Domestic Hot Water and Wood Cookstoves: What To Know


Domestic Hot Water with Elmira Stove - Obadiah's Cookstove Community

A domestic hot water setup with an Elmira Cookstove.

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Many folks who want to live the self-sufficient lifestyle know how to handle their food: Hunting, gardening, and building a fire. Mastering the methods behind each of those tasks means you’ll never have to worry about starving, no matter the situation. But what about water? Specifically, hot water?

We all know water is more important than food for survival, but we don’t often think of the huge role that hot water plays in our day-to-day life. We should, though, because heated water is essential to minimizing bacteria in cooking, cleaning, and bathing. Of course, anyone can throw a pot on top of a stove or over a fire, but if you’re living in an off-the-grid household, your hot water needs will be much greater than any stove-top pot can offer. So what’s the solution?

Domestic hot water via stove.

Many woodstoves and cookstoves offer an option (typically for an additional but reasonable cost) for domestic hot water installations. Here’s how it typically works:

Water Jacket to Storage Tank

Domestic Hot Water - passive - Obadiah's Cookstove Community

Domestic Hot Water – Passive System.

A water jacket (also known as a “water coil”) is a block of steel that attaches to the back or side of your stove, and contains an entry and exit connection for piping. When water enters the block, it hits a chamber inside and slows down, allowing the water to become heated. This heated water is then forced out to your water storage tank, which is sitting above your stove.

The water jacket is connected by piping to the water storage tank. As cold water flows from the bottom of the storage tank and into the jacket, it becomes heated. That heated water is then sent back out through a separate pipe to the top of the storage tank, thus creating a tank full of hot water that can then be connected to where ever you need. This method relies on simple physics: Hot water rises, and cold water falls. As a result, no pump is necessary. This creates a thermoloop and is known as “thermosiphoning”, a passive system. You do need a specific valve to make thermosiphoning work, so make sure you use a brass swing valve. Do not use a check valve, especially one that is spring loaded, as it will not create enough pressure for the system to function. See this forum post for more information.

Domestic Hot Water - Pioneer Maid System - Obadiah's Cookstove Community

A passive system installation using a Pioneer Maid Cookstove.

Domestic Hot Water Installation - Cookstove Community

A thermosiphon setup.

For an example of a thermosiphoning set up, we have this installation from our friend Tim. Here, the tank on the left can be shut out of the system with valves, which helps to create hot water faster. To slow the creation of hot water, that tank can be activatied to allow longer burns before both tanks become overwhelmed with water that is too hot.

Note: Since this photo was submitted, the top of the second tank has been connected with hot water, and a tempering valve has been installed. You can read more about Tim’s installation in our forum on this post.

Keep in mind that some cookstoves can be ordered with a water reservoir in the form of a tank that fits onto the back of the stove. If a reservoir is not pressurized it cannot be connected to a domestic hot water system. They are fill and drain systems only, which means you fill it with a bucket and drain it into a bucket. If you buy a wood cookstove with a water reservoir and it is connected to a water coil when there is a fire in the firebox, there must also be water in the water reservoir, or it will melt. If you are going to use a water reservoir on a cookstove, it is best to look for one that has a water reservoir that is passively heated and can sit there empty until needed without a problem. This will eliminate many of the problems associated with the use of a reservoir when you have the luxury of turning a tap for hot water, but also need a back up source in case the power goes out. Hauling water to your stove in buckets is not easy, and it will seldom be used when it is easier to turn a knob for hot water. Over time the water will become stagnate or it will begin to boil and create steam, which can create mold and mildew in your home.

Pump System

Domestic Hot Water - active - Obadiah's Cookstove Community

Domestic Hot Water – Active System.

A pump system, by contrast, is an active system. This method of generating domestic hot water relies on an electric pump to create the thermoloop and a heat activated sensor to activate the pump when the stove is hot.

