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how do i make a wood fired water heater? Answered


Are you using it indoors or out ?

For indoors the older wood stoves had a steel reservoir chamber with a small relief valve attached to the side of the stove and a spigot which could also be attached to a pipe to the sink.

Thermal siphon will move warm water through the line as cold enters.

You can also wrap copper tubing around a wood stove pipe and it will absorb the heat .

For outdoors you can use any small steel tank or old water heater tank with a pressure relief valve and I see these made from old propane bottles all the time and used to heat hot tubs.

The heat source can be wood placed in a fire pit under the tank and it doesn't take much to heat up small quantities of water prefer solar hot water and a simple batch water heater is just an old water heater tank painted flat black enclosed in an open top box with a sheet of single pane glass covering it.

Placed in the sun these heat up fast and as cool water enters warm water is pushed through the pipe to the house or you can use a small inline pump.

For more ideas on solar hot water and solar and wind power visit my website:



Re-Design's link is a good example of what you can do, but I would suggest using steel pipe rather than copper. Replace the pool with a non-pressurised tank in the roof-space, it'll help to have a head of water on this. Use the pump to draw down to the fire rather than pull up.


It SHOULD just convect, with a lttle bit of care with the pipes.


Yes I was thinking about that, but in the end I thought the pump would add some reliability (vapour-locks, steam generation etc)


....the idea is that there should only be a thermosyphon: if the power goes, there's no flow path to the tank and you coil melts. It won't go boom, granted, because the other end is still open.

I've played with small thermosyphons, got 'em to work but on the cheap-coffee-machine principle of steam-driven spurts. I see it working, but making disconcerting noises and humidity. However, with a good head of water it might work better?


...its how the standard hot water systems here have always worked !


Most heating systems I've known have included pumps. OK they are running central-heating loops, and I've seen heat-exchange tanks, and systems clogged-up-to non-functionality with 'oxide... But the principle is sound, my only thinking on the pump was that I didn't know what impro' pipework might be added, otherwise I agree on how these things ought to work.


Here is an instructable to get you started.

REalize that this and probably any heater you make will not pass inspection of the building inspector and will void your home fire and accident insurance.

This one does not use a tank and that makes it saver.  A tank water heater is inherently dangerous unless you build in the safeguards to prevent over pressure causing an explosion.

Good luck.

In the UK the hotwater tank is usually vented, and usually upstairs - there are very specific safety regs for unvented tanks. Convection heats the tank very well.