Domestic Hot Water from a Woodstove

Discussion in 'Survival Articles' started by ColtCarbine, Mar 2, 2012.

  1. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

    ARTICLES - Wood - Obtaining Domestic Hot Water (DHW) from a Wood Stove

    Obtaining Domestic Hot Water from a Wood or Coal Stove

    Many folks have expressed a desire to obtain hot water from their stoves. First, I should mention that this article refers to Domestic Hot Water, meaning the water that is used to wash dishes, take showers, etc. A woodstove cannot produce the volumes of water needed to heat your home through a baseboard or radiator system. If you are looking to heat your entire home AND produce your Domestic Hot Water, take a look at some of the wood burning central heating systems. These produce your hot water AND heat your home!

    There are two different types of heat exchangers which can be fitted to stoves and used to heat your domestic water.

    1. External Heat exchangers - if the stove has a large flat surface on the rear, then a serpentine can be fabricated that goes against the rear. If it is enclosed with a layer of sheet metal behind this coil, it will provide better heat. I’ve had them custom made..but the same shops that make DHW coils (tankless heater) for hot water boilers. These coils were made from a finned copper (usually 3/4”), so much the better for heat exchange. You could make your own by using 180 degree copper bends, but use high-temp (silver) solder so the coils don’t come apart if they ever hit a very high temperature.This would only happen if they ran out of water and the stove was VERY hot. Input would be into the bottom of the coil, and output from the top. A pressure relief valve should be installed next to the coil…WITH NO VALVES BETWEEN THIS PRESSURE RELIEF VALVE AND THE COIL.

    2. Internal Heat Exchangers - A few companies make such an item, although it may not be easy to find. The best ones are small tanks or coils made of stainless steel. The kits come with instructions and a pressure relief valve. In order to install an internal heat exchanger, a hole must be drilled into the stove body. This may be a job for a professional, as you don’t want to compromise the safety or integrity of your stove. Internal heat exchangers produce more hot water than external ones, however this increased heating ability also makes them more prone to overheat. Make certain that your installation meets all local plumbing codes and that your pressure relief valve is piped down through the floor or in a direction where steam exiting from it will not be near a person.

    dhw1. rough example layout DHW

    In many installations a pump and control will be needed. The only exception is when the unit is close to a tank and can be set up for a thermosyphon (the rising and falling of heated and cooled water) loop. I have used 1/100 HP brass circulators (available from Graingers) along with an aquastat to make the pump turn off and on when the water at the top of the coil heats and cools. I usually set this control to go “on” at 140 degrees and “off” at approx. 120. This then circulates heated water back to the hot water storage tank.

    Here is another important article on the subject by our friends at

    Here is one company that makes internal stainless steel DHW for stoves:
    Woodstove Water-Heater Coil by Thermo-Bilt, stainless steel, for wood stove, corn stove, coal stove.
    Last edited by a moderator: Feb 6, 2015
  2. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

    Baseboard Heat
    Heating the Home with Water

    1. Boiler drain with new tee
    2. Ball valve (Must be open when stove is fired)
    3. Circulation pump
    4. Tee and boiler drain
    5. Tee and 30 lb. pressure relief valve (ASME approved) with piping to area of safe discharge
    6. Radiator elbow and automatic air vent
    7. Tee and 3/4" bypass to zone that will thermal convect
    8. Ball valve (may be adjusted according to needs)
    9. Tee and boiler drain
    10. New tee added between existing pressure relief valve and boiler
    11. Existing flow conrol valve - may be manually opened
    12. Existing hot water supply line
    13. Existing return, main line and circulation pump
    Woodstove Water-Heater Coil by Thermo-Bilt, stainless steel, for wood stove, corn stove, coal stove.
    Last edited by a moderator: Feb 6, 2015
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  3. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

