Hi! My husband and I are very interested in utilizing the ample supply of rock in our area. We live in middle TN and we live in a limestone pit, I do believe! My husband has already built me a waterfall/fountain that turned out beautiful!! Now, I am wanting a HOT TUB! But, I want one built of the rock we have so much of around here. And, I want one that is either heated with wood or something of that nature and does not need electricity to enjoy it. The hubby thinks I'm crazy! But, I am sure, somewhere out there, someone else has done this at some time. I want something that is going to be cheap, cheap, cheap to build, run and maintain. Any suggestions?? Someone mentioned to me the other day about using solar energy...but, I believe the panels would be expensive. If anyone has any suggestions, please let me know. Thanks!

-- Rhonda Law (stircraz@concentric.net), May 04, 2000

Answers

Rhonda, if you get into the solar sites, or the old Mother Earth News, you can find plans for solar water heaters that work just fine, and wouldn't cost much to build. It would also be possible to heat the water with a wood stove that had coils. And probably, if you mortared the rocks, it would hold water all right, so I don't see any reason why it wouldn't work. BUT, would it be comfortable to relax against a stone wall? Seems like you would want river rock, or something fairly smooth, anyway. Good luck!

-- Kathleen Sanderson (stonycft@worldpath.net), May 04, 2000.

That is a good idea....as far as the relaxing on the rough rock...we plan on covering the entire inside with either a liner (poly) or with concrete. I think that should work to help that particular problem.

-- Rhonda Law (stircraz@concentric.net), May 04, 2000.

You might try to look into what is called the 'snorkel hot tub'. I know that you can buy just the snorkel part of it. What it is, is a wood fired way of heating your hot tub. It can be adapted to regular hot tubs, don't know about rock ones though. It sounds very interesting. I also agree that you need something between you and rocks though. GL, annette

-- annette (j_a_henry@yahoo.com), May 04, 2000.

Hi Rhonda,

I wish I had paid more attention to the hot tub our friends had...it was wood fired, but the tub itself was made out of wood. It was an old wine barrel (the huge kind, like they use in wineries). The thing I remember most was that it had to be fired up early in the day in order to heat the water enough by evening. We could fit four people in it.

There must be information out there. I like your idea of the hot rocks! We are now using our tub (lazy electic model) every night, and I am continually grateful that we got it. I spent hours weeding today, and can hardly move. Tomorrow morning I will get out of bed and not notice!

Best to you!

-- sheepish (rborgo@gte.net), May 04, 2000.

http://www.geocities.com/PicketFence/Garden/8784/pics/spa2.jpg Rhonda cut and paste. I highly recommend building it! Mine was built out of river rock and concrete for under 400.00. It has a snorkel wood burning stove that heats mine in about 3 hrs. The stove was the most expensive part. About 500.00 at the time but I really love it. When I'm finished I just drain the water. Anyway it was fun, easy, and could be a great family project! If I can be of help let me know....Kirk

-- Kirk Davis (kirkay@yahoo.com), May 05, 2000.

Rhonda, I think you've got the idea that wood-fired hot tubs are very possible. Be aware that a stone tub is going to syphon quite a bit of heat from the water initially. Once it gets warmed up, it will then hold the heat well. The idea comes to my furry little brain that it might be possible to build an inner hot tub, band it with hot water pipes, then build an outer wall. Hmm, a simple solar system could heat that water and even a few degrees of extra warmth in the rocks would help you heat the tub water that much faster. Hmm.

You can make a passive solar set-up to at least help preheat the water before sending it to the wood burning heater. These would be different from the more expensive electricity-generating panels. Check your library and the internet for "passive solar heat/ing". What you need could be as simple as some barrels or old water heater tanks painted black and set in the sun. A lot of black garden hose left out on the ground with water in it will heat water piping hot. But it would take a lot of hose to fill a hot tub. There are also flat solar plates you can build that either have internal piping in them, or trickle water over the collecting surface. Just do some research.

And don't forget to think about cleaning out your tub. A well-placed drain is a really, really good idea. Otherwise you'll be doing a lot of sponge work. Gerbil

-- Gerbil (ima_gerbil@hotmail.com), May 05, 2000.

