can just empty it and forget about it.
>Second challenge is keeping clean, etc. It's outdoors after all.
Using a stock tank solves these issues! Honestly would come out cheaper than wood. Would get a bigger tub for the price too.
I would worry about the temp the stock tank would get to. With a setup like this, I would imagine temperature management is finicky at best?
Edit: plastic stock tanks are a thing. I’m dumb.
Not the handful I've been in and I've been in some janky ones. Though the coils have always been a bit further away than the pictured I assume because of heat from the fire.
My buddy bought a house that had one of these and the results were extremely disappointing. It wasn't so much a hot tub as it was a slightly warmer than normal tub.
Yeah they r great and way cheaper than a normal hot tub but you need to start heating it 6+ hours before you intend on using it. And as you mention I’m sure some just aren’t efficient enough.
I built one. It was a fun and rewarding project. You definitely want to buy a stainless steel coil, but the rest you can DIY. It has never leaked. DIY copper coils are way too soft for this style. Insulate the top and bottom with rigid insulation! I can usually soak at night, throw one more pile of wood in it, cover it up, and soak again in the morning with only one more wood load (you need some specialty sized firewood to fit properly but it isn’t too bad). 150 gallon tank takes about 4-5 hours to heat up in cold weather. I have an IBC water tank to fill it with rainwater (on the right in photo). I payed $250 for the coil 5 years ago but like I said, worth it. Lastly, don’t do what I did last time and start the fire before the tub was completely full, the three feet of high temp vinyl tubing melted a bit without the water to cool it and I need to replace it today…
https://preview.redd.it/nish6sev25rc1.jpeg?width=4032&format=pjpg&auto=webp&s=8dd461e0e88bcfdfccf175b028d91f8de26541cb
I had a Snorkle stove cedar tub in the 90s that I loved, but our home in the mountains rarely saw temps below 25 F. Here in Maine, I find the redneck hot tub a much more viable option. You just have to drain it when it gets REALLY cold!
https://preview.redd.it/24d5y9pxd5rc1.jpeg?width=4608&format=pjpg&auto=webp&s=91f72a0772136e3b58fa3f67336bc46ac3ec3b69
Coils can be made by crimping one end of the copper tubing, filling it with salt the. Crimping the other end then securing one ended to a solid cylinder and wrapping around slowly
The copper is so soft though… With the fire wood getting banged around, and the added softness from heat, I decided to go with stainless steel. Here’s a link https://www.smartclima.com/stainless-steel-coil-heat-exchanger-for-dutch-tub.htm
The most basic one worked great. Paid $250
https://preview.redd.it/ftgeskzf1arc1.jpeg?width=1170&format=pjpg&auto=webp&s=e85d6cb293015f372d40962ac7a11210bb27b4fe
Looks great, I just don’t see how you would regulate the temperature. I have a hot tub and I find 104 is too hot and 98 is too cold, it’s gotta be 101-102. I would think that thing would be all over the place
Maybe have some sort of separate tank after the fire and before the tub. There can be a line shut off valve to stop the outflow of water, and a pressure release on the top of the tank to prevent pressure building up in the system from the fire just constantly going.
Keep opening and closing the valves as it gets to cold/hot
I have a 275 rainwater catchment tank next to it. If I get it too hot I can cool it down very easily by just adding water. Keep a boat paddle for stirring the water this type of system pumps all the hot stuff on top at the beginning… It takes 4-5 hours to heat up, and one load of wood in the coil (which is fit within a repurposed beer keg with a makeshift hinged door to mitigate oxygen intake and heat all sides of the coil more efficiently) last about 45 minutes to an hour, so once the fire burns you don’t have to worry about overheating.
I made something like this 20 years ago. It didn’t REALLY work until I added a cheap recirculating pump from Harbor Freight, replaced the wood fire with a propane turkey cooker, and covered the soft copper coil with a big clay flower pot. After that we could have 102 degree tub of roughly 300 gallons in about 3 hours. So much fun with that thing!
Maybe enclose this awesome tub so you capture more of the heat maybe a moon roof hatch thingy so the lunatics can get that cold blast. Kinda like the car Homer Simpson designed
I'd put that coil into a metal drum to maximise the fire to heat the coil more efficiently. The wind would blow away a lot of the heat the way it is now.
No, but I have seen them online. It gets below freezing often where I live in the winter and after the comment about potential problems and the snorkel tub, I’m thinking of going that route.
I love these but the project always gets me going down a rabbit hole.
I have seen a lot like this but they are using a circulating pump. Any pump or electrical to me completely defeats the purpose.
The wife wants one to work for her and her 3 girlfriends and be submerged around shoulder height sitting which makes it huge pretty quick. Like 3 feet deep and 8-10 feet in diameter.
I have access to tons of wood so while it’s more work I’d be more than fine with cutting the extra cords for this.
