I can't see how pure water can do any more damage than rain to anything as rain (in most places) usualy has a tds of only approx 5ppm.
Tony
Rain doesn't get scrubbed in.
It just falls onto the window.
Ian, you're so ridiculously defensive of your magical system.
It could never do anything wrong could it? :
I'm not being defensive of my magical system as you call it, just talking sense, the water is just pure water, as for being acidic, it will absorb more carbon dioxide from the atmosphere, potentially turning it into carbonic acid, but the effect is so marginal as to be barely detectable for gods sake!
rotting teeshirts? It isn't battery acid for crying out loud, and as for it being scrubbed onto the windows and so on...well it is hardly being 'scrubbed' in is it? By saying you are 'scrubbing' it in makes it sound like you are using loads of pressure and elbow grease and I certainly don't do that!
General weathering due to the elements does way more damage to paintwork and woodwork or UPVC frames than a 30 second wash once a month. (thats all the average medium size window takes)
Wind, rain and especially sunshine does the damage.
Me defending a 'magical system'?
More like others thinking it has magical properties, so powerful in can eat through tee shirts, strip varnish from woodwork...really aggressive stuff!....I don't think so!!
It's just water with no dissolved solids in it, marginally purer than rainwater is all, and because it has no dissolved solids in it, it makes it ideal for window cleaning.
Ian