I have heard (particularly but not exclusively from my friends who grew up in Asia, where the situation may be different) that you should not drink water from a sink in the bathroom.
They believe the water from a water fountain is safe and good for drinking. However, they believe the water from the sink in the bathroom (I'm not sure why this specifically) comes from some sort of dirty water source, which is apparently still fine to wash your hands with.
It all sounds a bit strange to me; honestly, it seems more expensive to build and maintain two sets of pipes than you would save by using less purified water in some areas. But what do I know? Maybe they're right.
To be clear; this is all taking place on a college campus in Maryland, but I suspect the answer is probably the same across most of the US (possibly across the world, but I don't know).