Use Your Wood Stove as a Water Heater

Your wood stove can heat more than your home. This hot water heating system uses extra heat to produce hot water that will stay warm up to 48 hours!

| November/December 1976


Figures 3 and 4, showing placement for your water storage tank.


Three years ago, we were sitting in our cabins wondering how we could satisfy our addictions for hot baths and showers, without paying ridiculous prices for disappearing reserves of fossil fuels. Putting our talents together (one of us is a mechanical wizard and the other a Ph.D. chemist), we devised a homestead alternate energy system — based on the use of otherwise-wasted stovepipe heat — that's allowed us to take those hot baths. We call our system the Blazing Showers Stovepipe Hot Water Heater.

Hot Water Basics

As you can see in Fig. 1 (see Image Gallery), an ordinary water heater is nothing more than a storage tank (located between a house's water source and its various hot water faucets) sitting over a gas or electric burner. Since water tends to rise as it's heated, cold water is piped in at the bottom of the tank, while hot water is drawn off from the top.

Fig. 2 compares such a conventional water heater with a Blazing Showers system. As you can see, our setup employs a coil of copper tubing — located inside a wood burning stove's stovepipe — to heat the water that's held in our storage tank. Hot smoke rising through the stovepipe warms the water in the copper coil, which causes it to rise (and thereby draw more cold water into the coil). Meanwhile, the stovepipe-heated water flows into the top of the storage tank, where it remains until someone decides to take a "blazing shower" and turns on a faucet.

Notice that there are no pumps in our system: Instead, plain ole thermal convection does all the work.

Hot Water... Overnight!

How long does it take to fill a tank with hot water this way? The answer depends on how cold the incoming cold water is, how many gallons your water heater holds, and how hot the flame is in your stove. We estimate that a blazing fire in an average-sized wood-burner can produce 20 gallons of hot water per hour. And—if you store that heated water in an insulated tank as we prescribe—it'll remain hot for up to 48 hours after the fire goes out. What this means in practical terms is that if you have a fire in your stove one evening, you'll still have all the hot water you want (for bathing, dishwashing, etc.) the following morning when you wake up. In fact, that water will actually remain warm for two full days ... even if you don't light the stove again at any time during that period.

First Things First: Storage Tank

The first thing you need before you can install a system of your own, of course, is a storage tank. If you already have a hot water heater, you can use it ... otherwise, look around for a "previously owned" unit.

10/31/2017 4:04:27 PM

We are off-grid but not highly mechanical, though we aren't doing a bad job at it. I love the idea of heating water with the wood stove but have one point where I don't understand the process clearly from your diagram. I see that the heated air can become trapped on rising and going into the water tank, but what do you actually do about it, what is the item you mention and where do you put it? My artist/writer brain needs a very simple diagram/instructions for that!

10/31/2017 4:04:25 PM

I love the idea of using the woodstove to heat water and being off-grid, it would be especially useful to us in the winter. We are doing pretty well in our situation though we are neither of us highly mechanical which makes even the simple diagrams like these an effort for our brains! However, I can understand the mechanics of how it works, though I don't understand what we would actually do to prevent the trapped air you mention as the hot water goes into the tank. What is the part you have invented, where and how is it attached? I'm an artist, writer and singer, and the only-slightly-mechanical part of my brain lost it at that point!

10/1/2014 10:31:02 AM

The Kitchen Queen Wood Cook Stove has a feature making it easily available to use for heating your water. If you go to this link you can look at it more in depth.

12/16/2013 2:41:51 PM

I know this is an old topic, but I'm looking for some feedback on something I'm wanting to try. Our home has a fuel oil boiler system with baseboard registers and hot water heat. Works great but who can afford to operate it at $4.00/gal for the fuel. We've been using wood heat with a Lopi wood stove in our living room, but our basement, bedrooms and bathroom get pretty cold comparatively. What I want to do is install a Blazing Showers Stovepipe Hot Water Heater and rather than hook up to water heater, hook it up to my boiler system so we can heat the house completely. Once tapped in, I think all I would need to do is have the existing circulating pump going continuously to keep a steady flow going. Everything needed is already incorporated into the lines, like the pressure relief valve, tempering valve, circulating pump, air bleeder valve. All there. I'd like to keep all intact so we can use the fuel oil boiler as backup. Maybe hook in our electric hot water heater as well. Does anyone see anything wrong with this picture, and is it possible to buy one of your heaters somewhere, or should I make my own?

valerie bronz
4/11/2012 3:04:56 PM

I saw this same type of heating about 20 yrs ago an thought itwas wonderful. My question is can this be easily adapted to flow threw floor piping to supliment your heat and keep those floors warm in winter?

duane weed
6/27/2010 7:25:05 PM

Where can I get the adapter assembly that screws onto the hot water outflow pipe at the top of the storage tank which contains the anti-siphoning device (at Y in figure 2)? Thanks

roland green
2/12/2010 2:27:07 AM

In Figure 2 the pipe work from the heating coil does not appear to return to the storage tank, but appears to feed directly to the fixtures. Surely the heated water should return to the storage tank otherwise the water in the heating coil, being static when no tap is being turned on, would soon overheat and boil. I would see the return from the heating coil entering the storage tank about the same level as 'W' allowing for convenction circulation of cooling water from above that level. Secondly, I assume that this system is a gravity fed system from a water storage tank in the attic and not pressurised because again, if the hot water is not used the storage tank could soon overheat and most likely burst as there is no way to control the heat. As a safety feature, rather than a safety valve the storage tank can be vented by a rising pipe, either directly to the open air, or venting into a header tank in the attic, which would be level with the general water stoage tank.

gary reysa
6/1/2009 8:03:45 PM

Hi, Good article -- thanks! One safety precaution I think should be emphasized is that these system should be protected with a pressure/temperature relief valve, and that no shutoff or bypass valves should be installed in the system that can isolate the stove from the PRT valve. Steam explosions that can result from water being heated in a stove coil can be extremely violent as this link shows: Gary

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