there are so many diffrent factors involve with spotting, for instance, if we are left with spots, the first thing we do is think it has to be the frames, most of the time it is, recently the council repainted over a thousand homes window frames in my area, in buetenox, best thing was i knew about it, left it for 8 weeks, as adviced by the painter, no spots now, it took about 3 months to clear more like, what i am saying is double check with any new customers of any new developments, if your water is 000 you know the problem is elswhere and not the glass