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Old 28-03-2018, 17:40   #1
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12V water tank heater

I live aboard in Alaska, and I would like my water tank">fresh water tank (aluminum, around 40 gallons) to not be so chilly. Is there some kind of 12V, drinking water safe heater that I could put in the tank and keep it from freezing, and maybe raise it to 50 degrees or so?
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Old 28-03-2018, 17:50   #2
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Re: 12V water tank heater

There are HWS tanks designed for electric heating elements.

And there are 12V heating elements, at least I've seen dual AC/DC ones.

The 12V ones don't put out much power compared to mains, but of course they'll drain a bank quick, best to only run while charging.
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Old 28-03-2018, 17:58   #3
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Re: 12V water tank heater

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And there are 12V heating elements, at least I've seen dual AC/DC ones.
I think you mean the kind that heats water up to 125 degrees for taking a shower? That's not what I want. I want a low-power heater, designed only to keep the water from freezing and warm it up just a little. I've seen some for RV's that stick onto the outside of a tank... just wondering if there's a kind that goes inside. I'm sure that would be more efficient, and I'm on solar power.
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Old 28-03-2018, 18:07   #4
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Re: 12V water tank heater

He's not looking for a water heater, he's looking for a water warmer...and I'm thinkin' MAYBE a bilge heater might be the answer. Where's the water tank located in the boat?
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Old 28-03-2018, 18:13   #5
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Re: 12V water tank heater

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I'm thinkin' MAYBE a bilge heater might be the answer. Where's the water tank located in the boat?
Port quarter, right next to the engine. When you say bilge heater, do you mean the thing that blows warm air around? The stick-on tank heaters would be more efficient than that...
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Old 28-03-2018, 18:15   #6
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Re: 12V water tank heater

Atwood in the states make a 12 volt, 110 Volt and a 240 volt heater elements that go inside a tank,
My 6 gallon tank had 110 volts and also heated from the motor,
I was thinking of changing the elements to 12 volt, But wasnt sure if it would heat the water sufficiently,
I no longer have 110 volts on my boat, Only 12 volt and 240 volts,

The tank gets heated from the motor sufficiently, and being in the tropics its not really needed,
I can run the motor for 10 minutes if I really need a hot shower,
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Old 28-03-2018, 18:46   #7
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Re: 12V water tank heater

Yes the 12V elements would take forever to get a tank of cold water warm, forget about hot.

Easy enough to put a switch on it, either manual or thermostatically controlled, set to whatever you want.

But even something very low watts can drain the batts, again put a VSR on it so only runs while you're charging.
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Old 28-03-2018, 18:49   #8
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Re: 12V water tank heater

If you have 120vac available
a magnetic engine heater ZeroStartâ„¢ Super Heat Magnet | Canadian Tire

or a cold weather battery warming blanket may work.


Can I ask why you need to warm your drinking water?

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Old 29-03-2018, 08:08   #9
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Re: 12V water tank heater

Mines a $300 gadget called Duoetto
It runs off AC or 12v, has its own internal 10 Gall tank
I think later models switch automatically

You can control temperature from near boiling, certainly too hot to keep your hands in, via an adjustment knob seen on the front, or via a mixer system requiring a pressure water system.
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Old 29-03-2018, 08:26   #10
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Re: 12V water tank heater

I like the Duoetto, but they only distribute to Australia and New Zealand .... I'm in the USA.

I've read of a 12 volt element that can be installed in the drain plug location of a hot water tank, to warm the water. For a 40 gallon tank, this is only going to be a minimal amount of warming, but I bet would stop it from freezing? It would take some amps, probably all the time, to maintain even a very low temperature, with that much water mass...

See:
Missouri Wind and Solar
Submersible DC Water Heater Elements - Missouri Wind and Solar
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Old 29-03-2018, 08:28   #11
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Re: 12V water tank heater

Truck mirrors, the big one on semi's are heated with a 12v stick on resistor grid. Perhaps you could stick one on your water tank and cover with some insulation. I'd also want some sort of safety to make sure you don't pull your 12v supply down too far. Perhaps an independent solar panel could power the heater.
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Old 29-03-2018, 08:39   #12
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Re: 12V water tank heater

Sounds like you’re looking for a 12v immersion element like this:
https://www.amazon.ca/Dernord-Immers.../dp/B0761L2Q8M
Maybe choose a low wattage unit and run on a timer?
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Old 29-03-2018, 08:50   #13
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Re: 12V water tank heater

Heating 40 gallons of water from just above freezing to 50 F requires 6,000 BTUs. To figure out how many watts of electric power that would take, you have to plug in the elapsed time. For example, if you could achieve 100% efficiency, you could heat 40 gallons 18 degrees in an hour with about 1,800 watts.
Of course, there's no such thing as 100% efficiency, you also have to figure in rate of heat losses.

You said you've got solar power, but gave no details, but guessing you don't have a spare 1.8 kw
You could try a super-cheap approach, get a 12 volt electric car blanket, like this one:


It's only 50 watts, it might take a week or two of sunny days to do the job, and you'd have to place it under/around the tank, but worth a shot.

Of course, you should insulate the tank as much as possible...
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Old 29-03-2018, 09:32   #14
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Re: 12V water tank heater

Quote:
Originally Posted by Water Dragon View Post
I think you mean the kind that heats water up to 125 degrees for taking a shower? That's not what I want. I want a low-power heater, designed only to keep the water from freezing and warm it up just a little. I've seen some for RV's that stick onto the outside of a tank... just wondering if there's a kind that goes inside. I'm sure that would be more efficient, and I'm on solar power.
Look at farm and ranch supply outfits. Farmers and ranchers have the same issue, keeping the water trough from freezing. Most of their options will be 12v you can pick your amperage.
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Old 29-03-2018, 09:50   #15
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Re: 12V water tank heater

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Originally Posted by RobinScurr View Post
I like the Duoetto, but they only distribute to Australia and New Zealand .... I'm in the USA.

I've read of a 12 volt element that can be installed in the drain plug location of a hot water tank, to warm the water. For a 40 gallon tank, this is only going to be a minimal amount of warming, but I bet would stop it from freezing? It would take some amps, probably all the time, to maintain even a very low temperature, with that much water mass...

See:
Missouri Wind and Solar
Submersible DC Water Heater Elements - Missouri Wind and Solar
I reckon if I wasnt disposed to buying stuff on ebay from Au, Id be looking at an aquarium heater. The kind of thing thats in a sort of test tube and has some sort of temp regulator on it.

Cheap and cheerful to organise, sealed and hygienic, if you get something small to minimise the current draw it wont ever get to the set temp on the thermostat but it would stop your water from freezing.

I think those hydroponics guys use the same sort of thing
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