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wood fired hot tub heater

 
                          
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Well this year I wanted to try something different instead of using the pump to circulate water through the copper tubing method. I wanted to build a thermosyphon unit. This one won't be sealed so it will be critical as to the positioning of the barrel next to the tub.

I have had this  [Wood-fired Canner] for years now. http://www.lehmans.com/store/Kitchen___Canning_and_Preserving___Canners_and_Cookers___Wood_fired_Canner___32185?Args=

So I modified it using 11/2'' thru-hull boat fittings. Will do the same with the hot tub.




Here is the free hot tub I got last year.

 
                          
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I got the thru-hull boat fitings mounted in the tub.


I also have an idea to shrink the amount of water in the tank so it would heat up faster. The outside dia. of a plastic 55gal drum is about 2'' smaller, so if I cut it to fit inside with 4'' of space off the bottom that should do the trick. Just bolting it around the top lip to keep it in-place. I also have a stainless lid that came with this but it just lays on top. It would be nice to have a sealed lid for it.
 
                          
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Well I leveled  the tank and lowered it just need to make the lid watertight. It is positioned 2 feet from the tub.
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Next the lid and fill it up to see if the lid will leak or not.
 
                          
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Got it filled this evening used a pc. of 3/4 ply to give even pressure to the stainless lid that came with this wood fired canner. The ratchet straps work for now. The pc of galv. pipe is for a heat shield because the strap on the back is kind of close to the stove pipe.


A pic. with the door open.

The water temp is 60 and after 45min. burn the outlet temp from the top hose is 90 and a good circulation is visible in the hot tub.
 
tel jetson
steward
Posts: 3338
Location: woodland, washington
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nice work.  any idea how much wood and time it will take to have a nice, warm soak?

I've seen a similar setup to heat a cattle trough for a hot tub.  never saw it in operation, but it looked nice.

quick thought: is there room in your burn chamber for some fire brick around the outside and bottom?  could make for a hotter, more efficient burn.
 
                          
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It doesn't take but 3-4 splits of wood to keep this tube cooking every day to about 105-110 deg. I really need a good insulated cover for it.

When the heater is putting out the heat I can actually feel a suction from the bottom fitting.

I have some stainless angel pcs. I need to weld on to try and stop the seepage from under the lid.
Will post pics. when I have that part done.
 
                          
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I finally welded 8 brackets around the top edge for hold downs and the leaking seems to have stopped.
When the fire is going I can really feel the suction on the bottom hose in the tub, the theromosyphone works great.
 
                    
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What if your water gets too hot & you want to cool it down, is there a way to do that? D
 
                          
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No way to drop temp very quickly, just takes some getting used to how much wood to burn to gain the temp needed.
Added a feature to get more out of the smoke?
 
                    
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Oh I see, I suppoze you could just add some cold from the hose? or is volume a touchy thing?

So what is that BBQ looking thing in the picture? A steam valve? Or is it just your chimney top, is there a reason you use that shape?  D
 
                          
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The tub will loose temp each day. As far as volume once it is full ,if no leaks, don't add water it changes the ph etc.

The cheap grill I had I cut a 6'' hole in the bottom and slide it over the flew pipe and it becomes a smoker.
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So you can smoke a  brisket while you hot tub, pretty cool & very cleaver.

How do you keep the water sanitary?

D
 
                          
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Dianne Keast wrote:
How do you keep the water sanitary?

D


Hot Tub Water Chemistry
http://www.poolspaforum.com/forum/index.php?s=e6c682801f42d2a70feb36ac7e120d93&showforum=13
 
                    
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Thanks so much for sharing this cool stuff!

So keeping the water sanitary is basically the same for this tub as for any other?
 
                          
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Yea Dianne
All one needs is a sealed stainless steel container to build a fire around, or under in my case, and heat up the water without electricity.

Here is a heater that is commercially sold which has a water-jacket surrounding the fire box.
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This makes me want to get a hot tub! thanks again D
 
                          
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Finaly got a cover for it off craigs-list... had to build up a frame arround it from lumber off craigs-list..
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