How can you tell you aren't leaving spots on the windows?
Windows that look perfect from the outside may be full of spots when seen from inside in the early morning sunshine. Our lounge window is a perfect example. Hydrophobic glass and sunshine at just the right angle highlight even the slightest imperfection.
My resin gets changed when the tds rises to 1ppm.
How do i know, because around 90 per cent of my client base have been with me since i began window cleaning and they would say. For instance when i first switched over and was perfecting my technique, it was based on their feedback that enabled me to do so. Hence now 2 yrs in, what you are suggesting was to happen, i would know.
Or my 10 percent of what i call newish clients that ive gained along the way or recently gained, they would be quick to complain. Especially within first couple of months or so of using me. As of yet, i havent had any.
However this does not rule out that it doesnt happen. Perhaps they simply dont care or its not enough to worry about. Which if this is the case, then it also highlights that its not enough to worry about or stress about. Unless operators thenselves are OCD on the matter