    Domestic Hot Water
    DHW, or Hot Water for the Home
    1. Cold water supply line
    2. Hot water supply line
    3. Existing temperature/pressure relief valve
    4. 3/4" ball valves (ASME approved) must be opened when stove is fired
    5. 3/4 vent elbow and automatic "float type" air vent (ASME approved" installed in high point of line
    6. 3/4 temperature pressure relief valve (ASME approved, and rated for 210º F/150 lbs.)
    7. Circulation pump
    8. Piping from temperature/pressure relief valves to areas of safe discharge
    9. 3/4" hot water tempering valve (ASME approved)
    10. 3/4" copper tee
    Woodstove Water-Heater Coil by Thermo-Bilt, stainless steel, for wood stove, corn stove, coal stove.
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  4. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

    Install a coil for domestic hot water, or as many as three coils, for hydronic (water-borne) baseboard heat. Then use your stove, or your furnace, as an efficient hot water heating unit.

    To install inside the firebox, a hole saw is used to drill two 1-1/8" holes for the ends of the coil (inlet and outlet). The coil can be plumbed directly to your existing hot water tank. No special holding tanks are required.

    If your existing hot water tank is located higher than your stove, the hot water can circulate by natural convection. For this setup, the only additional fittings may be a one-way check valve in the line, and one temperature/pressure relief valve at the hot water tank.

    If instead your hot water tank is located distant from, or below the level of, your stove, an additional relief valve should be used near where the hot water line comes from the coil, and a circulating pump should be installed along the cold water line leading to the coil.

    In both cases, cold water is taken from the drain valve near the bottom of the tank, and the hot water returns through a tee at the top of the tank.

    If you have plumbing questions, we recommend that your coil be installed by an experienced plumber. All pipe and fittings should be a minimum of 3/4" diameter. The examples below for domestic and hydronic installations may be used as a guide for plumbers and/or stove owners to follow.

    Frequently Asked Questions

    QUESTION: Do I have to re-do any of my old plumbing?
    ANSWER: No, you can leave your old plumbing in place.

    QUESTION: But the hot water will be stored in the (electrically-heated/gas-heated) tank I currently use?
    ANSWER: Yes, and you leave the electricity turned off (or the gas turned off).

    QUESTION: But my water tank has only two pipes, the cold going in, and the hot coming out. How do I connect my stove to this without modifying those pipes?
    ANSWER: Your tank has a couple more places to connect pipes. This is for the path of stove-heated water (cold out ... hot in).

    QUESTION: Two more places to connect pipes? Where is that?
    1. The drain spigot at the bottom of the tank.
    2. The pressure relief valve at the top of the tank.

    QUESTION: Okay, but if I remove that valve, suppose I need a pressure relief valve!
    ANSWER: You move the pressure valve to a different location, that's all.

    QUESTION: Will the water remain in the stove long enough to reach the temperature I'm used to?
    ANSWER: The water continuously circulates through the stove, that's how it gets just as hot.

    QUESTION: What keeps the water from getting TOO hot?
    ANSWER: This should not be a problem, unless your stove is a very hot-burning one (like a coal stove).

    QUESTION: Okay, suppose my stove burns extremely hot?
    ANSWER: There are quite a few different ways to "cool down" your hot water. One of the simplest is to install an in-line, variable speed circulating pump. The faster that the water circulates, the "cooler" it will be.

    QUESTION: Is a pump required to circulate the water?
    ANSWER: No. If your water tank is very nearby to, or at a higher level than, your stove, you can set up a passive circulation system (a thermosiphon). Cold water flows downhill from the bottom of the tank, and as it is heated in the stove, it rises (flows uphill) to be deposited at the top of your tank.

    Woodstove Water-Heater Coil by Thermo-Bilt, stainless steel, for wood stove, corn stove, coal stove.
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  5. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

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  6. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

    Fire and Water

    Domestic water heating from your woodburner

    by Art Sussman and Richard Frazier


    Steve's Note: Click the illustrations to see a larger version. You will want a tempering valve as wood fired hot water can burn you due to high temperatures. Contact me for sources.
    Anyone already persuaded to go with wood heat in his home ought to be a soft touch for this next idea. You’ve got the heat, now add a pipe or two and rid yourself of the second most gluttonous energy consumer in your home, your water heater.

