Rocket stove to heat hot tub ?

Hi, Tacoma area permaculture friends,

Just got the word from Kelda that we have this neat forum page for our own group's discussion topics.  I thought I'd kick it off with my current mind bender!  I just got a hot tub ($300 off craigslist!).  I'd like to be as sustainable as possible with it.  I do have those roof-top solar water heater panels, but I don't really have good southern exposure to use that for the tub.  So I was thinking about a rocket stove/mass heater but I'm having trouble figuring out the "plumbing"!  There is a great thread on one of the other Forums here about a guy who used an old woodfire heated canner to heat his tub but those suckers are expensive!  As are the double jacketed stoves designed for hot tubs.

So here's the challenge:  I know (from Paul's videos and site visits) how to heat cob benches.  And I think there was a setup at Bullocks' in the classroom space that was a cookstove, room heater AND water heater, but I didn't look at how that was set up.  I'd like to combine several uses for this one too.  Anyone want to join me in a brainstorming session online (or in person) for this?

There will definitely be a party to celebrate the successful completion of this project!   Oh, and my BF in Olympia also picked up an old hot tub so we'll have a second chance to build one for him.  Usually, we do a project at his place to "learn how" and then I get the perfected product but I thought we'd work on my place first since there's more room in my backyard.

Thanks for all the great ideas that I know will be coming!
Patricia

Ditto pretty cool that there is now have a forum on permies dedicated to Tacoma. It almost looks like we succeeded from the Cascadia group. I'll post more often then I have in the past and maybe even outside of the Tacoma forum. *gasp*
but about that hot tub.
Here are my three suggestions for consideration.

[li]Compost heating[/li]
Using some sort of pile built around some brass or metal tubing. The pile would need occasional maintenance I'd imagine around once every couple of months if stacked right and more often in the more finicky early days. The biggest problem I actually see with this is the water getting too hot A good hot tub should be around 104F and never over 110F. I have seen compost piles used to heat water in the past with scalding results not desirable for a hot tub. So if you could somehow regulate the system by taking heat out of the system with some sort of sensor/blowoff/ or heat exchanger, as hot tubs primarily use ambient temperature while cutting to heat pump to serve as the regulating function, if you could figure an alternative you'd be sitting very comfortable with a low energy hot tub.
[li]Geothermal with lift pump[/li]
Another option that might provide some fruitful results, is a geothermal option. Ideally this would be bundled with a geothermal system that provided heat exchange for a house but it would work by keeping the water constantly around 55F, the constant temperature of the earth near the surface, then using a standard hot tub heater to life it the other 50F.
[li]The stove[/li] is another viable option; however, it's probably the one I am least qualified to give advice on, but on this forum I bet there is someone who--

Hi Patricia-
I'm not from Tacoma, but am very interested in this topic.  I see free hot tubs on Craigslist about once a month and have more wood than I can ever use.  I would love  to build a rocket stove heated hot tub.  Keep me posted on this if you guys have any successes (or failures) with this.

Great idea