Unused water heater, leave full or empty?

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A friend has a house that came with two identical water heaters hooked up in parallel. He doesn't need all the capacity, so we turned one of them off and turned off the water going into it. This was several years ago. The water heater was about 4 years old at the time, it's now 7 years old.
Given that a tank has already had some service, what would you guys do to try to keep the spare tank available for as long as possible?
Leave it full of water?
Drain it?
My thought was that draining it would be worse, because allowing air in, it would rust.......
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I think you're right about the rust. Can you alternate them, every couple months?
Not sure that makes any sense, but it's a thought.
Christopher A. Young Learn more about Jesus www.lds.org .
A friend has a house that came with two identical water heaters hooked up in parallel. He doesn't need all the capacity, so we turned one of them off and turned off the water going into it. This was several years ago. The water heater was about 4 years old at the time, it's now 7 years old.
Given that a tank has already had some service, what would you guys do to try to keep the spare tank available for as long as possible?
Leave it full of water?
Drain it?
My thought was that draining it would be worse, because allowing air in, it would rust.......
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Fill it with water, add a rust inhibitor?
As an aside, shouldn't two water heaters be hooked up in series? Been meaning to post that to the group. The rcm peeple should have some insights into both Qs.
--
EA



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Drain it fully, blow out any remaining water with compressed air, purge with heated dry air until you get no condensation whatsoever on a chilled mirror and ideally finally purge with dry nitrogen and seal.
Most rust inhibitors are to some degree toxic so you dont want to use them in the tank if it will be used for kitchen or bathroom hot water unless they are specifcally marketed as non-toxic for food processig plant. If you water-fill it, ideally use boiled water to reduce dissolved oxygen.
--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
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On 2/3/2013 9:11 AM, Ian Malcolm wrote:

Dissolved oxygen? In H20?
--
Robert Allison
New Braunfels, TX
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Well, sure. Fish, after all, couldn't survive without it.
But as for drying the tank out with heated dry air and filling it with nitrogen, somehow I don't think that is going to happen.....

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gun to one of the ports of the tank and leave another port open. Don't turn it up to its full paint-stripping setting! ;-)
I *KNOW* the dry nitrogen is unlikely to be convenient. . . .
--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
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wrote:

Well, it is offered to auto buffs for whom nothing is too good for Nelly -- and to whom chemistry is still a mystery.... lol http://www.quadratec.com/products/92042_9103.htm?sgsc Z06ZR1C6Z06ZR1&utm_medium=compshop&utm_source=googlemerchant&gclid=CMaxjsuGm7UCFUWo4AodIHoAIA
--
EA


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More accurately, dissolved air.
Christopher A. Young Learn more about Jesus www.lds.org .
On 2/3/2013 9:11 AM, Ian Malcolm wrote:

Dissolved oxygen? In H20?
--
Robert Allison
New Braunfels, TX
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Draw some hot water into a glass. The slowly disappearing milkiness is tiny bubbles of air that comes out of solution when the pressure is removed. Cold water holds more dissolved air than hot water.
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I acquired a serviceable used electric water heater from a remodelling project and mounted it horizontally in a close-fitted greenhouse box as an unpressurized solar batch heater. After about 3-4 years the tank started to spring small leaks on the cold bottom side which I patched until I couldn't keep up.
Anything you put in it, like RV antifreeze, will be very tricky to completely remove because the tanks are so hard to handle. The best way I found was hanging it horizontal by a choker sling with the heater holes on the bottom and spraying a hose in through them, but I doubt I directly rinsed even half of the surface area and couldn't touch anything absorbed into the crud in the vee groove around the concave bottom end. Since the tank wasn't connected to my plumbing and the water was only for laundry or car washing a little soap or LPS-3 in it didn't matter.
They can be difficult/expensive to dispose of unless you have a friend in the scrap business. I traded two heaters for an old farm wagon front axle.
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The issue of series vs parallel connection of dual water heaters has been debated here a few times. AFAIK, there wasn't any overwhelming advantage to either. One difference would be that in parallel as soon as you've drawn some amount of water, they are BOTH going to fire, so you're getting 2X the heating sooner. With them in series, the upstream one isn't going to fire until a lot of the water has been drawn.
On the other hand, with them in series there is going to be more hot water at a higher temp for longer due to cold water not coming directly into the upstream tank. In the grand scheme of things, it probably doesn't make much difference.
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Having a second tank that's unpowered, uninsulated, and plumbed in series so that cold water passes through it first will reduce summertime AC and water heating costs by naturally warming the inlet water up to room temp.
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In rec.crafts.metalworking PrecisionmachinisT

Other than skinning a trashed water heater, most of which are leaking anyways, are there purpose made tanks for this use? I've been looking for something along these lines to get "room temp" water for a photographic darkroom where there's extended draw of water.
Anything homemade looking and attached to the water lines before the backflow preventers might draw attention from the landlord or inspectors. Just adding a waterheater-ish tank before the existing one would be the easiest, as long as it draw no attention and won't burst over the weekend.
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On Mon, 4 Feb 2013 19:38:59 +0000 (UTC), Cydrome Leader

You could get a water heater that's being replaced before it bursts. Just add a valve on its inlet side so there is no pressure on it when it's not in use. It should last a long time without constant pressure on it. If it does leak, you're right there.
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I got nowhere by asking a plumbing supply house this question. The owner thought it was a good idea but couldn't find an inexpensive tank in his catalog.
The two best possibilities I can think of are a bladder tank for a well and a water softener tank. http://www.wwpp.com/products/flexcon-fiberglass-tanks/flexcon-fiberglass-pressure-tanks.htm http://www.discountwatersofteners.com/softener-parts/resin-tanks.html
Though they won't take much pressure, a blue plastic 55 gallon barrel is a cheap option for the rinse water. I have one hung high in a shed at the back of my large lot for brush fire protection. The larger bung plug has a knockout for 3/4" NPT. ~5 PSI bulges the bottom enough to make it tip over. jsw
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On Mon, 4 Feb 2013 19:38:59 +0000 (UTC)
<snip>

We have something like 150 ft of 1 inch black plastic water pipe in a coil (maybe 3 ft in diameter), hanging on the wall downstairs before the toilet supply. Does wonders in the summer time when they would sweat otherwise. Used to have a galvanized water pressure tank for same years ago but due to hard water it developed a lot of sediment. So far the coiled up pipe seems to be working okay, maybe 20 years now.
--
Leon Fisk
Grand Rapids MI/Zone 5b
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wrote:

Putting that coil outside in the sun would be even better, in the summer. Solar on the cheap.... Or in a black box, covered by glass..... really good solar, on the cheap....
Toward the purpose-made tank Q: An old compressor tank, 30-50 gals? Or smaller ones in series? Even propane? Altho the fittings on propane are an experience to remove.... May want to paint the interior first.
--
EA


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On 2/5/2013 3:27 PM, Existential Angst wrote:

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wrote:

Certainly..... who wants cold water splashing on their ass?? sheeesh.....
--
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