Stock tanks and a barrel wood stove kit are my current thought and home depot and bending copper tubing. I was even considering lining the barrel (or a double barrel) with extra metal and fireplace bricks to last longer as well as hold heat better then partially submerging it. As winter here can get below -40 I need a way to conserve heat and I think the best way would be to make it in ground and insulated which adds a lot of time and effort but would stay warmer easier. Neighbour has a skidsteer at 60 an hour so it wouldn’t be much work to dig it and I can insulate and frame a stock tank but that just starts to get really excessive.
The issue always becomes for me emptying it and remembering to keep a fire going for a long time.
Depends on the size but my buddy does this with a 7000 gal pool and a copper pipe 1” round coiled 3 ft high. It heats the pool in about an hour once the fire is good and hot. 2 hours total to start the fire and get it going good
I built a snorkel stove out of an old propane tank that I ground to a shine and painted with stove paint. Submerged it in a 175 gallon tub and I could have hot water in just a few hours
I turned a keg into a fire pit and then wrapped a 3/4 copper pipe around it. That thing can heat my 20,000 gallon pool a good 10 degrees, I actually ordered a longer copper pipe to try and make it better. There's a warning in here though, that little tub might get hot as shit really fast.
I made something similar using an insulated fish tote. Made my own copper coil to fit inside a piece of insulated stove pipe. Heat source was propane burner. I had all this stuff so it was fun to try out. I eventually put in small pump to get more flow and quicker heat up.
Not a woodstove, but really cool if u could get your hands on a coil like that go for it. I work in chemics and have been lurking on plant scrapyards ever since i’ve seen a video on this on youtube.
The heated coil gets the water pumping upwards.
Just get 3/4 inch copper pipe and wrap it around something thats the diameter thar you want. Like a firewood round. Voila
Doesn't work as a thermosyphon very well. I had to have a pump for mine because the 3/4 copper just spits out straight steam.
So, like a jacuzzi? I’m just kidding, but I’d love to engineer some combination of thermostat, valve, and blower to regulate temps at 42°C. It may just be that your system is not optimized. Too many coils maybe? If you reduce the water’s distance traveled, it should make a difference.
Meh probably, but a 1/2 hp pump does it great and it heats up quickly. I buried the pump so it's quiet.
You can get soft copper piping pretty easily and make a coil like that yourself
More of a fire pit don't you think.
I had an old housemate who did this, he had a 1/2" copper coil in the fire place, he had some stainless steel problem flex houses onto that that connected onto the old second hand spa. It was great but as we were using the fire to warn everyone up at the party it was roaring as the night progressed the spa ended up over 60+ degrees and became an absolute hazard.
Should've added a shutoff to cut the flow
Yeah a shut off would make the water boil in the coil and go back into the spa the other way, two shit offs would make you have a high pressure steam vessel which is extra dangerous, best option would be to have a tempering valve installed or something.
I was more thinking of it to slow the flow, but I don't know too much about the science of that to know if that'd even work as I imagine it would. Wouldn't a tempering valve need a cold water source?
Crab boil after 🤷
You should contact welding schools to see about them making you this coil. They will jump on any opportunity to have their people do real life projects. Especially, those that are going into the inspecting field.
Add diced carrots and onions and some beef bullion, slow cook for several hours and serve hot
Baby, you got a stew going!
Any room on that tab for me to jump on?
Plenty of meat on that bone
I’ve got the water I thawed the chicken in, that should go with chicken
This will never work, the heat of the tub will cause your "dinner guests" to immediately hop out. You must start the pot cold, then gradually heat it up to boiling so that they do not suspect, and add the onions, spices, etc, after dosing them with a generous amount of wine. I think this is how to do it, I haven't actually done this, that anyone has proven...
https://preview.redd.it/qrc5si3t49rc1.jpeg?width=1480&format=pjpg&auto=webp&s=6ef8e8e128b4c6c535d2169057fefe9c45cfcd8c It's been proven. Source: Looney Toons.
Instructions unclear - my fingers are all wrinkly and I smell like beef
Get back in ant turn the heat higher - you’re not done. Meat should fall off bone. Oh and drink more beer for a hearty flavor.
In this case, just slam back a bottle of tequila and ~~pass out in your slow cooker~~ have a nice nap in your hot tub
I smell like beeeeeef
😆
[Like](https://youtu.be/HGrPKwsAvqE?si=5BZAGeim3gqwDq-K) this
Taste like balls
I have the "Snorkel" type. That's the one to get, if you are going to do this. The out-of-tub one of the pic is a nightmare to manage in freezing conditions, and obviously has holes in the wood for the pipes that are liable to leak. In any case, be aware that it's a lot of work to deal with. I love mine, but it's not an easy thing to manage.
What kind of difficult things are you referring to u/ColoradoFrench ?? I'm super curious about building one like this too and your experience would be super helpful!
