It's difficult to imagine that the cold side of a distillation process (condensing steam) might introduce more iron into resulting water than a deionizing plant would. In either case, iron levels have to be orders of magnitude lower than what comes out of some taps.
Originally Posted by Michael R 1974
I've never had an XTOL failure either. Steam distilled water is sold here in grocery stores at $3 for a 2-1/2 gallon container. Compared to the cost of everything else in photography, that's noise level. I see no reason not to keep using it for mixing/diluting XTOL and other powdered developers, diluting liquid developer/fixer concentrates and mixing Photo-Flo rinse solutions. Ultra-cheap insurance, especially where film is concerned.