I’d like to make a water heater using a TLUD heat source, with an old propane tank for the water. Do any of you have experience with water in propane tanks? Am I setting up to produce rust? Is there a paint or coating that would stop the rust but be drinking water safe?
Thanks in advance . . .
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If you gonna use it for drinking water there are two options in my opinion, stainless or emaile.
Next to keep the rust away, make sure oxigen cant enter, so closed system. Be carefull about the safety features, but I dont have to teach you that 
. You are a clever guy.
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Depends on what scale you are doing. Kelly Kettle for heating water are very hard to beat.
But I use a DIY Solo stove myself. All depends on the volume of water you want to heat.
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Propane tanks have a lining to add that rotten egg smell, so I’m assuming it would also do that to any water inside the tank.
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You shouldn’t drink hot water anyway. The main reason is it dissolves chemicals especially lead faster. Propane tanks rust out. And the bacteria that produce the sulfur smell in water that feed off iron are anaerobic.
I would use a heat exchanger to keep the water separate if you are going to use a hot water tank. namely to keep the water separate but also because the heater isn’t going to be running the -whole- time, and the circulating pump can be shut off when not needed.
ALSO be VERY careful, the water can get too hot and cause scalding.
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Hi Kent,
I would suggest you find an old gas fired hot water heater, ‘b-vent’ type, on craigslist. They usually have some on there for free. You could keep the insulation in place if appropriate. They have a pipe up their center where heat is actually transferred. Inside the the center pipe there is usually a twisted piece of metal, called a spinner, that increases heat transfer. Most of them have a sacrificial zinc anode that reduces corrosion. They also have a safety valve, which is VERY important.
Rindert
Example listing:
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I have two different tanks for my hot water floors. One for the upstairs and one for the downstairs. One is a large oxygen tank and the other is a hundred pound propane tank. I wouldn’t drink the water running through them but I have been storing hot water in them for 22 years now. I drain them when the heating season is over and the water is a little rusty. I’m sure it’s a race to see which of us bites it first and I’m sure that if it’s the tanks it will be in January. If I were a betting man I’d bet that the tanks will outlast me. Of course the tanks themselves are not exposed to high heat like you would get in a TLUD. The water is heated in pipe grids and thermosyphons up to the tanks.
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Thank you all for the ideas and cautions. In order of appearance:
Stainless would be great; what’s emaile?
Kelly Kettles I really like, for water I’d actually drink. When I said “drinking water,” I probably should have said “bathing water.” It should be clean enough not to be a health risk when washing. The goal is a small, wood-fired shower for use when the power’s out, or too expensive.
Good thing to consider. I thought the odor was in the propane. I’ll have to check that out.
Yeah, probably no drinking, but maybe bathing. One benefit of a TLUD is batch operation. I hope to use a measured fuel amount to raise the temperature of the water a proportional amount. Well below boiling is fine, but maybe hot enough to require some additional cold water to raise the total volume for a longer shower 
I have an inexpensive, small 12 volt “sprayer” pump, not made in USA, that I plan to try. The tank will be open to atmosphere, so no steam explosions.
Good idea. I looked a little on craigslist a while back, but not very consistently. They tend to be scarce here is the land of cheap hydropower. No natural gas here with the lower population density, and propane winds up more expensive I think. I’ve salvaged a bunch of “barbeque” tanks for gasifiers (and a kettle corn cooker), so that’s why I asked the question.
Aha! An encouraging word. Thanks, Tom. I think I’ll give it a try when time allows, and if it fails, the cost is small compared to the education.
Thanks again, everyone!
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Hi, Kent! I was just thinking about this water heating subject, and I remembered our own Dan H did this years ago. Here is a link to the video he posted. the description of the video on YouTube has some details of the build.
[Wood fired domestic hot water heater ]
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Thanks, Mike (and @dynamodan). That’s what I’d like long term. Our current water heater (electric) is between the attached garage and kitchen, near the center of the house. Fine with electricity, not not convenient for wood with the need for air and a stove pipe. I may, someday, try something more serious like Dan’s just outside the house as a preheater, and connect it to the existing system with pex. Not today, probably not tomorrow, but someday, maybe
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I believe emalie is enamel.
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Like a fired-on enamel? I think that would be great, but I think it’s probably beyond my skills.
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Yes, fire-on enamel. @Pelletpower Joep can chime in in case he meant something else.
I think you would have to be incredibly lucky to find an enameled tank in the size you need
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Thanks Johan, yes.
But I dont know what Kents plans are with the water, heating the house or taking a shower?
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Finally a question I can answer: taking a shower
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Take solar tubing in the watertank. The pipe is stainless and affordable, has a big surface etc etc. And you can make you tank from whatever material you want. Just an idea.
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Kent, l got mine custom made. The builder presented me with a couple of options. Food grade paint like coating, stainless… from experiances l know l dont trust paint, and stainless is prone to cracking after some heat cycles. Then he came up with a near forgoten technick in the boiler world, zinc plating. Im super pleased with it. Been in dayly use for 3 years now and not long ago l opened it, its like new inside.
Also no scale, the water never gets above 70c and the heating flue is large area/low temp so its as clean as new. Highly recomend.
Edit: its cheap too. Last time l remember was around 1€ per kilo of material.
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Thank you Kristijan. I suspect your tank is hot dipped galvanized. That’s probably beyond my ability, but I might be able to electroplate with zinc.
My son had a good suggestion I might try first: a TLUD flash heater. We need to think of a way to regulate the maximum temperature so we don’t build a flash boiler
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