One thing most of us have learned is that there is absolutely no consistency with security. I guess it comes down to the efficiency and concentration of the individual security person(s) on the day. Both my wife and I have sailed through with bottled water (having totally forgotten we had them in our bag). I have gone through 4 security systems with the same bag and exact same contents on the same day and passed through with no problem except for the 1 time. Of course this can also be due to the random checks which are automatically selected by the machines.