Thumper style hot tub?

[shane_o_ca]

I was recently at my friend's cabin, and he was thinking of making a wood fired hot tub. He was discussing ways of heating the water etc, when I remembered how a thumper still works. Got me to wondering if you could make it work for an outdoor, wood fire hot tub. Basically the water would be heated in a tank with a copper pipe out the top leading to the bottom of the hot tub. The steam would then heat the hot tub water, and create bubbles. You would have to create a false bottom in the tub so the copper pipe wouldn't burn you. I'm just wondering if the steam bubbles would scald a person. Could be an interesting idea...

[Prairiepiss]

It could be possible for the seem to scald someone. I don't know how likely it is. But there are many designs out there for wood fired hot tubs. Most heat the water and circulate it. I don't know if I like the steam idea.

[maheel]

just get a pump and run a copper "coil" into your hot fire tank and then back into the hot "spa" tank

when it's hot enough turn the pump of for a while, then back on again later etc

you dont have any "pressure" vessels then to worry about

you could use a beer keg with the top cut off full of water on the fire and chuck the coil in that
it's not going to rust etc when you not using it

but it might take a while to heat up a big tub ?

[Dnderhead]

you dont need the pump, just the coil in fire, hook coil to top of tub below water line ,other end to bottom of tub.

[Prairiepiss]

Dnderheads idea is the most common. Just using natural convection to circulate the water and heat. The ones I have seen used a tank with a pipe from the bottom of the tub to the bottom of the tank. And a pipe from the top of the tank over to the tub at or above the hight of the tank. When the water in the tank is heated it flows up and out the top pipe and draws cooler water in the bottom pipe.

[Dnderhead]

that is the way that waters was attached to wood/coal stoves/furnaces.

[The Baker]

Dnderheads idea is the most common. Just using natural convection to circulate the water and heat. The ones I have seen used a tank with a pipe from the bottom of the tub to the bottom of the tank. And a pipe from the top of the tank over to the tub at or above the hight of the tank. When the water in the tank is heated it flows up and out the top pipe and draws cooler water in the bottom pipe.

As you probably know the traditional bath in Japan is very hot; so hot that it can be painful even to move in the water.
One soaps and washes oneself before entering the bath, so that the water remains clean and can be used by the whole family.
The water is so deep that one can kneel and be covered to the neck; the big deal is to soak for a while in the hot water and relax away the cares of the day.
When we stayed with a friend in an oldish farm house in Japan they heated their bath with a wood fire which was below the level of the bath and stoked from the outside; and when father had put some more wood on the fire it became almost unbearable!

[maheel]

Dnderheads idea is the most common. Just using natural convection to circulate the water and heat. The ones I have seen used a tank with a pipe from the bottom of the tub to the bottom of the tank. And a pipe from the top of the tank over to the tub at or above the hight of the tank. When the water in the tank is heated it flows up and out the top pipe and draws cooler water in the bottom pipe.

out of interest will this work if the fire and tub are on different levels ? (significant @ say 3 feet or more)

if pump was to be used put it on the "cold in" side pushing water into heat so pump does not get super hot...

[Dnderhead]

the tub/tank shuld be the same height or higher than coil.

[Prairiepiss]

As ling as the heating aperatice is at or below the water level of the tub it should work. If not you can't get the natural flow of hot water. Heat rises. You could use a pump. But I don't think you would get as much heat transfer as natural. I could be wrong about that? Plus you would be using unneeded energy for the pump. Let the heat work for you.

[shane_o_ca]

Yeah we were talking about conventional ways of heating it, but I was trying to come up with a way that you could have bubbles as well. It might take a while to heat up this way, but the bubbles would be a nice touch.

[Prairiepiss]

I think I would come up with something other than steam. Or a way to make sure the steam wouldn't scald someone. And you would be dealing with a little more pressure then a thumper to make it bubble. So that could be a concern to.