An active system can potentially produce more hot water and, as long you have power, there is less chance of dangerous pressure levels from the water overheating (the result of an active system producing more water movemnt). However, an active system can become complicated quickly: In the event of a power failure, an active system’s electric pump will cease and potentially lead to dangerously high pressure in the water jacket and piping. With this danger in mind, you must also install a relief valve within two feet of the water jacket that is piped to a drain.

Obadiah’s firmly believes that a passive system is the best way to go in terms of simplicity, safety, and expense. There may be circumstances where a pump system is the best (or only) option, but the benefits of relying on simple physics instead of electronics when attempting to live the self-sufficient lifestyle cannot be overstated.

Domestic Hot Water - Gravity System - Obadiah's Cookstove Community

This diagram shows a typical passive installation (sometimes referred to as a “gravity” system) for domestic hot water.

Is Domestic Hot Water Right For You?

So now you know the basics. The real question is, should you use your stove for domestic hot water? Depending on your circumstance, heating this way can be hugely beneficial. With a passive system there is absolutely no reliance on electricity, which will ultimatley keep your heating costs down during the cold winter months.

Kitchen Queen Water Coils - Obadiah's Cookstove Community

Water coils for a Kitchen Queen cookstove.

The key to using this type system is understanding that you cannot install valves to turn off the flow of water, or you will have an explosion when the water boils. When there is fire in the firebox of your stove, some of the BTUs will be going into the hot water tank, so you must have two ways to read the temperatures in the tank. If you don’t have a way to read the water inside the tank, you will need to install a temperature gauge on the inlet side of the thermoloop and on the hot side of the domestic hot water outlet on the tank, which will give you an idea of the temperature of the water going in and coming out of the tank. For example, if the water going into the tank on the thermoloop side is running at 220 degrees and the hot water coming out is 190 degrees, it means you have 20 degrees to go before the pop off valve will release and all your hot water goes down the drain.

The real catch with using your stove for domestic hot water is that it is a constant monitoring process.

Domestic Hot Water - Basic System Design - Obadiah's Cookstove Community

Example of a hot water system layout using a Kitchen Queen.

You will want to make sure you don’t blow your valve and lose your hot water by bleeding off the BTUs inside the tank when you use hot water at the tap, laundry, or shower. If you have a family, you can rotate your turns at showers and do laundry and dishes throughout the day to periodically use accumulating hot water. Another trick to get the most out of this system is to also drain the hot water tank at night (take showers, etc.), so that it will refill by morning.

This system works if you’re on a ranch, homestead, or farm, and everyone is around during the day. If everyone is going different places all the time, it won’t work because no one can monitor the water temperature. If that’s the case, the system has to be automated with aquastats, pumps, and a diversion system to bleed off BTUs into the something like a hot tub. These systems can get complicated quickly and the price can get expensive, so make sure you can run it with a battery back-up in case of a power failure.

So, how does all of this look in real life? If you worry that a domestic hot water installation will be a mess, fret not! Below are a few photos of a properly installed system that’s been connected to radiant in-floor heating.

By using your stove to heat water for domestic use, you will be taking a huge step towards total self-sufficiency. For more information on domestic hot water via stove, please check out our videos on the subject. There are also several free resources available online to help you understand a bit more about this unique way to heat your water:

  • Kitchen Boiler Connections: A Selection of Practical Letters & Articles Relating to Water Backs & Range Boilers, Compiled from the Metal Worker
    • Hot Water Supply and Kitchen Boiler Connections – William Hutton
    •  
      Cookstove Community’s Woody Chain also offers a basic installation walkthrough on our forums, check it out here if you need some advice on what to do next!

