Crazy idea? Outdoor wood heat spa?

[Kingcreek]

I've had this idea for awhile but I'm getting closer. I want a combo hot tub and traditional sauna behind my house. Stand alone structure close enough to the backdoor for convenience but far enough for fire safety. I live very happily rural and NO codes or building permit issues. I want a thermosyphon system entirely wood heat. I have better than average homeowner construction skills and average welding skills. Water is no problem but would rather not have electric if possible. I'm thinking outside wood feed to a firebox in a dividing wall with hot rock box on the sauna side and some kind of waterjacket heat exchange for the tub side. Possibly 3 compartments, one for the tub, a small dressing/rinsing area that would connect to both the sauna and tub area. Big enough for 4. Total footprint 10x12or maybe less.
I've seen wood fired tubs (ie snorkel etc) and I have plans somewhere for a traditional wood fired sauna but I'm struggling with the marriage of the 2 with one firebox. I'm sketching some things up but it's not coming together. Maybe a glass of single malt and a fire in the fireplace will help tonight.
Any thoughts or knowledge of similar? My internet searching is limited to my iPhone and a poor connection until I'm at work tomorrow.
Maybe should have gone to the other forum but Thanks

[vaskidmark]

Scandawegians and Rooskies have set-ups like you describe.  Sounds like it's a choice between checking out the bikini team or heavyweight power lifters for pictures to see which design you like better.

I know where you can get a good deal on birch twigs, but you will be on your own for a snowbank/frozen pool.

stay safe.

[cassandra and sara's daddy]

Whatever you decide I would love to see how it works out I have an existing slab crying out for something like that


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[Kingcreek]

I really want something for weekends. Wood fuel means some planning ie 3-4 hours lead time. I can drain water when done, no pool chems or anything. I have a 200 gal propane tank I can incorporate into a waterjacket, cut and weld a firebox and flue into it. I'm trying to figure out how to have control over 2 environments, one dry and one water but both from 1 heat source.

[K Frame]

Put the woodstove with a waterheating jacket in the sauna, and locate the spa above the level of the woodstove so that you get the whole gravity thing going on.

The key to doing this properly is to make sure that your pipes are sized correctly.

[charby]

I remember seeing something like what you mentioned in the back of a Mother Earth News magazine.

[K Frame]

Here's a good primer article...

http://www.fastonline.org/CD3WD_40/JF/JF_OTHER/SMALL/How%20to%20build%20a%20safe,%20effective%20wood-fired%20hot%20water%20heater....pdf

[Kingcreek]

I remember seeing something like what you mentioned in the back of a Mother Earth News magazine.

That tub is almost certainly a Snorkel. I've looked into them.
I like that but I hope to have the hot tub and sauna under the same roof and sharing the same wood heat source. A firebox/waterjacket for the hot tub with an extension into the sauna for the hot rocks box.

[Firethorn]

That tub is almost certainly a Snorkel. I've looked into them.
I like that but I hope to have the hot tub and sauna under the same roof and sharing the same wood heat source. A firebox/waterjacket for the hot tub with an extension into the sauna for the hot rocks box.

I think it'd tend to be the opposite - pipes to the hot tub, fire beside/next to the sauna.

It becomes complicated because the sauna is presumably hotter than the hot tub, but lower thermal demand(it's 'just' air).  The hot tub is lower temperature, but requires more heat.

I'm thinking setting the fire underneath the hot rock box so you get maximum temperature there, with a water jacket on the exhaust pulling heat out of the chimney for the hot tub.

[cassandra and sara's daddy]

Rocket stove under the sauna ?


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[K Frame]

You do realize that thermosyphoning doesn't really work laterally, right?

[Firethorn]

Rocket stove under the sauna ?

A couple of these might actually be simpler and more efficient than trying for a single firebox.

[KD5NRH]

A couple of these might actually be simpler and more efficient than trying for a single firebox.

Yup; sounds like the ideal setup would be something like a Rocket Mass Heater with the barrel in the sauna and a liquid thermal mass.  Obviously you'd need a watertight flue, but it should work.

[Kingcreek]

2 firebox heat sources might be easier to engineer and I s'pose tending 2 fires in near proximity is no more trouble than one. Just means 2 smoke stacks on a small structure. welding up a stand alone sauna hot box would be much easier than any combo with waterjacket.
The snorkel hot tubs aren't cheap but look pretty nice.
http://snorkel.com/hot-tub-products/wood-fired-hot-tubs.php