I wanted to make an upgraded version of the "build a fire under the tub" hippie/cowboy bath experience. I put a woodstove with the top removed under the tub, sealed it with cob, and put a simple thermosiphon heat exchanger on the chimney to heat a shower, too. It takes about 30 min to heat up the tub and then will stay hot for a couple hours just with the coals or as long as you keep adding wood.
I used all free, salvaged parts except for $50 in copper tubing and some lumber that I milled.
I'm hoping to post another step-by-step video of how I built it, but here are the basics:
- rock foundation
- wood frame under the rim of the tub
- metal heat shield around the stove to protect the wood members
- thermosiphon copper tubing heats an old water heater tank for the shower
- wood plank to sit on so you don't burn your butt
- I found an wood stove that was bolted together to make it easy to take the top off
- I sealed the gap between the top of the stove and the bottom of the tub with cob on a chicken wire mesh
- I built it on a slope so the deck to get in the tub is at normal height and you go down below to stoke the stove
- the shower takes longer to heat than the tub but stays hot for hours because I super insulated the storage tank