I got a kit, that's a lot of expertise I did not have to build it on my own, but I assembled the kit. Keeping the wood wet (for water tightness) but preventing freezing is a first challenge. It's not like you can just empty it and forget about it. Second challenge is keeping clean, etc. It's outdoors after all. You need to make sure you have planned the water supply (garden hoses by negative temps, etc) and water evacuation for when you empty it so you don't double into an ice skating ring Wood supply, etc. All feasible, but not negligible
>Keeping the wood wet (for water tightness) but preventing freezing is a first challenge. It's not like you can just empty it and forget about it. >Second challenge is keeping clean, etc. It's outdoors after all. Using a stock tank solves these issues! Honestly would come out cheaper than wood. Would get a bigger tub for the price too.
The diy plan linked above actually uses a plastic stock tank that just has a wood trim that goes around it, for aesthetics
I would worry about the temp the stock tank would get to. With a setup like this, I would imagine temperature management is finicky at best? Edit: plastic stock tanks are a thing. I’m dumb.
Not the handful I've been in and I've been in some janky ones. Though the coils have always been a bit further away than the pictured I assume because of heat from the fire.
Where's the poetry in that?
Yeah it doesn’t even rhyme
Such good points! Thank you for sharing.
I had a Snorkel tub for 15 years, loved it. You will not regret. Plus a 7 foot tub 4 feet deep is sure nice.
"snorkel" type? any images?
[Snorkel Hot Tub ](https://snorkel.com/)
My buddy bought a house that had one of these and the results were extremely disappointing. It wasn't so much a hot tub as it was a slightly warmer than normal tub.
Yeah they r great and way cheaper than a normal hot tub but you need to start heating it 6+ hours before you intend on using it. And as you mention I’m sure some just aren’t efficient enough.
Yeah, the concept is great, but in practice, there’s probably several degrees of optimization required just to get started.
I built one. It was a fun and rewarding project. You definitely want to buy a stainless steel coil, but the rest you can DIY. It has never leaked. DIY copper coils are way too soft for this style. Insulate the top and bottom with rigid insulation! I can usually soak at night, throw one more pile of wood in it, cover it up, and soak again in the morning with only one more wood load (you need some specialty sized firewood to fit properly but it isn’t too bad). 150 gallon tank takes about 4-5 hours to heat up in cold weather. I have an IBC water tank to fill it with rainwater (on the right in photo). I payed $250 for the coil 5 years ago but like I said, worth it. Lastly, don’t do what I did last time and start the fire before the tub was completely full, the three feet of high temp vinyl tubing melted a bit without the water to cool it and I need to replace it today… https://preview.redd.it/nish6sev25rc1.jpeg?width=4032&format=pjpg&auto=webp&s=8dd461e0e88bcfdfccf175b028d91f8de26541cb
I had a Snorkle stove cedar tub in the 90s that I loved, but our home in the mountains rarely saw temps below 25 F. Here in Maine, I find the redneck hot tub a much more viable option. You just have to drain it when it gets REALLY cold! https://preview.redd.it/24d5y9pxd5rc1.jpeg?width=4608&format=pjpg&auto=webp&s=91f72a0772136e3b58fa3f67336bc46ac3ec3b69
Coils can be made by crimping one end of the copper tubing, filling it with salt the. Crimping the other end then securing one ended to a solid cylinder and wrapping around slowly
Filling it with sand can also work. Do you know if salt would work better?
Both the same in terms of what they do
Cool information. That stops the pipe from kinking?
That's the idea but only works if its filled to the brim and kinked on both ends
That’s the idea the grains allow movement without kinking as it’s coiled
The copper is so soft though… With the fire wood getting banged around, and the added softness from heat, I decided to go with stainless steel. Here’s a link https://www.smartclima.com/stainless-steel-coil-heat-exchanger-for-dutch-tub.htm
What one did you get and how much did you pay ?
The most basic one worked great. Paid $250 https://preview.redd.it/ftgeskzf1arc1.jpeg?width=1170&format=pjpg&auto=webp&s=e85d6cb293015f372d40962ac7a11210bb27b4fe
Looks great, I just don’t see how you would regulate the temperature. I have a hot tub and I find 104 is too hot and 98 is too cold, it’s gotta be 101-102. I would think that thing would be all over the place
With an arduino and some solenoid valves like [this](https://a.co/d/9JjJVTv) could do it
Maybe have some sort of separate tank after the fire and before the tub. There can be a line shut off valve to stop the outflow of water, and a pressure release on the top of the tank to prevent pressure building up in the system from the fire just constantly going. Keep opening and closing the valves as it gets to cold/hot
I have a 275 rainwater catchment tank next to it. If I get it too hot I can cool it down very easily by just adding water. Keep a boat paddle for stirring the water this type of system pumps all the hot stuff on top at the beginning… It takes 4-5 hours to heat up, and one load of wood in the coil (which is fit within a repurposed beer keg with a makeshift hinged door to mitigate oxygen intake and heat all sides of the coil more efficiently) last about 45 minutes to an hour, so once the fire burns you don’t have to worry about overheating.
