Just about everyone can agree water is a top priority in a disaster/SHTF scenario. That’s why it is highly recommended that you stock up on as much water as you can. Specifically, you should stock enough so that every person in your group has at least one half gallon of drinking, and one half gallon of personal hygiene water, every day for as long as you plan on surviving.
So if you have a family of four and are stockpiling for a month (thirty days) for example, you would need at least one hundred and twenty gallons of water in total.
While stockpiling water is important, it’s more so for you to have some sort of self-sustaining water source that you can turn to in the event that your stockpile runs out. After all, you never truly know how long a disaster scenario is going to last.