      Obadiah’s Domestic Hot Water Kit

      Not sure what parts you need to begin the process of getting a domestic hot water setup? Fret not! Obadiah’s has put together a comprehensive kit with everything you need for your system. Here’s what’s included:

      First, select your boiler tank size:
      Part # Part Price
      GW 40 40 gallon Range Boiler Tank – Hot rock lined welded heavy gauge steel $475 (plus freight)
      GW 80 80 gallon Range Boiler Tank – Hot rock lined welded heavy gauge steel $745 (plus freight)
      Next, pick up Obadiah’s Domestic Hot Water Kit
      Part # Part Name Price
      36DT Dip Tube for hot Rock Range Boiler $35
      2K501 1.1 gallon Expansion Tank $59 (plus freight)
      34-BD 3/4″ NPT Boiler Drain $11
      T571 Stick Style Thermometer Gauge $33
      SV-150 150 PSI Safety Pressure Relief Valve 3/4″ NPT (2 units) $44
      H25-18 Gauge Style Pressure and Temp Gauge $30
      FV180/U 1/8″ NPT Auto Vent Valve $15
      AM101-1 3/4″ NPT Mixing Valve $103

      Total Price: $317.
       
      Need to add a pump? Just include these parts (either on-grid or off-grid, depending on your living situation):

      Domestic Hot Water Pump Parts (on-grid, 120 Volt AC System)
      Part # Part Price
       006B Taco DHW Circ Pump 120 Volt Sweat $323
       L6006A  Aquasat Controller well type with stem $168
      Domestic Hot Water Pump Parts (off-grid, 12 Volt DC System)*
      Part # Part Price
      C-12V Laing 12 Volt Circ Pump 3 gal per minute 1.9 amps 1/2″NPT $295
      12VRELAY 12 Volt Relay for Circ. Pump $23

      *Note: A 12 volt probe type thermostat is needed to activate the pump, installed to spec. based on system requirements.

      Please note that these are general prices and are subject to change; all prices are provided for estimate purposes only.

9 thoughts on “Domestic Hot Water and Wood Cookstoves: What To Know

  1. Andrew

    Please change the drawing on “A domestic hot water setup with an Elmira Cookstove”, since it does not say a gravity or a pump system, the way the drawing is showing, you will get a steam build up and possible problems if a person does not realize, with a gravity system you can’t have your return line above your storage tank. I would think the best area in your tank would be in the middle and your “draw” at the top of the tank but that depends on the way the tank is refilled.

    If your hot water storage tank is above your facets and you vent your storage tank to the atmosphere, you will never have a chance of explosion. Because the vent will just allow the steam (if the water is super hot) to vent to the atmosphere.

    Like you said, a lot of people want to be off grid and that picture does not help be off grind, maybe homeless. I hope people are not relying on this post only for figuring out hot water heating. It is a good start but seemingly incomplete.

    Reply
  2. Woodstove Woody

    Greetings Andrew and thanks for the comments. You said, since it does not say a “gravity or a pump system”.
    When I reviewed it I found the terminology, ” Domestic Hot Water – Passive System” .
    and “Domestic Hot Water – Active System.”
    Sorry for the mis-communication. Passive is normally anything that is natural, physics such as Thermodynamics rather than gravity to circulate the BTUs in a medium such as hot water.
    An Active System would fall into the category as anything requiring a mechanical means to move it, a pump would fall into that category,
    As far as the rest of what you said, I am not following you, the lower diagram clearly shows a circulation pump the active system.
    There are other ways to do things rather than what is shown here. The system here is a viable way to do this. The way that you are referring to is common in Europe and very simple and yes I agree. I don’t agree that what we have demonstrated is wrong. Perhaps you would like to start your own article showing diagrams for this kind of system? We welcome others to share what they have done.
    In the meantime we’ll see about adding a diagram of an open system.
    Thanks,

    Reply
  3. Woodstove Woody

    Please make note that the diagram that shows the passive and active DHW system show a check valve in both instances. The check valve needs to be there for a system that is using a pump to circulate the water. I believe this to a Typo as the check valve should not be installed in a passive system as it will prevent the movement of the water flow. Themosiphoning is very gentle and it does not take much to stop the flow. What would happen is you would have surges as the water heats up to the boil point, and burps steam to release the pressure. You will not get a smooth temperature clime in your Range Boiler. Instead your system will be making strange noises and probably sounds like it wants to explode sometimes. Remove the check valve and your system will probably work smooth as silk.