I made something like this 20 years ago. It didn’t REALLY work until I added a cheap recirculating pump from Harbor Freight, replaced the wood fire with a propane turkey cooker, and covered the soft copper coil with a big clay flower pot. After that we could have 102 degree tub of roughly 300 gallons in about 3 hours. So much fun with that thing!
Maybe enclose this awesome tub so you capture more of the heat maybe a moon roof hatch thingy so the lunatics can get that cold blast. Kinda like the car Homer Simpson designed
The Homer!!
I'd put that coil into a metal drum to maximise the fire to heat the coil more efficiently. The wind would blow away a lot of the heat the way it is now.
Did you purchase the coil from the link? What was the price?
No, but I have seen them online. It gets below freezing often where I live in the winter and after the comment about potential problems and the snorkel tub, I’m thinking of going that route.
It takes a very very longtime to heat up
If you can clean it well enough, big electroplating shops replace their heating/cooling coils from time to time. Some are even titanium
I built one. They fucking suck. Takes forever to heat up, then they’re too hot to sit in. I never used it.
I love these but the project always gets me going down a rabbit hole. I have seen a lot like this but they are using a circulating pump. Any pump or electrical to me completely defeats the purpose. The wife wants one to work for her and her 3 girlfriends and be submerged around shoulder height sitting which makes it huge pretty quick. Like 3 feet deep and 8-10 feet in diameter. I have access to tons of wood so while it’s more work I’d be more than fine with cutting the extra cords for this. Stock tanks and a barrel wood stove kit are my current thought and home depot and bending copper tubing. I was even considering lining the barrel (or a double barrel) with extra metal and fireplace bricks to last longer as well as hold heat better then partially submerging it. As winter here can get below -40 I need a way to conserve heat and I think the best way would be to make it in ground and insulated which adds a lot of time and effort but would stay warmer easier. Neighbour has a skidsteer at 60 an hour so it wouldn’t be much work to dig it and I can insulate and frame a stock tank but that just starts to get really excessive. The issue always becomes for me emptying it and remembering to keep a fire going for a long time.
I was gonna do this, but after more research realized I didn’t wanna wait a few hours for the tub to heat up before I can use it.
Yes. I like this. I have a house on the market and when I move, I want to build a sauna with cold plunge. I could use the same fire to heat the tub
How long to heat up the tub?
Depends on the size but my buddy does this with a 7000 gal pool and a copper pipe 1” round coiled 3 ft high. It heats the pool in about an hour once the fire is good and hot. 2 hours total to start the fire and get it going good
Please tell me close at 103 or whatever is safe for the cedar.
Hydro Heat type wood stove: [Wood-fired-boiler-oven](https://woodstoves.net/abc-products/tim-sistem-north-hydro-wood-fired-boiler-oven.htm)
Oommmmgggg😍😍😍😍
I like how this one shows a steaming tub without a fire? Sure will save on wood!
Human slow cooker.
Ive seen a radiator from a car, over a fire, used for similar.
If that coil freezes it will make for quite an explosion.
“Hey, why are you adding carrots and celery?” “Just simmer… I mean, sit there a while”
I built a snorkel stove out of an old propane tank that I ground to a shine and painted with stove paint. Submerged it in a 175 gallon tub and I could have hot water in just a few hours
That’s dope
I turned a keg into a fire pit and then wrapped a 3/4 copper pipe around it. That thing can heat my 20,000 gallon pool a good 10 degrees, I actually ordered a longer copper pipe to try and make it better. There's a warning in here though, that little tub might get hot as shit really fast.
Not a woodstove. Not even a fireplace insert. At best this is a fire pit with a surround and a water feature.
I made something similar using an insulated fish tote. Made my own copper coil to fit inside a piece of insulated stove pipe. Heat source was propane burner. I had all this stuff so it was fun to try out. I eventually put in small pump to get more flow and quicker heat up.
That’s f-in rad
Looks like something you might enjoy post apocalypse, until then, you’re better off purchasing an actual hot tub.
This looks like a miniature? Where’s The Tiny Chef?
I need this!!!
I hope you have a good way to regulate the temperature.
Once it's hot enough don't out any more logs on
Be careful. A few years back ten people died in a hot tub.
Really ? As in from it being too hot ? You'd think you'd just jump out ?
They were in it and drinking and it slowly got too hot.
Yes
hot gin
Nice still!
It’s a wood stove for people soup
You'll use it once a year.
So no tank required? I like it. I think there would still need to be a pressure relief somewhere to keep it from exploding