Wood Fired Hot Tub?

So I saw this kooky photo and it got me thinkin'...  How could one create a real outdoor wood fired hot tub?  Because this thing is NOT real.  Photo edit o rama.

But the concept is really kewl.

Our wood fired hot tub  has been a real luxury and quality of life improvement for us!  We got one of the smaller ovular tubs and it’s ideal for a couple, any larger would just take longer to heat. It takes about 2-2.5hrs to heat with our Chofu stove/water heater, and one could use a propane adaptor if desired. To offset the carbon footprint, I gather wood from local forest service burn piles that would be burned anyway. I have also buried the equivalent of hundreds of cords of wood (though it wasn’t firewood, it was brush and rotten logs), in hugels. I also find we are perfectly comfortable in a 60F house when we’ve just gotten out of a 110F tub, so we forego heating (with wood) the house quite a bit when we do a hot tub. As for water use, we generally use it during the wet season (115” last year), and if it’s at all dry out we water acid loving plants  with it. I think the cedar scented water helps make us less appealing to ticks and mosquitos.

It is hard to beat watching a meteor shower or moonrise over the mountains in a cedar hot tub!

When I was a kid my cousins had one that was just an old bathtub up on blocks with a fire under it.

We'd get four kids in there and have contests on who could hold their breath longer. One of my cousin's friends was holding their breath way longer than anyone else. We finally figured out he was breathing the air from a bubbler they had coming in the overflow drain.

I think I have seen a model where the wood heater is inside the tub.

John has the right idea:



source

https://permies.com/t/49111/Rocket-hot-tub-skids-Wheaton

John C Daley wrote:I think I have seen a model where the wood heater is inside the tub.

Howdy,
Friends of mine have a round wooden hot tub with the wood stove in the tub.  I have an old cast iron tub that I can just build a fire under or around it to make it HOT! I am going to put it on skids so I can move it into different places. Lots of small dia. sticks to burn, so move tub to the piles.

Both internal and external heaters have their upsides and downsides. Both can be dangerous if water level is to low. Internal ones can be damaged by overflow into the firebox as well though. We went with external because it fit our space and has less likelihood of a user burning themselves touching the chimney, which is within reach of a wobbly bather with most internal ones. My wife and I were very interested in Kiwi Tub’s design, but he understandably doesn’t ship to the US. Still worth checking out for the design ideas alone:

http://kiwitub.co.nz/

I've been in a couple of the internal submersible type and they've always been plenty hot.

As for external, this sort of thing plus a circulating pump might work good for a hot tub: