In article
Jack Stein writes:

So, I'm NOT alone....although you got me by maybe 5 years. I had
thought the tanks were lined in glass, someone told me that once... Now,
I'm thinking metal rusts slower under water than just being damp? If
damp metal is in contact with air, it rusts quickly. Not much air in
water, so, leaving it in might be better than draining it every day?

Um, no. There isn't much air in water, but there is a hell of a
lot of oxygen. Water contributes to rust so well because water is
self-ionizing (something to do with the shape of the molecule). A
small fraction of the water is always free oxygen and free hydrogen.

Beyond that, I'm completely ignorant about the details of the steel
that is used for these tanks. Maybe the typical tank-steel rusts
very slowly.

http://en.wikipedia.org/wiki/Self-ionization_of_water

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|Drew Lawson | Mrs. Tweedy! |
| | The chickens are revolting! |