IF there was a pot and everyone is throwing something in it, that is fine and I will add what I have. But I know the people around me. While they are mostly good people but none of them is even prepared with a bottle of water. So, given the situation is short term as you say, I will only announce a bottle of water available if I see someone with some medical situation. Not only that it will help ration my stash for that situation, but it will also not reveal my preparedness in the long run.

And there is the other kind of peopele. The selfish, wolverine type of people. We have two or three of those. If they are called in from neighboring buildings to join us, I better remain thristy and not take out that bottle of water from locker. One of them is so narrowly focused, he would not mind using the water to wash his smelly feet regardless of the need of older diabetic gentleman next to him. Starting a fight with this kind of guy is not a good idea in a survival situation.

The mere presense of one of these guys in the same room will start me boiling in no time. And their behaviour in no way helps the sitaution to cool down.

I guess it all depends on the folks you expect to be there when it all happens.