Just to add, it is potentially quite a serious health issue.
A guy at work got pneumonia. H + S got involved via his Dr, as the suspicion was, eventually, that he wasn't using screen wash in his washer bottle.
Turns out the Dr has seen a few cases among van drivers where they had lung infections because the company vans had no screen wash. Hot day, windows open, bugs all over the screen in a low sun. Quick squirt of the washers and dirty water comes in the drivers window.
The vans where left on tick over often, boiling hot radiator, behind hot ac condenser on some models, behind a washer bottle with no screen wash. Leaves absolutely minging water in the bottle after years of no screen wash.
There was a suggestion of legionaries . But I don't think it got that far, as the water temp has to be above 68c (?) for that to occur. But brings it home.... In fact, here's a link.
http://www.theregister.co.uk/2010/06/14/pneumonia_screenwash/