Pizza Oven Hot Tub

[Rochottub]

Im just starting a design for a pizza oven heated hot tub, ideally portable.
I've never built an oven but I'm handy and know masonry and furnaces.
I'd like it to operate by thermo siphon without gas or electric.
ideally able to cook 2-3 16" pizzas and heat a 6-8 person tub.

I thought heat exchange would occur both directly through the back stone wall and by running copper coils between inner and outer dome

any references or thoughts?
I'd also like to be able to stick a hatch ontop of the tub and convert it to a sauna

[david s]

I have similar plans, but not sure I’ll ever get around to building it. Because the water in the tub will be acting as a heat sink it will be sapping the oven of heat, so I think it’s optimistic to expect to attain and maintain pizza temperature, but I should think you could probably roast and bake in it. My idea was not to cook in it but just to use the inner chamber as a fire box. A cast form, with a ferrocement shell sitting on top to form the hot tub. I think a thin vermicrete gasket between oven chamber and hot tub would be required to cope with the expansion of the inner chamber so it wouldn’t crack the tub, would be mandatory. This would also take the sting out of the heat before it hits the hot tub.

[UtahBeehiver]

This will be interesting to watch. Any way to take advantage of flue heat vs dome heat? Flue heat is wasted heat that could be used for a heat exchange coil.

[SableSprings]

Welcome Rochottub! Off the grid in B.C. Canada,our friends wanted to have a hot tub. He found an aluminum hot tub with a wood fired heating box for just what he wanted. It has been installed for several years now and works well with these caveats...1) takes a really long time to heat up, 2) water circulation for the heat is poor (heat pools at top), 3) if you overheat, it is difficult to bring the temp down. Currently, we build the fire and periodically literately stir the pot to break up the hot/cold layers of water that form. Takes about 4-5 hours to come to temp when the water is warm from the previous day and much longer to bring it up from the initial cold lake water fill. Because we actually build a fire "in the hot tub" and it takes such a long time to come to temp, I'm not sure heating 300-400 gallons of water from an external WFO connection is going to be worth the effort. That said, it is nice to have the opportunity to sit in the hot tub while out in the wilderness. I've attached a couple pictures for your entertainment...and a bonus picture of my surprised friend in a dry tub. I've attached a link to the Alumi-Tub web site.

http://alumitubs.com/

p.s. If you do try to use a heat exchange coil, make sure you separate it from the actual oven flue exhaust. My friend uses a copper coil that lies inside a wood fired stove chimney to heat house water and the creosote buildup on that pipe is incredibly quick and thick (colder copper pipe with water flowing through condenses the creosote very effectively )

[SableSprings]

Here's another couple of pics of the wood fired hot tub area. Note the extra tall chimney stacks...needed to get the smoke from the hot tub above the sitting area of the deck and taller stack (partly hidden by the trees) on the nearby WFO (The Big O - orange-ish dome on right of hot tub deck, second pic).