Introduction: Wood Fired Steam Bath
This is a steam room I built in the backyard which was inspired by the steam room at the Confest festival in Australia. It uses a wood fire to heat copper pipe carrying water. The water in the pipe boils and produces steam which is blown out the top end of the pipe into the steam room. Any (liquid) water that is blown out the steam pipe is recycled back into the resoirvoir, to conserve heat and run more efficiently.
This instructable won't cover the construction of the steam room itself, just the boiler and steamer component. The steam room for this project is approximately 1.8m x 1.8m x 2.0m high and is constructed with a pine frame and double wrapped with greenhouse plastic - on the inside and outside of the frame.
Step 1: Make the Fire Chamber in a 44 Gallon Drum
THE DRUM: Take an old 44 gallon drum and cut a hole in it to fit a 24 inch bicycle rim. The rim was bent to match the round profile of the drum. It was also cut at the rim join so that it could be flexed into the drum hole and then sprung back into it. It required no fixing. I put the rim in because the edges of the hole were sharp and jagged, having been cut with an angle grinder. Perhaps a cleaner cut and finish of the hole would forego the need for the rim. However, I also like the look of it.
FIRE PIT: Put a Weber barbeque pit in the bottom of the drum. I sat it on top of a steel pot to raise it off the floor and allow more airflow from underneath through the fire.
LID AND FLUE: After fitting the copper pipe (see following steps), put the lid on the 44 gallon drum and attach a flue coming out of the lid. You could have it without a lid, but having a lid on with the flue conserves heat in the drum which delivers more of the heat from the fire to the pipe. The flue on my drum could be larger, but it's just what I had lying around at the time.
Step 2: Make the Boiler With Coiled Copper Pipe
MATERIALS: Because I was using materials that were lying around my workshop, I ended up with two lengths of copper pipe of different sizes - roughly 2 to 3 metres in length each - and coiled them manually. *Update* I rebuilt the boiler recently and replaced the two lengths of copper pipe with one long 18m piece, however this did not work well at all! The pressure created in the pipe from the heat was not enough to blow the steam out through that long length of pipe. Instead the hot water simply bubbled back through the water reservoir, which didn't produce much steam. So I ended up cutting that one long pipe into three sections of 6m each, so had three separate water inlets and steam outlets. This works brilliantly, with only a small fire required to produce an awesome hot steam room!
SHAPING THE PIPE: You will need to straighten out a length of the copper pipe at each end of the coil - long enough to reach out of the drum, through the heat shield and into the steam room. If these straight ends are too long, then it may be difficult to fit the pipe all at once inside the drum and through the holes. It may be easier to straighten the pipe as you feed it out of the drum.
EXTENSIONS: An optional way to do this is to braze extensions to the pipe outside the drum, particularly if you want the fire further from the steam room. I didn't have the tools or skills (or need) for this so just fitted the complete pipe all the way through.
SUPPORT: In my boiler, the copper coils simply hang there above the fire pit, being supported only by the straight sections which sit in the holes in the drum, heat shield and steam room frame. The case may be different for the longer length of pipe which I've suggested here, which will be heavier and may require support. This support could be as simple as a steel rod skewered through the drum which the coils rest on.
INSULATION: Given the steam room is wrapped in plastic and is close to the drum which gets very hot, it required a heat shield - a piece of corrugated iron. I also put insulation around the copper pipe as it enters and exits the framework.
Step 3: Seal the Pipe Into the Water Reservoir With Silicon
WATER RESERVOIR: The water reservoir was made from a 4 Litre steel vegetable oil tin. I ended up painting this one because the original one rusted through after a few months of use. You will need to drill holes through the tin for the copper pipe ends, one end positioned high (the steam outlet) and one end low (the water intake). In my design these are spaced 20cm apart.
The tin should be screwed into the steam room framework to support it.
SEAL WITH SILICON: Smear silicon sealant around where the pipe enters through the holes, to make it hold water. I originally wondered if the silicon would stand up to the heat in the pipe, but it has never been a problem, provided the system never runs dry.
Admittedly, this is very rudimentary, and ideally would have the pipe brazed into the reservoir. However, it does the job reliably!
Step 4: Fill to Just Below the Steam Outlet Pipe at the Top
Once the silicon has cured, fill the tin with water to just below the steam outlet pipe. There won't be much steam produced if that pipe is covered by water.
Light the fire and see how it goes. It usually takes about 10 minutes from lighting the fire to having a good hot steam room. Bring a small bucket of water into the steam room with you and keep refilling the reservoir every 10-20 minutes.
CAUTION: The steam coming out is, of course, very hot, so don't get too close. Make some sort of guard over it if you think it will be a hazard to someone.
After it has been running for a while and recycling the hot water coming out of the steam pipe, the water in the reservoir will be hot before it even gets to the coils above the fire. This greatly increases the rate at which steam is produced.