Convert an Old Gas Water Heater to a Wood Burning Boiler

Convert an old gas water heater to make a do-it-yourself boiler to warm your domestic water. The woodburning water heater works like an outsized teakettle to warm the water and costs less than the power company charges.


| September/October 1982



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The heart of our do-it-yourself boiler is, understandably enough, a salvaged gas-fired water heater.


PHOTO: MOTHER EARTH NEWS STAFF

Convert an old gas water heater to a wood burning boiler to warm your domestic water and a corner of your home, too! 

When it comes to energy use, a little common sense can go a long way. Consider, for example, the water heater in your home. Whether it's gas-fired or electric, chances are the unit periodically spends its time brewing and re-brewing a 30-gallon (or larger) batch of "tea" . . . which might be heated several times before the first drop is used. However convenient such an arrangement may be, though, it's anything but economical.

Of course, there are timers available that can limit the frequency of such an appliance's on/off cycles — -thus reducing energy consumption — but there's another alternative that might be worth considering: convert an old gas water heater — a woodburning water heater — which, of course, warms your domestic water only when you stoke up its firebox.

If you were to price one of these outsized teakettles, you'd discover that a well-built commercial model could set you back $160 or more. And that's precisely why we poked around in our local scrapyard to come up with enough "junk" to construct a homebuilt water warmer . . . for less than 10% of the going rate.

The heart of our do-it-yourself boiler is, understandably enough, a salvaged gas-fired water heater . . . which is perfect for this project because [1] it was designed to heat and store liquid in the first place and so already has a glass lining, pressure-tested seams, and an insulative jacket . . . [2] it has a central flue column, which can be attached to a length of 3 inch stovepipe and thus connected to an outside chimney . . . and [3] it's inexpensive — or, if you're lucky, free for the hauling — because dumps and junkyards are sometimes littered with units having faulty burners or thermostats but perfectly good tanks and jackets.

In addition to its holding tank, our do-it-yourself water heater needed a firebox . . . which we made from a 35-pound grease drum cut down to 20 inch in height. After trimming out a 7-1/2 inch by 9 inch hole — beginning at a point 4 inches up from the bottom edge — in the side of the container (we used a saber saw rather than a torch, because any grease left in such a barrel could be volatile), we cut a piece of 24-gauge sheet metal to 8-1/2 inch by 11 inch and used the side of the grease canister to form the plate into a curved shape.





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