Rocket heater for a Hot Tub..?

Hi everyone. Any ideas here..
Been doing some research on this, and Google et al have come up with nil so was wondering if any of the more experienced rocket builders on here have some thoughts.

I want to convert the old fishpond outside - cats keep eating the fish anyway and for the sake of growing watercress not worth it - into an outdoor hot tub.
I figure in the miserable UK weather I could do no worse than having somewhere to relax after working in the garden and in miserable weather.

I have a mental image of what it would look like, but have absolutely no idea if I am off with the pixies on this one or not.

The fish pond is raised 3/4 meter high above ground, strong face brick build and around 2,5m x 4m oblong with a pond liner inside, surrounds filled with soil and plants etc.
I am thinking of emptying it all out to a brick shell, and building a rocket stove heater next to the shell outside, punching a hole in the shell wall and creating the seating within the shell which would encase the exhaust pipe. Have tried to attach pic of pond so hope it comes thru.

This would then be a warm seat all round the "tub" which would heat the water! I could not use cob obviously, so thinking non-eco cement which is then painted with a rubberised watertight sealant. Think swimming pool here.

But would it work?
There are going to be 4 bends here, concrete instead of cob, and a whole lot of water and possible bad sealing or seepage issues into concrete and pipes.

Of course would like the stove to be functional as well, may as well have a bit of a hot area to stick a pot of mulled wine on to heat, or cook something on whilst relaxing, and it needs to look decent in the garden.

Weather resistent for the actual stove? Can I encase the entire project once proved drawing correctly etc in weather resistent plaster of cement?

Would really appreciate any comments or thoughts here.
thanks
Trish

trish,
you could try a search for "snorkel" stoves, also try contacting this fellow in Bristol http://www.youtube.com/watch?v=GHOSRmcM4as

My idea for an outdoor hot tub is based on a design from Roman times--I'm sure it has a name, but I'll just call it a Roman bath. The tub is connected by two pipes to a smaller tank, which is over a rocket stove (not a rocket mass heater, just the basic rocket stove). One of the pipes is at the bottom of the tub and the other is at the top. As the water in the tank is heated, the hot water pushes out the top pipe into the tub, where it cools and sinks and is drawn out by the bottom pipe back to the tank to be re-heated again. I drew a very basic graphic to illustrate.

Galadriel Freden wrote:My idea for an outdoor hot tub is based on a design from Roman times--I'm sure it has a name, but I'll just call it a Roman bath. The tub is connected by two pipes to a smaller tank, which is over a rocket stove (not a rocket mass heater, just the basic rocket stove). One of the pipes is at the bottom of the tub and the other is at the top. As the water in the tank is heated, the hot water pushes out the top pipe into the tub, where it cools and sinks and is drawn out by the bottom pipe back to the tank to be re-heated again. I drew a very basic graphic to illustrate.

looks like the principle of a Dutch Tub you got there Galadriel. The diff is a coil of pipe surrounding the fire basket ( flue or tank area can be used) which will act as a heat exchange draging the cold water from bottom of tub and pushing out the top.

I considered this, neat and compact and a closed unit for water, but wanted something more efficient and putting the heat into the actual tub in addition to the heat exchange via coil. Since i need to build seating in the pond, figured may as well do it in conjunction.

Andor Horvath wrote:trish,
you could try a search for "snorkel" stoves, also try contacting this fellow in Bristol http://www.youtube.com/watch?v=GHOSRmcM4as

Wow, that looks pretty good, thanks for link Andor.
that should heat the water fast and pump it back into the tub.

So do you think trying to feed heat into the tub via the bench / seat that will go round is not a good idea - just pipe it in an out near the fire box? thought i may be onto something , creating heated benches in the tub

This company shows a diagram similar to the drawing by Galadriel.
http://www.islandhottub.com/index.html