Will draining a hot water heater tank preserve its life?


I heat my water for washing with natural gas. I have both a tank type water heater and a tankless water heater. They both sit in the basement under my living room. I can easily switch to either using one of them or both of them to heat my water. During the summer the tankless is sufficient for my needs but not in the winter when the incoming water is very cold. Does it pay to completely drain the tank heater during the warmer months of the year when I will not use it or will it corrode more than with water in it? Richard
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I'd keep some flow going through the tank so it will not get all icky inside from sitting. IMO, it would be better to leave the water in it and just turn the heat off of it.
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In winter feed water: in from supply, tankless, tank heater, fixtures.
in summewr reverse this so incoming water first goes thru non heated tank heater : in from supply, tank heater heater off, tankless, fixtures.
just a few valves can do this easily. I would keep the water flowing thru that tank at all times
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If my drawings are correct you need 6 valves to do this, in addition to 6 tees. Richard
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On 5 Mar 2007 08:35:43 -0800, " snipped-for-privacy@gmail.com"

I was brought up to speed on my water heater life, by a handy man. He said stressing out the heater could shorten the life. Example, having the termistat very high, and letting muck build up in the bottom.
Do you think letting out the water and letting air come in contact with the inner lining is stress?
Tom @ www.NoCostAds.com
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I would drain the tank, and shut off the pilot light. Having water sit will only allow for the tank to corrode.
--
Roger Shoaf
If you are not part of the solution, you are not dissolved in the solvent.
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Rust requires moisture and air. A empty tank is the perfect environment for fast rusting:(
Much better to leave water fl;owing with pilot off
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I think I would keep the conventional water heater inserted BEFORE the tankless. In the coldest months, have the conventional turned on and set to the lowest temp. In summer, just turn if off. That will yield the lowest heat loss from the conventional tank while solving the incoming cold water problem. I would share the concerns echoed by those saying draining the tank may be worse as far as promoting rust.
Out of curiousity, how did you wind up with a tankless that is not adequate to serve your full needs? Using both would seem to be the worst combo. A tankless costs so much more, it will take a long time to recover the upfront cost to begin with. And with your setup, you still have the cost of replacing a regular unit, some heat loss from it, etc.
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On Mar 7, 12:36 pm, snipped-for-privacy@optonline.net wrote:

When I bought the tankless it was summer. It was more than adequate to heat the water to the temperature to what I like. I live in Albany, NY. When the winter came the incoming water was much colder. It was not adequate to give me a hot bath. There was certainly an adequate amount.
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A little trick I use to get hotter water is to reduce the flow rate. Water can only heat so fast so if you can reduce the volume that is heated then the temp will go up.
--
Roger Shoaf
If you are not part of the solution, you are not dissolved in the solvent.
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Rust requires moisture and air. A empty tank is the perfect environment for fast rusting:(
Much better to leave water fl;owing with pilot off
I have some rentals and I had one water heater that I had pulled due to a bad thermocouple and had sitting for 4 years. I had a failure in another unit on a Saturday night so I swapped in the one that was sitting.
After the water heater came up to temp, I opened the kitchen tap and did not get any rusty water. It would seem to me that there is no advantage not to drain the tank for the OP. If you are worried about any residual dampness in the tank, fire it up empty until the steam blows off. the inside then will be dry as a bone.
An annual draining would also have the advantage of evacuating all the sediment while the chunks are small enough to flow out easily.
--

Roger Shoaf

About the time I had mastered getting the toothpaste back in the tube, then
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Firing up a hot water tank with no water can ruin it almost instantly espically if its electric but even gas!! BAD IDEA!
with tank hot water heater feeding tankless water out of tankless may be too hot.
If a used tank still had a perfectly intact glass lining then sitting empty might be OK, once it starts to rust then being waterless may make it worse
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Firing up a hot water tank with no water can ruin it almost instantly espically if its electric but even gas!! BAD IDEA!
I do not suggest fireing up the tank and then going to lunch, I was suggesting that if one was concerned about a little residual moisture uou could light the burner for a couple of minutes while you monitored the unit.
Kind of like setting the cast iron frying pan on the stove after you wash it.
BTW I agree that on an electric heater it would kill the element running it dry, but on the gas unit all you would do is warm up the tank a bit. On the gas you would have to get the sucker screaming hot to do any damage.
--
Roger Shoaf
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might crack the glass lining from the temp change and bring about a early failure.
Its never a good idea to heat a empty tank!
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On Tue, 6 Mar 2007 16:58:34 -0800, "Roger Shoaf"

I saw a documentry about the CSS Hunley. It was removed, and instantly started corroding faster, so they had to resubmerge under water again.
I'm guessing air has a higher concentration of O2 than water.
tom @ www.Consolidated-Loans.info
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