Pitfalls of a diy electric water heater?

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Apropos of the recent thread on tankless heaters, is a diy tank-type electric water heater feasible? 100 gal or so propane tank? Might have to epoxy paint the inside or sumpn. 'course, a little rust never hurt anybody.... Theoretically, this tank could last pert near forever.
--
EA




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This smells like a troll-ish post man...
A hot water tank "painted" with epoxy paint would fail quickly...
You need to be able to apply a glass lining bonded to the steel tank -- that sounds fairly impossible to do at home through the filling port on a 100 gallon propane tank...
Also you would need an input and an output as well as a fixture for the anode rod...
It is not something you can successfully make at home, pit corrosion will quickly eat through ANY imperfection in a homemade tank... As water is heated its pressure increases, so a corroded tank would eventually fail by bursting...
~~ Evan
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wrote:

This smells like a troll-ish post man... -------------------------------------- Based on.....? And you define troll-ish how??
A hot water tank "painted" with epoxy paint would fail quickly...
You need to be able to apply a glass lining bonded to the steel tank -- that sounds fairly impossible to do at home through the filling port on a 100 gallon propane tank... ------------------------------------------------- Modern epoxies are perty sophisticated. Might even have some advantages over glass linings. Lifespans of current tank heaters are 5-10 years, altho mine is on 15 years, poss. due to magnesium strips I have clamped in various places. Seems to me epoxy could last that long, and then it might also be pretty easy to re-coat.
Also you would need an input and an output as well as a fixture for the anode rod... ------------------------------------------------------ Dats why god invented welding and weldable plumbing fittings.
It is not something you can successfully make at home, pit corrosion will quickly eat through ANY imperfection in a homemade tank... As water is heated its pressure increases, so a corroded tank would eventually fail by bursting... ------------------------------------------------------- Water tanks don't explosively burst, air tanks do. Water is for all intents and purposes incompressible, and the vast majority of its pressure is the city water pressure or well pump pressure.
As far as corrosion goes, that depends on how far along epoxy coatings have come.
Heh, and stainless should solve all these problems, altho god knows what the initial cost would be. I'll bet, tho, a steel shop that could roll 1/8 SS sheet could weld up sumpn serviceable for a reasonable shop charge above material cost. What's SS, $2-4 per pound? a 4x8 sheet weighs about 180#. Mebbe $500 for the sheet, mebbe that much for the rolling, welding? For a forever forever tank.
Also, a heavily anodized alum tank is a possibility -- altho admittedly we are straying from the diy premise.
--
EA




~~ Evan



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Existential Angst wrote: (...)

You say that like straying is a *bad* thing:
http://www.youtube.com/watch?v=0kOhyNK-jaM

--Winston
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Water tanks don't explosively burst *anymore* unless you purposefully disable the emergency pressure relief valve...
If you did that and the tank overheated it can and *will* burst with enough force to propel the tank upwards through several floors of typical residential construction...
That is why hot water heaters have required safety relief valves these days...
So building your own tank DIY is a risky procedure and then you wouldn't be able to install it in a dwelling without having it UL tested and approved...
BTW: If epoxy was a practical method of lining hot water tanks it would be being used... Glass is generally much more inert than other materials, which is why it is used to store many various chemicals in laboratory settings... Tons of chemistry going on in your water -- it isn't just H2O, there are plenty of cations and anions dissolved in solution in drinking water...
~~ Evan
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How "hot" is that water you're heating?
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OK, msybe I'm missing something, but... Without closing the inlet valve, how can the internal pressure of the tank exceed the inlet water pressure?
I have had a water heater (gas fired) fail catastrophically. It was a most impressive geyser erupting out of the flue pipe, but certainly nothing that would qualify as an "explosion." Good thing that I was home at the time and was able to shut it off before even more water landed on the floor.
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The guys that did it on that show filled the tank, put plugs in all the inlets/outlets, and disabled the thermostats. The applied power and waited.
Epoxy is pretty good these days and you might make one work for the same life expectancy of a commercail one. But by the time you weld on some more bung holes, buy epoxy, buy the heating elements and thermostats, insulate it, it will cost more than picking one up at Lowes.
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there are stainless steel non magnetic tanks available they should last forever since non magnetic stanless doesnt rust, but they cost a fortune, the payback is forever.
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since the tank in question is electric lets say a new commercial 12 year warranty tank is 500 bucks and lasts 12 years although longer life is normal.
Thats under 42 bucks a year, or $3.50 per month. less than a decent candy bar a week.
To extend the life of any water heater install a ball type drain valve to minimize crud build up in tank and install premium anodes and replace every couple years.
This might get yu 20 years out of a tank, but I doubt its woth the effort.......
At one time sears sold water heaters made with plastic tanks with a lifetime guarantee. I was told the plastic tanks got brittle with age and eventually failed.
WW Grainger may still sell them...
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The heater elements burn out like any other and cost about $50 to replace. Since the tank is insulated plastic the thermostat senses the water temperature through the 1.5" diameter solid brass plug on the special element.
jsw
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many municipalties require anti siphon valves on the main water entrance, or water wells.
in either case a overheated tank could burst if it lacked the T&P valve
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An antisiphon will discharge water if the down side develops more pressure than the supply. Most areas I have seen require some combination of a check valve and/or a small pressure tank on the hw system. They only require an antisiphon on irrigation around here.
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On 5/9/2011 7:28 AM, rangerssuck wrote:

Backflow prevention is a common requirement. So if no water is being used the internal house pressure will rise above the street pressure. That is the reason every water heater I have ever seen includes the requirement "thermal expansion means must be installed". That really helps extend the tank life.

Me too, fortunately in both cases I was home. The last time I just returned from a trip and used the toliet. After quite some time I could still hear water running and thought it was the toilet. I checked that and then discovered the heater tank had failed and there was a large stream of water squirting against the wall.
As the other poster noted water is incompressible so the only way to get an explosive failure would be to have no safety valve (or a failed one) and a burner runaway superheating the water.
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Guess that's one reason to be happy my hw tank is in the garage.
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Evan wrote:

Great! We were waiting for him to complain bitterly, when it leaked rusty water all over the place. :(
--
You can't fix stupid. You can't even put a Band-Aid on it, because it's
Teflon coated.
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Michael A. Terrell wrote:

Well, we could wait for him to Darwinize himself. >:->
Cheers! Rich
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wrote:

There are thousands of tanks in service for various water uses that have no glass lining. Steam boilers have no glass lining either. You may get rust, but with a thick wall, it can last decades with no lining.

It will leak, eventually, but with a pressure relive valve, it will not burst.
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wrote:

Some of that may be due to water treatment of boilers, but then many aren't treated. Potable water can't really be treated.
--
EA

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I can be done, I'm just not sure how practical it would be. Coating the inside is a "must" to prevent rust, but I don't know how well that can be done, given the little access to the interior. You could probably pour in some liquid and roll it around.
Then you need a few holes. Inlet, outlet, safety valve, heating elements, drain. Mount and electrical box, of course.
I bet it has been done by someone, someplace, just for the fun of it.
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