Hi there I have been using hot water for years with no issues but recently I seem to be cracking some panes of glass. Once I left the brush on the pane with the water running whilst I answered the phone which obviously was my own stupidity. However I have noticed 3-4 other panes all upstairs which are cracked and not sure whether I have done this or not. Starting to be a bit paranoid!! The water is no hotter than 40 degrees any thoughts ....