DIYbanter - View Single Post - Unused water heater, leave full or empty?

The Daring Dufas[_8_]

On 2/3/2013 8:44 AM, wrote:
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.......

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. ^_^

TDD