    Reply
  4. SUSAN

    Hello, we have a flameview stove with a double coil. We have reliable gravity feed water. How do we hook up our flameview? We need a schematic.
    thanks

    Reply
    1. Chris Post author

      Hi Susan,

      One of the common complaints about the Flame View is the lack of directions included with it. We haven’t supported the Flame View in quite some time, but Woody drew up his own manual years ago and if he can find it that might help you out. You can send him an email over at woody@woodstoves.net. Good luck!

      Reply
  5. SUSAN

    Hi Woody,
    Wish I saw your forum before I bought the Flameview, I would have bought a more reliable stove! I wonder if we can sell this beauty?
    It’s getting cold here in the Kootenay, and we need to heat our house. However we found out that we can’t burn a hot fire without damaging our double-coil water-heater in the Flameview and we haven’t found a plumber with the know -how to connect the water coil system. ( my husband is working full time out in the field). Can we take the double-coil out and use the woodstove, like a normal woodstove? We’ve heated with wood for a very long time.
    thanks for your forums,
    Susan

    Reply
    1. Chris Post author

      That’s correct Susan, you don’t want to start any burns in the stove with the water coil hooked up if there is no water available. Thankfully. the Flame View does not require the double-coil to operate, so you should be able to remove it and use the stove as a standard woodstove/cookstove.

      Reply
    2. Woodstove Woody

      I am adding this information as a means to help other Flameview Cookstove Owners who are also wondering how to remove the Double Hot Water Coil from their cook stove, it simply unbolts.
      1. Remove the bolts (2) in the top firebox, that are in the bracket the tubes are welded to.
      2. Slide it out, and remove it.
      3. You must plug the holes using the same two bolts that held it in, by adding some fender washers to close the hole off.
      4. A little dab of furnace cement would help too. Add one washer inside the firebox and add a dab of furnace cement push it against the firebox wall to hold it in-place, repeat on the outside of the firebox.
      5. Tighten and your ready to fire your Flameview Cookstove.
      6. Grab a fire extinguisher and keep it nearby.
      7. Buy a Chimfex that you can toss into the firebox if the stove catches fire.
      8. Make sure you keep it cleaned and make sure that you dig out the creosote at the base of the chimney system that goes through the warming oven.
      9. The only way in there is through the top of the flue collar down. You must dig the creosote out of this area in order to properly clean this a Flameview Wood Cookstove. If this area ignites it will burn at over 2000 degrees! Printed clearances do not allow for this.
      10. Keep the area around the oven clean as well as this side is prone to build with creosote.
      There is another post on Hearth.com that talks about another Flame View Cookstove and how to clean it properly. https://www.hearth.com/talk/threads/does-anyone-have-the-margin-flameview.113187/page-2

      Reply
  6. Woody Chain

    Susan,
    I am still making trips to the Yaak almost every weekend as long as the pass remains open, to work on my place and get ready for Burrr season.
    Call me and maybe I can swing by and help. I will be back up there in the West Kootenay, Friday Nov 11th, looking at the local Vet’s boiler installation.
    Sorry about your Flameview, I still have the one I made the video about and have not been able to find a buyer either after 3 yrs. now. I guess the video opened some eyes. We had hoped it would be Margin Stoves eyes and we could offer a improved model, the way JA Roby changed the Cuisinier after I brought those issues to their attention. But they still wont talk to me until I remove the videos I made about the Flameview. The Margin Gem is one of the best antique re-pros on the market and we said so, we still recommend it when asked for new Antique Cookstoves. Very unfortunate, but I stand by what I demonstrated in the video.

    Reply

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