    The average family in 1977 spent about $250 For water heating, which should tell you something about payback time. After a year or two your wood water-heating system will be paid for and more or less self-sufficient, the only cost being wood for your stove.

    If you burn wood all year you can take care of all your water needs, but if you’re like most of us you won’t want to stoke a fire during the warm months, and a back-up system of gas or electricity will probably be necessary. But the best method for obtaining year-round hot water is to use a simple, low-technology solar water heater during the summer. In spring and fall both the solar collector and the wood stove would heat your water. In the winter, stove heat is all you’ll need.

    There is a reason for using a dual system, and not just the solar water heater all year. It turns out that using solar power alone to heat water in the cold, often cloudy wintertime requires a more complicated, costly system. Cheaper simpler low technology devices can provide year round hot water if your winters are exceptionally mild; in colder climates, these sun-powered heat exchangers nicely complement the wood systems or even fossil fuels. In reality, there is very little added complexity involved in using more than one energy source to heat your water.

    Two complementary systems often provide more benefits than a single uniform system. The optimum solution to the energy shortage involves people in different locations using the power sources most available and appropriate to their situations. Thus, people in the southwest can use passive solar heating while New Englanders can rely on wood burning for warmth. Ignoring people’s capacity for the common sense to use locally appropriate energy sources, energy experts argue that solar heating isn’t practical since it won’t heat homes everywhere, that therefore we need nuclear power stations. These arguments fly in the face of reason as well as nature’s law that the ability to diversify and adapt to local conditions is the key to biological well-being and longevity. In contrast, the concentration of efforts and abilities in only one direction yields only temporary advantages which are doomed to extinction when inevitable changes occur (such as depletion of energy sources or accumulation of toxic wastes).

    Controlling convection
    The basic principle underlying the operation of both conventional and alternate energy water heaters is that hot water rises. An ordinary water heater is nothing more than an insulated storage tank sitting over a gas or electric burner (see figure 1). Since hot water rises as it is heated, cold water is piped in at the bottom of the tank while hot water is drawn off the top.
    Now let’s look at a typical alternate energy water heater. Figure 2 shows an alternate energy heat exchanger connected to a storage tank. It doesn’t matter if the heat exchanger is a solar collector or a grid of pipes in a fireplace or a stovepipe coil on top of a wood stove; the fundamental principles are the same for all three. Cold water from your water supply enters the bottom of the tank at "A." As in conventional heaters, hot water leaves the top of the tank at "B." The water heating circuit takes the cold water from the bottom of the tank, passes it through the heat exchanger and discharges the newly heated water at the top of the tank. Many systems use thermal convection – the process of hot water rising and cold falling in a container – to move the water in this circuit through the heat exchanger. In thermal convection or thermosiphon systems, you can have a complete hot water system without any electricity since the power from the sun or the burning wood provides the energy for both heating the water and circulating it between the heat exchanger and storage tank.
    In Figure 2, cold water leaves the tank at "C," travels upward through the coil as it is heated and continues into the storage tank at "D." Hot water rising through the coil draws cold water from the bottom of the tank (which is in turn heated in the coil), it rises, drawing more cold water behind it. This circulating motion – taking cold water from the bottom of the tank and discharging hot water at the top of the tank – fills the storage tank with hot water.

    By properly insulating your storage tank, the water remains hot long after the fire has died out. In our experience, the water will stay hot in a well-insulated tank for 48 hours or longer.

    Finding a tank
    There are a variety of sources for an appropriate storage tank. But the most obvious candidate is your present water heater. In fact, you can use your operating water heater retaining its power supply as a backup system or you can totally unplug or de-gas the tank and use your water heater simply for storage.

    If you don’t have a water heater, it’s easy to obtain a storage tank. Most discarded water heaters are abandoned because of breakdowns in the thermostat or heating element. These heaters are
    perfect for your purposes. You’ll want a tank that has no leaks and isn’t too badly rusted. You can find one of these storage tanks at the local dump, the power company or in abandoned houses. Local plumbers handle quite a few broken water heaters and can probably get you a good one for $5 or a basket of snow peas.

    For the thermosiphon to work circulating the water from the heating device to the storage tank, the tank must be located above the heat exchanger. Remember that we are depending on the tendency of hot water to rise to provide the power for circulating the water through the water heating circuit. In Figure 3, note that opening "X" is above or level with opening "2"; opening "Y" is above opening "W". Opening "Y" must be above "W" because it is the rising column of hot water in the pipe that forces the circulation of water through the system and replaces cold water in the tank with hot water. The higher "Y" is above "W," the better.
    In deciding where to place the storage tank horizontally relative to the heat exchanger, remember that the higher the rank is above the heat exchanger, the further you can move the tank horizontally away from the heat exchanger. A convenient (but not entirely accurate) formula to use is that you can move the tank two feet horizontally for every foot that "Y" is above "W." Figure 4 shows various ways that you can locate your storage tank relative to a fireplace or woodstove heating coil. The tank can be placed in a loft, in an adjoining room or even outside the house; Each gallon of water weighs about eight pounds. Thus, the stand for a 30 gallon tank should be able to support at least the weight of two people.​
    Some people already have water heaters in their basement and do not find it either psychologically or physically possible to change their plumbing so the water heater or storage tank is above their alternate energy heat exchanger. The easiest way to surmount this difficulty is to use a pump to circulate the water from the water heater through the heat exchanger.

    The second way to keep an operating water heater below the heat exchanger and still enjoy many of the financial and energy savings of alternate energy is to use the heat exchanger as a preheater for the current water heater. This method, shown in Figure 5, involves setting up a thermosiphon storage tank and feeding the hot water from it into the cold water inlet of your water heater. A single tank system is probably better in general, but the preheating method might be the better system if you want to keep your water heater operating in the basement and don’t want to use a pump to circulate the water between the heat exchanger and the water heater.
    Piping hot
    Let’s next examine the water heating circuit connecting the heat exchanger to the storage tank. Use the former drain opening for piping cold water from the bottom of the tank into the heat exchanger. This is quite simple. A more complicated method is piping the hot water from the heat exchanger into the top of the tank. In the good old days, when many people used pipes in the firebox of their wood cookstoves for heating water, they had tanks with upper side openings (see Figure 6). These tanks are still readily available, but if you can’t find one and are a competent welder (or have access to the services of one), you can burn a hole in your storage tank and weld in a 3/4" iron pipe coupling along the side about 3" down from the top and in a straight line above the drain opening. If your tank is galvanized, have good ventilation when welding and avoid breathing the poisonous gas formed by heating galvanized metal to a high temperature.

    There is another way to pipe the hot water from the heat exchanger into the top of the tank. Notice that your tank has several threaded openings in the top, through which you may be tempted to pipe the hot water from the heat exchanger directly into the top of the tank. As shown in Figure 7, this method won’t work, because any air in the system will collect and get trapped in the area of pipe indicated by cross-hatching. This trapped air will impair the heat driven circulation of water through the heat exchanger.
    Antisiphon devices are available to prevent cold water from the bottom of the tank from bypassing the tank through the heating coil and diluting the hot water at the pipe above the tank. To keep air from building up in the pipes during long intervals between draws at the tap, it’s best to install an automatic air vent at the top of the thermosiphon loop (Figure 8).


    The drawings show only one heat exchanger connected to the storage tank, though a combination of wood and solar water heating provides a more complete alternate energy water heating system for most people. All you need to do is connect the second heat exchanger via two tee’s into the pipes connecting the first heat exchanger to the storage tank (Figure 9). Be sure to install a pressure relief valve, as shown, for safety when the collector heats with other valves closed. Figure 10 shows. a cutaway drawing of a house with a rooftop solar collector and a stovepipe coil feeding into a storage tank in the loft.
    firean10. firean11.
    Wrap it up
    If you’re using both wood and sun, you can expect to meet all your hot water needs without a gas or electric backup. Still, you’ll probably want to have the gas or electric available if you use very large amounts of hot water or if you can take advantage of only the sun or only wood water heating, so don’t disconnect them altogether.

    No matter how you heat your water, be sure to insulate the tank well. The entire tank can be encased in 4" or 6" thick fiberglass insulation. This insulation comes in 16" wide rolls and can be bought at your local building supply or lumber yard. To hold the fiberglass in place, wrap the whole insulated tank in non-combustible material and stitch up the seams. If your tank is going to be exposed to the weather, an additional covering of plastic (keep it away from the gas flue) is needed. If you use gas for heating your water, you must leave adequate space for air to reach the gas burner at the bottom and for the hot gases to escape through the vented flue opening at the top.
    Instead of using fiberglass, you can insulate your tank by building a box around it and filling this box with natural materials that will create air traps. Some suggested materials are wood bark, sawdust, chicken feathers, wool, rags, egg cartons, wood shavings, etc. But if you’re using gas, avoid flammable materials.

    Insulation will also help maintain the temperature of the water. If you want hotter water, insulate the pipes between the storage tank arid the heating element (you should do this for most solar collectors though it is often not necessary for wood fire heat exchangers). If the distance from your storage tank to the hot water faucet is long, you may wish to insulate those pipes.
    These alternate energy-water heaters, like conventional water heaters, use a temperature and pressure relief valve as a principal safety device. This valve opens when the temperature or pressure inside the tank exceeds a preset level, and releases the overheated water. The released water should be piped to a safe place. It’s wise to limit the size of the heat exchanger to minimize overheating the water while producing an adequate supply of hot water. You can program the amount of hot water produced in your system by varying the size of the heat exchanger, the size of the storage tank and the amount of insulation.

    What’s best?
    Let’s look at wood fire heat exchangers in more detail. People burn wood in many different ways. For example, you can use fireplaces, cast iron box stoves, cook-stoves, airtight stoves with internal baffles, fireplace stoves, barrel conversion stoves, potbelly stoves, thermostat controlled air-tight stoves with sheet metal walls, and thick steel airtight stoves with internal firebricks. These woodburners have a variety of relative advantages and disadvantages that determine which would be most ideal for your situation. A variety of heat exchangers is available, and the one to choose depends primarily on the kind of wood heater you have.

    A pretty but inefficient place to burn wood is a fireplace. The inefficiency results from the fact that most of the heat escapes up the chimney. In addition, warm air from the room is sucked by the fire through the chimney and is replaced by colder air from the outside. Still, the radiant heat from the fire warms the immediately adjacent area sufficiently for some situations.

    The heat exchanger that works best with fireplaces is a grid of black iron pipe, arranged to get maximum exposure of the pipes to the flame. Iron pipes should be used here; they’re sturdier than copper pipes and therefore more resistant to the rough handling that a fireplace heat exchanger will receive.

    The woodstove attains a higher wood burning efficiency than the fireplace because of its ability to control the amount of air that enters the firebox. Many different airtight stoves are available that enable one to totally shut off the air supply of the fire. In these stoves, wood can burn over a much longer period of time and overnight fires can be the rule rather than the exception. These stoves generally use the wood more efficiently because of this enhanced control of the air supply and due to internal baffles, secondary combustion chambers or other design features that aim to burn all the combustible materials in the smoke before it can exit from the stovepipe.

    Watch your stovepipe
    Airtight stoves have cooler stovepipe smoke because they often burn wood more slowly, as when you load your stove and close the air inlet. When the smoke going up the chimney is cool, creosote condenses on the interior of the pipe. At higher temperatures, the creosote-causing compounds are burned or remain as a gas and escape up the chimney. But the reality is that many airtight stoves, when operated in a long-burn mode with limited combustion air, tend to accumulate creosote.

