Originally Posted by
Aviatrix
You may well have got away with taking an empty water bottle, but my understanding is that this is not allowed. The rules say that you are not allowed to take liquid containers that hold more than 100 ml, regardless of whether they are full or not. An empty water bottle is the same as one that is half full.
Do you have a source for this? Many times when I have passed through security in the US, UK and elsewhere, the security personnel specifically asked people to finish the contents of their water bottles etc so that the empty bottles could be brought through. The rules at
http://www.tsa.gov/311/index.shtm are not clear either way, but I would be surprised if TSA employees were giving specific instructions to break the rules.