Franbern
Twelve years ago when I was working in the NHS organising in-house training courses, I was always amazed as to how many (and usually the lower grade workers), asked where our water fountain was. I pointed to our kitchen tap, (Staff room), telling them there was gallons and gallons of the stuff in there.
Usually, they refused, would only drink bottled water. Strange they would happily drink the tea/coffee in our staff kitchen - not sure where they thought that water came from!!
I found a full page in an Observor Colour Magazine about bottled water and its many dangers as well as cost. Turned that into a full sized poster and plastered the walls with it. Not sure if even that got the point over.
What do you mean by lower grade workers?