    The cure for creosote accumulation with all stoves is to regularly inspect the stovepipe. You will soon learn how often you have to check its condition. For masonry chimneys, the art of the chimney sweep is reviving. The chimney or stove-pipe can be cleaned manually with brushes or with a piece of cable lowered through the stovepipe. Or, you can use commercially available powdered salts which are sprinkled on hot roaring fires in weekly treatments. These salts help burn up the accumulated creosote (by lowering its ignition temperature) to prevent it from reaching a critical mass where it could burn out of control in your stovepipe.

    We have explored the world of the stovepipe in detail because one of the simplest woodstove heat exchangers involves placing a coil of copper pipe within the first section of stovepipe above the stove. Since this heat exchanger extracts heat from the flue gases for water heating purposes, it cools the stovepipe smoke. If you use too large a heat exchanger or if your stovepipe smoke already tends to be cool, this cooling of the smoke will cause unacceptable accumulation of creosote. That is why stovepipe water heating coils are not used with airtight stoves.

    Figure 11 shows different woodburning stoves and the heat exchangers recommended for various situations. Basically, the stovepipe coil is recommended for non-airtight stoves like the cast iron box stove and the potbelly stove. It is not recommended for cookstoves since these have cool stovepipe smoke due to their small fireboxes and the dissipation of most of the flue heat to the oven and cooking surfaces.
    With airtight stoves and cookstoves, place the heat exchanger directly in the firebox since the stovepipe smoke is often too cool. You can use either the flat firebox grate of iron pipe (as in a fireplace) or a coil of copper pipe shaped to fit your stave. In either case, the heat exchanger should be exposed to a maximum amount of direct flame but not interfere with putting wood inside the stove. This usually involves placing the heat exchanger in the upper back of the stove or along a side wall.

    The previous was an excerpt from the book, Handmade Hot Water Systems
    Home Energy Digest & Wood Burning Quarterly, Summer 1980, Pages 161-176 ​
    Last edited by a moderator: Feb 6, 2015
  7. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

    Another manufactured hot water coil for wood stoves:

    Therma-coil Woodstove Water Heating_plumbing


    Thermosiphon (passive) Method

    The easiest, most economical and desirable method of Thermo-coil water heating is the thermosiphon, using no pumps, controls or electricity. Heated water from the Therma-coil is less dense, lighter, and naturally rises to the top of the water-heater or storage tank. The cooler water in the bottom of the water-heater/storage tank is heavier and "falls" down the plumbing line to the Therma-coil, completing the cycle. The flow is slow and is reduced by long runs. This is only possible if the water heater or storage tank is higher than the woodstove and close to it. An ideal thermosiphon arrangement would be to place the water-heater on the next floor above the woodstove, in an attic, closet, or elevated in the garage opposite the woodstove wall (a stand can be built under the water-heater).

    Sloping the piping at least 1 foot rise for every 2 feet horizontal run would be a good rule of thumb using 3/4" (well insulated) copper pipe. Soft copper reduces sharp turns and is easier to install in most situations. Local plumbing codes and methods should always be adhered to.

    thermosiphon. IMPORTANT!

    Always vent the pressure/temperature relief valve to a safe place in case overheating occurs.

    Pumped (active) Method

    When the water heater isn't located close to and higher than the stove, a small circulator pump and controller is used. The differential controller compares a probe sensor inside the bottom of the water heater / storage tank, and a probe sensor inside the therma-coil exit line. Whenever the stove water is hotter than the storage tank, the controller turns on the circulating pump. The pump circulates the cooler water from the bottom of the water heater, through the Therma-coil where it is heated, and back to the top of the water heater (costing only pennies a day in electricity.)

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  8. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

    Last edited by a moderator: Feb 6, 2015
  9. chelloveck

    chelloveck Diabolus Causidicus

    Thank you CC

    Thank you CC for the well explained, well documented and well illustrated series of posts highlighting various different active and passive fuel stove domestic hot water systems. They seem relatively simple systems to create, by the self instructed amateur off grid plumber. Thank you also for the links to other sites on the subject. I haven't checked them out yet, but it is a useful resource to be able to tap, so to speak.

