Here is another one from the Mi Yodeya files. This is the long version of my answer here.
QUESTION: Many offices have a water dispenser (with hot water spout) or a hot water tap next to a sink. Is this hot tap Kosher? Assume for a moment that someone uses the tap to dispense hot water into a cup of non-Kosher instant soup or non-Kosher instant hot chocolate. Does the steam from the cup make the tap non-Kosher? – Seth J
ANSWER: You may use the water from the tap.
The following is the basis for my answer: