spotting can be caused by a few different things.
1. runs from top rubber seals or a dirty wet top frame.
2.not rinsing right down to the bottom of the window.
3.wind blowing dust onto the droplets after you ve cleaned a window.
4.not using enough water to rinse the window properly.
5.runs from underneath top openers dirtying the glass below.
6.runs from inbetween 2 top openers ruining the glass below.
7.not scrubbing and rinsing enough at the top of a window(esp on the lower panes of sash windows)
8.rinsing brush on with a dirty brush and a low flow.
please feel free to add anymore lads!