I've been having an on going problem with my window washer bottle clogging up. I've lost count the amount of times I've unblocked it. The last time I did it was about 2 weeks ago, I got that fed up with it I flushed the bottle out with boiling water and a hose pipe. Worked perfectly until today when it's clogged up again. Anyone have any tips to stop it clogging up. I use the pre-mixed fluid, maybe the concentration is too high and turns to mush.