Like the idea of a double wall with the tubing between the walls. I'll up the anty with this addition: instead of circulating water in the tubing, fill the tubing with vegetable oil. The veg. oil will have much higher heat carrying capacity than the water.

Whether you use solar or a heat source (fire), this system should work. If it leaks outside your tub, it's biodigradable; and inside, you got skin softner.... :)

I saw this in the book "Gaviotas: A Village to Reinvent the World." Interesting book.

j

-- j (jw_hsv@yahoo.com), May 05, 2000.

I reread my response and thought I should clarify my response.

In the book, the recirculating heated oil was used as a heat source for cooking, not for hot tub'in.

j

-- j (jw_hsv@yahoo.com), May 05, 2000.

Rhond, my inlaws copied my desing for a wood fired water heater, which I used for all my hot water needs, and used it with their "Fire View" wood stove to heat their cedar hot tub. Worked fine, except the guy who did the welding didn't do such a great job, and water started leaking into the firebox. My system utilized a double walled firebox on the woodstove. I had low pressure in my water system, so it was fine, but for their high pressure system, they took an old pressure tank and cut it to make it fit fairly close onto their Fire View (which is basically cylindrical). This was stronger, though ugly as sin, for the higher pressure they had).

I've also made solar water heater panels for under a hundred bucks. One of them would be plenty for a normal sized hot tub, but only in moderate weather. Mine aren't freeze proof. If you have enough sunshine, and want to use the hot tub in the winter (why have one, otherwise, right?), you'll want to use either the double layer mentioned above, or have a heat exchanger, (these are commercially available) to transfer the heat from a panel filled with food grade "anti freeze, propylene glycol"

You'll also want to insulate the tub very well, if you don't want to burn tons of wood. I don't know what you're going to do about jets, though.

JOJ

-- jumpoff joe (jumpoff@echoweb.net), May 05, 2000.

Now I know this sounds rather simplistic compared to everyone elses Ideas, but I am thinking one could build a simple rock tub with a rock formed oven attached. The oven could be similar to one built to bake bread in with a smoke chiminey rising well above the tub. If the back wall of the oven was the tub wouldn't simple heat transfer raise the temperature of the water. You would want to make sure that the oven had a damper to control the heat. If the tub was put under a gazebo it would probably look quite lovely. You might even bake bread while you took a hot soak. Also it would be necessary to add a way to drain the tub for cleaning. Just thinking, on paper.

Little Bit Farm

-- Little bit Farm (littlebit@calinet.com), May 05, 2000.

Now I know this sounds rather simplistic compared to everyone elses Ideas, but I am thinking one could build a simple rock tub with a rock formed oven attached.

Oh my gosh!!! That is wonderful!!! That way, I wouldn't have to buy that expensive stove....we could, in reality, BUILD ONE of stone ourselves and save that money!! What a great idea. Everyone's ideas have been wonderful and we truly thank you all for your input. The more ideas we get, the more real our hot tub becomes. Thanks guys and keep the ideas coming!! :-) Rhonda

-- Rhonda Law (stircraz@concentric.net), May 06, 2000.

Rhonda: Beware because some rocks blow up when come in contact with fire. If you Build a stove with stone make sure you use the right ones. Also concrete inside my spa has 2 coats thoroseal and 2 coats UGL swimming pool paint. Works fine on bare skin and waterproofs. Hope you do it......Kirk

-- Kirk Davis (kirkay@yahoo.com), May 07, 2000.

The rocks that will blow up when they are heated by a fire have usually been sitting in water for a while and absorbed some moisture. That is why, when building a stone firepit for a campfire, you should never take the rocks out of a creek or other body of water. Otherwise, I don't think you need to worry about it too much - - I hope!!

-- Kathleen Sanderson (stonycft@worldpath.net), May 07, 2000.

'The Book of Masonry Stoves' by David Lyle has some diagrams of how the roman baths were heated. It's a great book for anyone building any kind of masonry heating thing.

Good Luck

-- Rod Perrino (redjouster@aol.com), May 08, 2000.