DIY Woodstove Powered Hot Water Heater System Introduction

A DIY hot water heating system that uses the heat from a woodstove in a SAFE manner. In this video, I lay out my initial plan for how this system has been designed, and in subsequent videos, I'll share the construction and performance of the DIY woodstove water heating system.
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[@sarahgrooms5606]

I have a Joolca hot tap, it might be spelled wrong. It comes with a system like hot water on demand from cold water and propane. It only kicks on when you take a shower or you can use it to wash dishes. It's made for outside showers but I had it inside. Works very good.

[@PraxisPrepper]

One of the things that has held me up SO long on fixing my not that great system I have is because there ARE (as you noted of your own solid system) so many great options from which to choose about how to address things and make them better. It's been a long while of me pondering what's the best way to go about fixing this from option overload. :)

[@DumpsterElite]

We had a 40 gal propane hot water heater that just bought the farm a few months ago. I was trying to stay ahead of my whackadoodle governor here in NY State, who is trying to outlaw gas and propane. So I went with an electric hot water tank. But there are only 3 of us here. So I "experimented" with a smaller 19 gal electric tank. Set it at 130 degrees, and we have 15-20 minute hot showers. Wasn't sure if I would need anything additional with it at first, but it is working great so far. I'm saying all this, as it might be an alternative solution for you in the winter, if your tank is a 40 gallon. Takes a lot less power to heat a 19 gallon.

[@PraxisPrepper]

That's all food for thought. As the tanks get bigger though, their volume to surface area ratio goes up, so they tend to be able to hold their temperatures better over time. An example being that if a mouse (with fur) and an elephant (with no fur) both die in the winter cold (let's say while Hannibal is marching his army of elephants and mice over the alps), even though the mouse has insulating fur, the dead elephant will stay warm at the core WAY longer than the dead mouse will due to that ratio of inside volume to exposed surface area. So that's something to consider when capturing heat and trying to store it over a duration of time. More heat has to go into a large volume, but it STAYS warm a lot longer. I'm not sure where the perfect balance is there, but I HAVE recently heard from people who had set up gigantic hot water storage tanks for use with their solar hot water (after I made my recent video). Some were 20,000 gallons big and they said that the huge thermal mass allowed them to grab a lot of heat when the sun shone, and to store it for when it wasn't for a long time. One other thing I should mention, and I really don't know how large of a risk this is, but it IS something that I've heard come up from time to time is that legionnaire's disease can grow and thrive in water that is under 140 degrees F. That's why that 140 is a bit of a magic number for water heaters. Again, I don't know how likely that illness is to arise even if conditions favor it, but you might want to look into that a bit to see if you want to keep your water temp lower than 140.

[@PenntuckytheCrag]

Good stuff Praxis

[@aleell6466]

“Hey! Check out this awesome invention I’ve created! Aaaannndd I can make it fart!!” …. I cannot think of anything more quintessentially male steam of consciousness. 😂

[@PraxisPrepper]

If I could design it so it moans seductively, that might be more "quintessentially male" of me???

[@edwinabbel3783]

I have a Winnerwell Nomad woodstove Large with a watertank,.. and i can put kettles on the stove,.. You are doing a great job!! Keep it up!! Greetings from the Netherlands!

[@PraxisPrepper]

Cool setup. This stuff is def fun isn't it!

[@edwinabbel3783]

@@PraxisPrepper indeed,.. I also have Sawyer Waterfilter, Katadyn Pocket Black to prefilter fir my Big Berkey Waterfilter with spare filters,.. And 500 gallons rainbarrels,.. All kinds of fruit trees, berries, grapes and strawberries,.. 1500 cans of CATFOOD,.. 250 pounds of kibble,.. for four years for my 3 cats,... Antibiotics,.. 20.000 rounds of ammo,.. 450 crossbow bolts,... 5 years of food,.. not concidering/ included, garden, scavaning, bartering, hunting gathering or fishing or farmers,.. Going to 7 years soon,.. Thing are geating up,.. Slowly,.... AND THEN ALL once!!!

