Best idea - find yourself a place out in the middle of nowhere with a natural spring, stream or pond and a decent sized cistern to store water supply.
Spring is best - streams and ponds too easily contaminated. Have iodine tabs.
Trying to store water is an impossible task - have 10 or so 5 gallon empty 5 gallon containers in storage. The ability to source 50-100 gallons of water in an emergency is important. Should last a couple of people a few weeks comfortably.