Ask the guy, exactly what is it that I am doing, that could cause sealed units to blow.
I have come to the conclusion that with some windows that have been misting up for a while, when we run cold water down the outside pane, it causes the mist in between the panes to condense and run down inside of window.
Customer has not noticed the misting but sees the water now running down inside of window and thinks, window cleaner has done it.
When I used to clean windows by hand, I used to notice windows starting to mist up, and I would mention it to customer, it was amazing how many had not noticed it.
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Blessings :
Graeme