[@Jilly-Kerry-2Mullens]

I found a rocket mass heater/water heater video I believe I shall build some day.

[@PraxisPrepper]

It's a great idea. Fire produces so much hot water.

[@JTFU]

Urine and fart jokes !! This video has it all.

[@PraxisPrepper]

I always try to cover BOTH of these time honored genres of comedy.

[@allemansratten4281]

I wonder if this could be tied into an in the floor radiant heat system.

[@PraxisPrepper]

I'm sure it could. IN FACT... at my last house build, I had laid the ground work to do just that. Behind the woodstove was a large rock wall. When I built that wall, I laid PEX piping in it like a radiator to pick up heat from the wall (which got quite warm when the woodstove was running). I also laid PEX down under the floor in two large beds of concrete. My plan was to pump the heat down into the floor, but I never got around to finishing hooking it all up before I left to build my new house.

[@ontariohomestead7135]

Did a test system to warm plant trays with aimilar ideas in mind i did a coil of copper right around the stove pipe...two things i learned was i need alot more copper for the coil and recirculating pump also your right a vent is a must

[@PraxisPrepper]

How many feet of copper did you have around the back of the stove? Also my stove (Vermont Castings) is sort of notorious for how much heat it radiates. VC stoves always need much bigger clearances than a lot of other stoves for that reason. Was your stove a similar all iron one like I use? I presume it was. So I'm curious how much copper was too little for you.

[@alschmidt9268]

Why not use an old hotwater tank or two. You would probably take care of you high pressure problem due to the pressure relief valve. A small recirculation pump could be incorporated as well.

[@PraxisPrepper]

That's another method that people have used and the pressure relief valve is critical. For me, I like the fact that (with level of materials knowledge) this is something that I could build myself from the ground up and understand every inch of it. It gives me a lot of satisfaction to build things for myself. But your suggestion is very valid and is (per my research) often times used.

[@Pawpawsplace]

This is awesome. I have been thinking of different ways to heat water in a grid down situation and this was well timed. Thanks. I have seen other systems in the past and this so far is the most viable in my opinion. I might consider adding radiator of some sort to help control the temp of the "Fluid" in the barrel. Or add a whole house circulating system for the hot water. This might emulate "on demand hot water" or an alternate heat source. I don't know just ideas I had while watching this video. Still much to research I think.

[@PraxisPrepper]

I've found out since yesterday that buying a pre-made tank could be a good option as well. Here's one I was eyeing this morning: hydrosolar.ca/products/all-in-one-buffer-tank-and-indirect-water-heater-150-l IDK if I'll still DIY or get a premade tank, but it's all good to ponder over before pulling the trigger.

[@steffankaizer]

great setup but the thermosyphon is necessarily going to stratify the water in the tank. that just means the cold water has to come into the lower end of the spiral to collect the most heat from the hottest water in the top of the tank.

[@PraxisPrepper]

Thanks for your take. I agree. The idea has been evolving ever since I shot this. I actually was able to secure an old used tank that had been used for thermal transfer from a boiler for the tank part. One issue that came up so far is Legionnaire's disease. Given the not-so-hot temps in the tank that are likely with this setup much of the time, it's a perfect breeding ground for that pathogen. It's an additional reason to not have the domestic water be the static water, but rather to only pass through while being warmed.

