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.......
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.
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.
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.
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.
I don't know the answer, but given the choice, I think I would drain it. My thinking would be to drain it and leave the drain valve open to hopefully let it completely dry out over time.
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.
I would put them in series using the inactive heater as a tempering tank but it would need to be drained on a schedule too as I think it could catch some sediment from the incoming water. It would be available as a ready backup and not that hard to bypass the other heater if/when it failed. Assuming it a gas fired unit, it could be left on on a low setting to keep the burners moisture and insect free. ^_^
Not really a problem if you can adapt the nozzle of an electric hot air 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. . . .
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.
Rust and what the anode is there for are two seperate things. Rust involves oxygen combining with iron. The sacrificial anode involves two dissimilar metals in an electrolyte. Think about boats. They use a similar approach, with zinc being used as the sacrificial anode to protect the underwater metals. Zinc is more reactive than bronze, stainless steel, etc so it comes off instead.
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.
I am not sure, but I think that technically speaking that approach won't save any money on energy costs. The reason is that for the water in the first tank to be brought up to room temperature, it needs to draw its heat energy from the room. So, it will cost that much more to heat the room because some of the room heat is going toward heating the water in the first tank. In other words, there is no free heat -- it either gets its heat from being heated by at working hot water tank, or it gets its heat from the room and that heat energy needs to be replaced by the heating system for the room.
On Monday, February 4, 2013 2:56:03 PM UTC-5, TomR wrote:
ote in message > news:510e79e9$0$9808$ snipped-for-privacy@cv.net... >> wrote in message >> news:8b56815a-8209-4c99-b3fb-435202725549@5g20=
00yqz.googlegroups.com... >>> A friend has a house that came with two ident= ical water >>> heaters hooked up in parallel. He doesn't need all the capac= ity, >>> so we turned one of them off and turned off the water going >>> in= to it. This was several years ago. The water heater was >>> about 4 years o= ld 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, beca= use >>> allowing air in, it would rust....... >>> >>> >> >> Fill it with wa= ter, add a rust inhibitor? >> >> As an aside, shouldn't two water heaters b= e hooked up in series? >> Been meaning to post that to the group. The rcm p= eeple should have >> some insights into both Qs. > Having a second tank tha= t's unpowered, uninsulated, and plumbed in > series so that cold water pass= es through it first will reduce > summertime AC and water heating costs by = naturally warming the inlet > water up to room temp. I am not sure, but I t= hink that technically speaking that approach won't save any money on energy= costs. The reason is that for the water in the first tank to be brought up= to room temperature, it needs to draw its heat energy from the room. So, i= t will cost that much more to heat the room because some of the room heat i= s going toward heating the water in the first tank. In other words, there i= s no free heat -- it either gets its heat from being heated by at working h= ot water tank, or it gets its heat from the room and that heat energy needs= to be replaced by the heating system for the room.
I believe he said "reduce summer time costs". And it does do that since gr= ound water and city water are usually a lot cooler than summer air temps.
I run two wh in series with the 1st one on a 30amp switch in the hall. Whe= n I anticipate guests or otherwise needing extra hw I just turn it on.
000yqz.googlegroups.com... >>> A friend has a house that came with two iden= tical water >>> heaters hooked up in parallel. He doesn't need all the capa= city, >>> so we turned one of them off and turned off the water going >>> i= nto 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 alread= y had some service, what would >>> you guys do to try to keep the spare tan= k available for as long >>> as possible? >>> >>> Leave it full of water? >>=
ause >>> allowing air in, it would rust....... >>> >>> >> >> Fill it with w= ater, 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. > Having a second tank th= at's unpowered, uninsulated, and plumbed in > series so that cold water pas= ses through it first will reduce > summertime AC and water heating costs by= naturally warming the inlet > water up to room temp. I am not sure, but I = think that technically speaking that approach won't save any money on energ= y costs. The reason is that for the water in the first tank to be brought u= p to room temperature, it needs to draw its heat energy from the room. So, = it will cost that much more to heat the room because some of the room heat = is going toward heating the water in the first tank. In other words, there = is no free heat -- it either gets its heat from being heated by at working = hot water tank, or it gets its heat from the room and that heat energy need= s to be replaced by the heating system for the room.
e ground water and city water are usually a lot cooler than summer air temp= s.
But the proposed tank isn't going to be sitting outside in the summer air. It's typically going to be in an unfinished basement, or inside the living space. So, if you take city water at 45F in winter and get it up to 60F in a basement, I guess it will help some, but doubt it's worth the trouble. In summer it would make even less difference, because the incoming city water is going to be closer to basement or living space temp.
For the guy asking if there are tanks suitable for the purpose, that would seem to be any water tank that's suited for a well pump. Preferably without a bladder inside, but that could be removed. Might find one on craigslist....
=A0When I anticipate guests or otherwise needing extra hw I just turn it on= .
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