Hot Water Tank Conversion : LUSENET : Countryside : One Thread

Does anyone know how to convert a gas hot water heater to one that is heated by wood? (Firebox under the tank instead of gas flame) Natural gas prices are so high here I'm looking to convert. I don't have a wood stove installed that I can run lines to. HELP.

-- Deborah (, April 13, 2001


I have seen several of these work, and all they are is a box built from firebrick with the tank from a hot water heater on top.You can have the tank stand up or lying on it's side. As far as converting goes, you need to figure out if you are trying to keep the tank hooked up to the regular water supply for the pressure; I guess you would have to experiment with how big a fire would keep hot water pumping out while tank refills with cold.(Any plumbers here?) I do know that you must make sure to maintain a pressure relief valve so that the tank will not blow up when heated. The simple ones that I have seen are the tank is removed from the hot water heater assembly,set on the fire brick box, and a fire built underneath. This is usually located outside in a funky plumbing set up, piped from there to house.I do not think the metal gas flame area of a regular water heater could take a wood fire, nor the insulation around the tank inside the outer jacket.Ask your library if they can get the book for you called "Homemade Hot Water", Cannot remember author's names.Good luck and let us know what works!

-- maureenb (, April 14, 2001.

MaureenB pretty much summed it up. The old Mother Earth News had an article once on it. They just removed burner and gas valve, etc from water heater and lined area under tank with refractory cement. You dont need a large firebox. Also used to be some cheap wood water heaters from Mexico with option oil drip burner if you didnt want wood. Also ran across a US producer website with more expensive, more sophisticated commercial wood water heaters. Cant remember the name but you could use a search engine.

Make very sure you have a working pressure relief valve if you build one and intend to use it on a pressurized system.

At one time when I lived without running water and had access to an open dump, I built an outdoor shower out of salvaged parts. Cut bottom off electric waterheater tank (leaks usually occur at bottom) and inverted it, welded on legs. Ran steel pipe from bottom to pump I salvaged off old automatic washing machine and powered with small lawn mower engine. From pump ran hose with kitchen sink sprayer on one end to a wooden shower stall. Build a fire under the tank and about a half hour later, could take a nice hot shower. With open top, no pressure worries and can easily add cold water to adjust water temp if it gets too hot. Didnt cost me a dime, just time and thought.

-- Hermit John (, April 14, 2001.

Deborah, there is a procuct, made in Mexico, which would likely be exaclty what you're looking for. It's a wood fired water heater; it has a little firebox under the tank. It only costs about $175, depending on where you buy it.

I know that Real Goods ( sells it, but they are generally more expensive than most. I don't remember where else I've seen it. You could probably do a search on and go right to the manufacturer, or find retailers.

I had a real killer wood powered water heater that I built at my last house. I built the wood heater out of 1/4" plate steel, and made one side double layered, with one inch in between the two plates. This was the area where the water got heated. At the top of this "water jacket", I welded on a one inch pipe fitting, and another one inch pipe fitting was welded on at the bottom of the water jacket.

These two pipe fittings were connected to the two fittings on my (formerly) electric water heater, from which I had removed the heating elements (they are threaded into one inch pipe fittings on the tank). I made sure there were no high spots in the connecting pipes which could trap air.

This system gave us more than enough hot water to supply a home with five people. It also heated the house, since three sides and the top of the wood heater were not water jacketed.

If I were to do it over, I'd make all the sides of the heater water jacketed, and only use it to heat water. The water jacket keeps the temperature of the firebox too cool to allow real efficient combustion.

My new house's wood heater (a Quadrafire) heats my house, with about a fourth as much wood as the old place, and I wouldn't want to screw up its efficiency.

I suspect you could build your own water heater using a gas water heater tank, as you mentioned. I suspect also that you'd have to keep the firebox, and the fire, pretty darn small to get it to draw through the small chimney in the gas water heater tank, though.

Let us know what you end up doing. Wood heated hot water is really a good way to avoid a lot of energy bills.


-- jumpoff joe (, April 14, 2001.

one of the best things we did when re-doing our home is to install an on-demand hot water heater, heated by propane. there is no tank and the only thing that keeps going is a pilot light that uses very little gas. they are used in Europe a lot. for our gas drier, hot water and gas stove we pay about $20 - $25 a month. the water heater was expensive to install ($500) but we have more than paid for it and never never never run out of hot water.

-- Mary R. (, April 18, 2001.

Thank you for all your answers. I did check into the on demand water heaters but they are too expensive for me. I live on $600 per month..for two people. So I am looking at ways to do these myself. Thank you again.

-- Deborah (, April 18, 2001.

Many years ago i did just what your asking Deborah. I used an old 30 gal gas water heater. I used a 5 gallon plastic bucket as a form with a smaller plastic bucket inside which left about a 1 1/2 or 2 inch wall and floor in the firebox. Into this form I poured refractory cement. After it set up I just peeled out the plastic buckets and then cut an access door for feeding the fire. After removing the bottom of the water heater and the gas burner apparatus I set it on top of the new firebox. If I recall right I then attached a sheet metal door with some type of closeable type of air shutter to control the fire. I doubt that it would have passed underwriters testing but it worked great and those free showers sure felt good.

-- jz (, April 18, 2001.

Realgoods used to have a 3ft.woodstove pipe section that had a copper tubbing that was coiled in the inside of the stove pipe.On the outside of the pipe was 2 threaded connections ,one was the cold water inlet the other hot water outlet. The idea was the water would run through the coil in the stove pipe and get heated before it left.It seemed like an easy thing to make.

-- SM Steve (, April 19, 2001.

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