[@steffankaizer]

@@PraxisPrepper amazing that someone thinks about legionella. it takes only about a day to grow into a whole "legion" lol if the conditions are right. legionella doesnt grow or dies completely in water outside the range 20°C to 55°C depending how far outside this range. everytime it reaches over 60°C you win the war and they have to regrow their numbers ^^ on top of that in your setup the drinkwater is the flowing and will even cool down the boilerwater to below 15°C if the stove is of. be careful with the used tank, if the drinkwater touches surfaces that have been in contact with heating water there are some weird electrochemical effects that can dissolve toxins right out of the metal. i would love to see your new ideas 😁👍

[@PraxisPrepper]

That's a lot to think about there too. The challenge with heading off one's own way and trying things out is needing to keep in mind all the tiny little aspects of a process like this - to be sure nothing comes back to bite one later. I appreciate your sharing your thinking here. I'll share how this project develops as I work on it for sure.@@steffankaizer

[@Forest_Actual]

You could also wrap a copper coil around the stove pipe to heat the water. Thank you!

[@PraxisPrepper]

I see that used a lot too. :)

[@anthonysharp9136]

Another possibility is to locate a temperace tank about a foot over your woodstove if you find one you like the look of (I'm still looking for a stainless tank myself). If it's big enough and/or far enough from the stove, no vent would be needed and you could use it in line with your system.

[@PraxisPrepper]

A simple approach like that sounds cool too - any way to capture and use the heat is great!

[@ironnam8107]

I've been thinking of making a similar heater. Mineral oil is the fluid that I'd use for the heat transfer.

[@PraxisPrepper]

I'll look into that too. I was pondering this last night at 2am when I woke up (pondering projects is one of my favorite ways of not getting enough sleep). I was thinking that it might be good to add stones or scrap metal into the tank as an added heat reservoir. Only issue with that is that if there are the wrong metals mixing together (like if I had copper pipes and also zinc scrap, I'd be building a battery that would start degrading the metal pipes). So that'd be something to consider. But the metal or stone itself could be helpful to capture and hold more thermal energy.

[@ironnam8107]

@@PraxisPrepper mineral oil would eliminate the accidentally battery problem. Stick ferrous metals to help prevent that also. Water would heat up faster. Mineral oil would hold heat longer and could go to a higher then water. No high pressures with oil, still needs vented though. Stones would be more like oil and hold heat longer then metal. If you used them in the tank. It would mostly help keep the temperature in the tank more level, less fluctuations in temperature. The specific heat of generic rock "at a quick glance" doesn't look much higher than oil. Adding stones may not make much difference if you are using mineral oil.

[@PraxisPrepper]

Thanks Ironnam! That's a lot of new ideas to simmer on. I think there are two things for sure that will result from this project. 1, it'll be a way better situation than I have now. 2, I'll figure out things later on after completing it that I could have done that would have been improvements over what I'll end up doing. I've come to feel that perfection is a great thing to aim for, but it always remains a mildly elusive vision and never a captured commodity.@@ironnam8107

[@matthewellisor5835]

I like the recirculating pump idea. How familiar are you with PID controllers?

[@PraxisPrepper]

Since this is the internet, I could find out with a couple of keystrokes, but I'm going to be honest and tell you that my first response to your question was, "What's a PID controller?" Blind guess (given the context of the situation) is that it's some sort of somewhat easily to modify or construct DIY electronic logic circuit creation sort of system whereby I could create my hypothetical "brains" to tell my (equally hypothetical) water pumps described in this video when to turn on and off. Am I close at all?

[@matthewellisor5835]

@@PraxisPrepper Nailed it. It's Proportional Integral Derivative and is commonly utilized to provide a control loop with continuous feedback from the error between the measurement and the setpoint, especially where the hysteresis would otherwise be unacceptably wide.

[@PraxisPrepper]

You lost me after, "Nailed it." LOL. But I'm glad for the suggestion and I'll definitely be familiarizing myself with PID controllers this year. One of the reasons that I early posted this concept was that I presumed people would have some helpful suggestions that might be good for me to integrate early and your controller tip is right inline with what I was anticipating knowledgeable people (such as yourself) who tune into my videos might suggest. So thank you for living well up to my expectations! ;)@@matthewellisor5835

[@thorthunder3227]

You need a lever for water in if it boils off. It would come on and let water in if it got too low.