    Although mentioned in various places in the articles that you have posted is the necessity of installing pressure release safety valves,I would like to stress the importance of not neglecting this important safety feature, as well as the importance of periodic system maintenance activity...a pressure release valve that hasn't been installed, or installed incorrectly, or that isn't fully functional is as like to ruin your day, and possibly your house (1) if it fails when a critical pressure state has been reached.

    The other thing that may need to be considered, is that in many jurisdictions, hot water system installations may need to be inspected and authorised by a qualified / registered plumber or compliance inspector. This particularly is likely to be the case for town and village dwellings. This requirement may be also necessary for rural dwellings, though, possibly "official interest" may not be so actively concerned, the more remote the dwelling is in the boonies. A HOA is probably going to come down on ya like a hornet's nest if you jury rig something that doesn't gell with their sense of aesthetics. : O Which is probably why you would be off grid in the boonies in the first place. ; )

    Note 1. This link demonstrates the effect of a hot water heater that's pressure safety valve has failed.

    Water Heater Blast!
    Last edited: Nov 13, 2017
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  10. TnAndy

    TnAndy Senior Member Founding Member

    You'd actually do well to install 2 valves, and keep a couple spares around. They DO fail, and fail to work, especially if the water in the heat exchanger in the fire box turns to steam real quick.

    I had a self made "boiler" for years and years in my fireplace, using black iron pipe for a firegrate and circulating water thru it to a 500 gallon storage tank in the basement. I had one pop-off valve located just outside the firebox in a chute that goes to the basement ( I have a homemade "dumb waiter" affair that I load wood in the basement, and winch the wood car to the 1st floor level where the fireplace is located ).

    I could often build a fire in the fire place that would turn the water to steam REAL quick in the grate...faster than the "aquastat" in the return line would react and turn the supply pump on at the basement tank....then the popoff valve would open, and sound like an Atlas Rocket going off in the wood chute !

    Once, it failed to open, and the resulting pressure blew the return line ( type L copper ) apart in the basement. Had anyone been down there, a pretty good scaling would have resulted.

    I solved the "cold fireplace" deal by simply installing an override switch up next to the fireplace, and turned the pump on manually whenever I started a fire so water began circulating immediately. Put a little LED light on it to remind me the pump was in "over ride ", and would turn it off later as the inline thermostat took over the pump operation.

    All that has since been replaced with a far more efficient wood stove insert that burns about 1/2 the wood of before, but sometimes I miss that big open fireplace ! ( just not at wood cutting time....ahahahahaha)
  11. rsbhunter

    rsbhunter Monkey+


    What an awesome reminder of what we don't ever think about!...9.3 seconds of air time on the tank!!!!!!!! Hope everyone see's this and pays attention...only takes a minute to check the valve.......and avoid alot greater price paid, in cash or lives...rsbhunter
  12. BTPost

    BTPost Stumpy Old Fart,Deadman Walking, Snow Monkey Moderator

    Ok, Colt Carbine has given you the facts of the domestic Hot Water System, in this thread. Here are the pictures of "My System" that has been in place for 30 years. This works 24/7/365 and makes ALL our domestic Hot Water.

    Same design as in Post #7 Thermosiphon (passive) Method

    Picture 1 Shows the firebox with coil, (4 turns 1/2" Copper Pipe) in our Diesel Fired, Pot Burning CookStove.
    Picture 2 Shows the backside of the stove with the coil connections to the Thermal-siphan Loop to the Hot water Tank. Notice that the coil is connected to a set of Valves, by a Union on each end. This makes it easy to swap out the coil, without draining the whole Hot Water Tank. Just close both valves, and the crack the unions and drain the coil, then replace the coil, and reconnect the Unions and open the vales again, to Service.
    Picture 3 Shows the Top of the 200 USG Domestic Hot Water Tank. (with Notes)
    Picture 4 shows The bottom of the same Tank. (with Notes)

    This tank lives on an inside wall, in the cabin. It also functions as a Heat Radiator for the Main Room in the cabin.
    The tank is an Inspected Pressure Vessel, and does carry a certificate, as does the Relief Valve.

