Wood fire coil kit  (heats water through gravity-fed convection, no power, no pump)
 
Got a tub/tank/bath sitting around and fancy turning into an off-grid wood fired hot tub? This is the solution for you! Unbox and connect the coil in less than 30 minutes.
 
Includes
- Stainless steel coil
- Heat resistant tubes
- Quick connectors
- Hose clamps
 
Where it can, and can't, go
The wood fire coil kit produces an open fire while in use. The tub must be placed on a non-combustible surface: compacted cracker dust, gravel, concrete, stone pavers, natural earth, or slate. It cannot be placed on a timber deck, composite decking, artificial turf, or any combustible surface. See the Setup section below for fire-clearance distances.
 
How do I control the temperature?
The fire is your control lever. Keep a steady burn and the water heats gradually.
When you're about five to ten degrees off your ideal temperature, stop adding logs and let the fire die down.
As the flames fade, the heating slows and stops on its own.
Every tub comes with a floating thermometer so you can keep an eye on it.
If you overshoot, a bucket of cool water topped in brings it back down quickly.
In short: add wood to heat, let it burn out to stop.
 
How It Works
People have heated water with fire for thousands of years. We've just made it comfortable.
 
1. Fill it. 
2. Light it. Build your fire inside the coil. Water flows out of the tub, through the coil, and back in warmer. Hot water rises, cool water follows behind it. No pump, no power point, no moving parts. The fire moves the water by physics.
3. Soak. About 90 minutes to 38°C. Light it, pour a drink, watch the steam start to curl. By the time it's ready, so are you.
When you're done, let the fire burn down and it cools off on its own. Drain it onto the garden, no chemicals to worry about.