I was under the impression that pure water is a solvent and if used on metal for instance it would rust far more quicker than rain water fall and that pure water was also corrosive.
But then i was reading a whole lot on pure water, ultra pure water and its many usages and if safe to drink etc, regardless of used resins or not.
Another i have noticed, probably due to lack of chlorine, but ive had same customers for many years, but since using wfp and bare in mind my rotation is every 4wks.....the development of algae in groves of plastic frames leading down onto frames. Also note that yes i obviusly clean frames n sills, as anyone else noted this or is it a given