[@PraxisPrepper]

Good thought. A valve like what refills a toilet tank would be useful for that maybe. Thx for the thought.

[@paperplane1098]

the system we had when I was a boy had no pump. it was convection driven. it was connected directly to the water storage tank via pipes from the top and bottom of the tank. the heat exchange pipes were literally behind a kind of concrete block inside the fireplace. if the fire wasn't going the water didn't flow because no convection. the water going through the stove was the same water that was in the tank. sometimes you could hear the water in the tank boiling. not sure where the pressure went to but there must've been a pressure release for the water to boil. my uncle did engineering work with hot liquids under pressure in the local sugar mill and he built our system without the storage tank I don't think your proposed system would provide much hot water because your heat exchange tank will never exceed 100C (boiling). without the storage tank the cold water has to go through the heat exchange tank quickly (at the pace you're using it). this internet stranger thinks a storage tank is needed.

[@PraxisPrepper]

Hey Paper Plane, it's been a while since you dropped a comment hasn't it? Nice to hear from you. Your thoughts on how much heat can be transferred into the domestic water as it is transiting through the heat reservoir is something that I've wondered about as well. I'm sure there's math that I could to to figure it out, but my sense is to just make sure I put a LOT of copper pipe in that tank so that the water moving through is in there for as long as possible. Thanks for sharing your expereince!

[@bitkrusher5948]

@praxis my water is heated by the wood stove ...we parked a still 10gallons behind the stove abot four inchs above ...and plumbed thru the wall to the sink.....you can fill the still with snow to melt for water and also heat it for washing ...ad water or snow to adjust temp ....stills with out lets work best .dont fill to max always about two thirds volume ...just incase it was to boil .....

[@PraxisPrepper]

That's a cool setup... and it makes me think that I could use a tank-like structure behind my woodstove too (vs. the manifold of pipes I described in this video). So many great options! Thanks for sharing your approach!

[@larryberry2436]

Remember the wise words from Montgomery Scott, “The more they overthink the plumbing, the easier it is to stop up the drain.”

[@PraxisPrepper]

Absolutely, the simpler the better is almost always the case I think.

[@slimdawgwoof]

Please be really careful! It's all fun and games until Praxis gets boiled!

[@AJ-xe7zl]

I would include a refill inlet controlled by a float to ensure your heat tank always has water to heat.

[@PraxisPrepper]

Yeah some sort of way of visually keeping an eye on the tank fluid level would be a good idea.

[@IvanNedostal]

You can eliminate electricity / pump / controller altogether, just by positioning water tank on higher level then fireplace is on. Operating word here is : Thermosiphon. It works because of gravity and water changing density upon heating, 80+% middle east heats water with systems utilizing this effect, but in different context. Of course you still need vent, but that can be mechanical thing.

[@IvanNedostal]

For fireplace heater part. For other part, electric heater, plumbing part - your assumptions are all correct.

[@PraxisPrepper]

Thanks for your take on this. One of the reasons I released this video fresh yesterday was that I knew a lot of smart people who watch my channel (such as yourself) would have some excellent helpful insights. My tank height is a bit mandated by where I'm going to be placing it, but I understand the goal of getting some height for that thermal siphoning effect. If I CAN get that working enough, the circulator pump (which wouldn't be necessarily silent) can hopefully be avoided.

[@IvanNedostal]

@@PraxisPrepper Yeah, just by placing tank little higher you can have hot water without pv/electricity. So immediately as i saw your plan i had to say something. I am more finnish masonry heater with old cast iron radiator embedded inside as a heat exchanger, kinda guy myself (it had to be build same time as a house). :) Have a nice day.

[@PraxisPrepper]

If I were to build again I think I'd definitely do something along the lines that you mentioned you'd done. At my last build, I actually had run pex tubing snaking back and forth through a stone wall immediately behind my woodstove to capture heat. The plan had been to pump water warmed in those tubes down into other tubes I'd buried in the floor, but I never got around to finishing the system before I left.@@IvanNedostal

[@MosaicHomestead]

The plastic tank won't work, a metal tank will work better, get a hot water pressure valve and go with direct hot water in the tank, I don't think water will get to boiling if radiator isn't in direct contact with fire.

