I wasn't doom prepping, but years ago I looked into what our small household would need in the way of backup storage capacity just for water, should our city su

I wasn't doom prepping, but years ago I looked into what our small household would need in the way of backup storage capacity just for water, should our city supply suddenly became unavailable. I don't remember the actual numbers, but it became clear that even very large tanks would not keep us going for very long at all. In an actual apocalypse, any preparations you made would probably only postpone your misery for a very short time. On the other hand, solar panels driving well pumps and similar schemes might prove me wrong. I'm curious how much extra time billionaire preppers calculate their plans will give them if and when disaster actually strikes.