    ..... YMMV......

    Firebox coil. Coil connection. Tank top. DHTank.
    Last edited by a moderator: Feb 6, 2015
  13. rsbhunter

    rsbhunter Monkey+


    Thanks for showing us that all the theory can be done in a (fairly) simple way...Alot of the alternative water and heat systems are almost more intimidating than solar electricity!!!..Something about having a potential bomb in the house that I constructed causes me to ponder on my intelligence...but to see it in real , been there , done that pics, make it seem doable...Thanks for taking the time to post the pics with captions...cause without the captions, it would have been confusing to alot of us considering doing this...rsbhunter
    chelloveck and Tully Mars like this.
  14. ghrit

    ghrit Bad company Administrator Founding Member

    Be aware of two things when building a hot water system. If you are subject to a code inspector for an occupancy permit, he's going to look for ASME "U" code stamps on tanks and relief valves, no stamp, no permit to live in it. Also, your insurance guy will do something similar. (Without the stamps, your premiums are apt to be high.) The code stamps show that the components are certified to hold (or relieve) the pressure safely. Household hot water tanks are so certified, so no problem if you use one, and the same applies if you buy are relief valve at the hardware store.

    You should also place the relief valve discharge someplace that won't freeze. If it leaks a tiny bit, an ice plug can form and disable the function.
  15. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

    I highly suggest to anybody reading this thread and/or that does not have any experience installing any type of a hot water heating source, either have it installed by a licensed plumber or obtain advice on the installation and placement of appurtenances from a licensed plumber/mechanical engineer.

    The systems pictured above, only show the basic design of the piping configuration and placement of appurtenances. Not all installations are going to be the same due to structural conditions, location of existing hot water heater, location of wood stove and type of installation method/design that you are going to use.

    None of the above design methods show everything that is needed for a proper (safe) installation to meet plumbing code, they are basic in design.

    Even if you are not planning to obtain a permit and/or have it inspected, do yourself a favor and install your system in the same manner for your own/families safety. An improper installation can have a catastrophic failure, resulting in injury, loss of life and/or property damage. No kidding, do not take this lightly.

    BTPost thank you for posting pictures of your system, as I was hoping you would show off your system.

    Hopefully, TNAndy will do the same with his gas fired stainless hot water heater that was converted. I tried to find an example of this to no avail.
    Tully Mars, chelloveck and BTPost like this.
  16. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

    bump to the top
  17. Nadja

    Nadja RIP 3-11-2013 Forum Leader

    Just putting my two cents in here. There are solar "water heaters" made also that do a pretty good job of heating water for nothing once you have them installed. You could make your own out of black pvc pipe or copper pipe painted black if your rich enough. Simple operation and although I have never had one, a friend of mine did have one for years. Swore by it, even in the winter. Worth looking into me thinks
    chelloveck likes this.
  18. TwoCrows

    TwoCrows Monkey++

    It is well worth considering a solar water heater at least for summer use, who wants to fire up the wood burner when it is 100 degrees already ?

    About thirty years ago I had some friends who had a Monarch cook stove with a factory built water jacket and a huge hot water tank, it was their only source of heat and hot water and was always enough for both.
    chelloveck likes this.
  19. BTPost

    BTPost Stumpy Old Fart,Deadman Walking, Snow Monkey Moderator

    Bump to the Top
  20. RightHand

    RightHand Been There, Done That RIP 4/15/21 Moderator Moderator Emeritus Founding Member

    This is exactly the type of system my grandfather built in his own retirement home in 1954. When I moved in some 25 years later, the system was still functioning perfectly. He had converted an old boiler into the firebox and run the pipes through that. The house was always warm and I had all they hot water I could use and another advantage, chopping wood kept me slim and trim.
    chelloveck, Ganado and Tully Mars like this.
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