Steam causing spots?

[Dixiecat]

Distilled water by definition is neutral - ph 7.0, neither acidic, nor basic.

During bottling and handling it can, and often does, get "contaminated" with CO2 from the air. That exposure forms a very mild carbonic acid, which is largely harmless - even to wool.

That exact same contamination occurs in mineral water, as well. So, with mineral water you get two kinds of contaminants - minerals and carbonic acid.

Rowenta recommends against distilled water, because their heating element is coated with some substance that enhances steam production. Distilled water in some way unknown to me, and also to the representative with whom I spoke, interferes with that process. Perhaps someone from Rowenta will weigh in and inform us about the chemistry involved.

Most iron manufacturers, today, state that it is unnecessary to use distilled water, but only because their irons filter the minerals out of the tap water.

I did not say distilled water was acidic but that it acts like an acid. Nature abhors a vacuum a chem prof once told my class and distilled water is such a vacuum. When in contact with metals or other materials it tends to leach out the metals or elements in an effort to balance the chem equation. This how it can 'interfere' with the coating of which you describe.

And Craigdubh, I have been at tradeshows where Rowenta reps are selling their irons and have gone through flats of bottled water. If it's safe to drink it's safe to iron with in a Rowenta at least.