[@matthewgardner4532]

Find your self an inexpensive Indirect HWT.

[@PraxisPrepper]

But then I wouldn't have the fun of building this thing! But you're right that I could maybe make this project even easier and possibly more efficient if I went with a prebuilt unit. I'll ponder that option.

[@preppingforprophecy7680]

No pump is needed, if plastic drum is raised high enough to gravity feed the heat collector.......

[@PraxisPrepper]

I'd like it if the pump is unnecessary. The best convection will happen when the thermal differential is high, but not so much when it's not so high. I'll find out and share what I learn on here.

[@MosaicHomestead]

You can get a stainless steel tank.

[@PraxisPrepper]

I can. I'm wondering why you think the steel tank would be better though? I know steel is easy for you to work with given your skill set, but it's harder for me (with mine). That's not a reason for me to go with something inferior, but it IS a reason for me to wobble one way or the other if all other things are equal. Are there advantages to steel that I'm not considering? I'm planning to insulate the tank anyhow, but one advantage of plastic is that the plastic itself insulates a bit too. I'd be curious about your thoughts (as you might imagine I would be).

[@MosaicHomestead]

@PraxisPrepper you get stainless steel, use the manufactured holes for in and out, place drum on its side. The threads are 2 inch if not mistaken, reduce to size needed...place hot water safety pressure valve on hot water pipe coming out of tank, all this should be metal.

[@markstahovic9226]

Kinda sorta like no problem or do it this way or maybe not u gloss over a lot of problems when someone builds something u hafo be exact or it won't work

[@PraxisPrepper]

This isn't a building video, or a proof of concept video. This is just an initial concept video. It's part of the process, so I think it's good to share that with people.

[@JTFU]

For a 50 gallon tank, that’s approximately 500 times urinating cycles. Depending on bladder size and beer consumption. Could get costly. Maybe antifreeze.

[@701overland]

first

[@PraxisPrepper]

You know what makes me pretty buzzed lately - is that several people lately have bothered to leave a "first" comment. I think one's channel has to get to a certain level of regard before anyone even cares if they were first; and NO ONE used to write "first" on my videos before a few months ago. So that's progress. :) Congrats, I find that I'm pretty much never first even when I get to a video within the first few minutes of it being released.

[@nills2gills811]

I believe theres is an error in the fact that we know thermosiphons work by making hot water, and capturing on the physics principle that hotter water is less dense therefore it will rise. I think that your hot and cold water inlets onto your little side jacuzzi are about the same elevation. This will confuse the hot water about which way to go. The cold water inlet on the salt jacuzzi should be gravity fed to the lower portion of the tank so that when it heats it exits on the top and it doesnt try to rise in both directions and terminate or slow the flow. To me if you are capable of installing a circuitboard that controls the pump on the tubing then you could also control an electric valve that shuts off flow at certain temp. Anyone feel free to expand on this.

[@PraxisPrepper]

If I drew it that way, (the outlets at the same height) in my drawing, you're correct that it wouldn't work. Thx for pointing that out to try to catch it for me (and others reading these comments). I wasn't going to build it that way, but if I WAS, you'd have saved me from a certain failure. The project has changed a little since this video. I was able to find a 2nd hand used thermo-transfer tank. So that part is all done. One thing that I've learned from my research is that there is an additional reason to NOT have the domestic water be used as the heat reservoir itself. That wasn't the way I was drawing it in here (for the purpose of not having to have the reservoir be under pressure), but I discovered that doing so would ALSO create the opportunity for legionnaire's disease to grow in the tank and then be spread into the water supply. So that's an extra reason I found out too. Thx for sharing your comment!