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Small Cabin Forum / Off-Grid Living / Building a hot tub
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Chinook92
Member
# Posted: 8 Sep 2021 04:20
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I want to build a wood fired hot tub

I have the heater concept down pretty well, a dozen or so loops of copper tube in a barrel stove should be fine, and obviously the inlet on the bottom with a drain to keep things from freezing when not in use and the outlet on top

The tub is the issue I am having

I was recently at the hot springs up here in Sitka Alaska and they were hands down the most amazing thing I have felt in years so having a hot tub is mandatory for my property now

The tub is the issue

Could do a stock tank, but I hear the galvanized tanks leach zinc. Plastic is questionable, don’t want a standard bath tub unless it’s a cast iron and enamel, fiberglass tubs are a no go. Same with epoxy coated plywood tubs….. I’ve been in the boat building/repair industry for too long and I want a certain level of purity to my hot tub

Wood is my next option but just not sure how
To go about it

For size a 5x8 is more than enough but just not sure how to make one….

Brettny
Member
# Posted: 8 Sep 2021 15:17
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They make them out of cedar. There prety pricy though.

gcrank1
Member
# Posted: 8 Sep 2021 15:29
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Barrel making is waayyy beyond my pay grade for rough carpentry.

fiftyfifty
Member
# Posted: 8 Sep 2021 17:54 - Edited by: fiftyfifty
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Here is something really DIY, but maybe too lowbrow, and it does have a plastic liner? http://thehomesteadingboards.com/diy-pallet-hot-tub/

ICC
Member
# Posted: 8 Sep 2021 17:59
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Quoting: fiftyfifty
and it does have a plastic liner?

...maybe use food grade?

Chinook92
Member
# Posted: 8 Sep 2021 19:41
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Very very very hesitant to use plastic but found HDPE open top tubs made in Idaho between 5-800 something bucks that’s potable water grade that I might just get and put in a cedar liner at my leisure with benches and stuff and use a 55gal barrel stove with copper coils inside and a circulation pump

https://www.tankandbarrel.com/open-top-water-tanks-crmi-700ott-custom-roto-molding-70 0-gallon-open-top-tank-p-1929.html

jhp
Member
# Posted: 9 Sep 2021 08:21
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I see hot tubs all the time on craigslist for free if you'll get rid of them. Most of them the tubs are good and the pump or other mechanicals are bad.

I'd probably go that route, save the cash for building a nice deck around it to hide the ugly parts.

Maybe contact a local spa and hot tub place and tell them what you're looking for and get a demo'd tub delivered for cheap?

FishHog
Member
# Posted: 9 Sep 2021 09:27
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Is a bit of zinc exposure a problem? I know many people ingest it as a suppliment

KelVarnsen
Member
# Posted: 9 Sep 2021 11:41 - Edited by: KelVarnsen
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I saved these pics from a Kijiji ad a couple of years ago. There is a welder in the town next to my cabin that was making (EDIT) aluminum hot tubs. He was asking $3000 Canadian. I really wanted one but it wasn't on the priority list.
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littlesalmon4
Member
# Posted: 9 Sep 2021 11:53
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This is what we have. It is marine grade aluminum wrapped with cedar. It also has cedar benches installed inside. We have had it since 2007 with no complaints

https://alumitubs.com/

I can post some pictures if you are interested.

FishHog
Member
# Posted: 9 Sep 2021 13:09
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Quoting: KelVarnsen
I saved these pics from a Kijiji ad a couple of years ago. There is a welder in the town next to my cabin that was making stainless steel hot tubs. He was asking $3000 Canadian. I really wanted one but it wasn't on the priority list.


That's pretty cool. I think you should move it up on your priority list.

NorthRick
Member
# Posted: 9 Sep 2021 13:11
Reply 


Look at snorkel tubs for ideas https://snorkel.com/.

Cedar tubs with a submerged wood stove for heat. Been thinking about something similar myself but haven't found the time.

Al Burton
Member
# Posted: 9 Sep 2021 13:32
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I have built 4 of them now. Pretty easy really. They were all made out of spf 2x6 cut into staves. Floor was either doweled or t&g. All had liners.
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gcrank1
Member
# Posted: 9 Sep 2021 14:24
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you might be able to acquire a stainless steel dairy tank used.

Rickkrus
Member
# Posted: 9 Sep 2021 14:49
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I have used a galvanized stock tank for years. It’s up on cement blocks and I build a fire under it. Zinc melts/burns so build several huge fires under it prior to using it and you will be fine. Cheap way to go it’s wonderful on starry winter nights.

BenJack9903
Member
# Posted: 21 Aug 2023 08:56
Reply 


I BUILT ONE!!! It's an 8'x8', cinder block, concrete floor, painted with pool epoxy paint, complete with skimmer, pump and sand filter. My cousin welded me a homemade version of a snorkel stove (aluminum) and it worked... "great". I say "great" and not GREAT! because there are some issues:
1. I didn't account for the stove floating and I have no way to attach it to the tub. I ended up constructing a table with 20 gallons of concrete in the base to tie the stove down to. Worked fine but all the "fixtures" to attach the stove to the table are not aluminum. These points created rust and rust is hard to deal with in a hot tub.
2. Takes a while to heat up. 880 gallons of water with the snorkel stove AND a "bubble thermal cover" takes about 8 hours to go from 45 degree water to 100 degree water. This pretty much means it's a Saturday only heater. I work in my shop on Saturdays so when I go out early and build a fire in my shop, I would also build a fire in my snorkel heater. That evening it was nice!
3. Just an FYI, it's true what you read. You need to circulate the water to heat it up. I would burn my heater for 3 hours and the water around the stove would be great. The heat would never transfer further away from the heater until I turned the pump on.
In the end, I've taken the snorkel heater out permanently and we use the 8'x8' tub as a "dipping pool" in the summer. Works great.
That being said, I'm investigating getting a stock tank, putting a coil stove underground (I live on a slope), putting the tank on top and filling up the area around the coil with gravel. The coil will be in a bricked up area to build a fire in but the gravel all around will allow (hopefully) for radiant heat traveling up. Maybe the coil can heat the water and the heat transfer from the gravel can help retain the heat. Anyone have any thoughts on that?

gcrank1
Member
# Posted: 21 Aug 2023 23:37
Reply 


Plenty of small alum fishing boats around here cheap; re-purpose one into a hot tub, most already have seats.....could even make the deck above look like a pier, lol.

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