" no normal person is going to stockpile dozens of gallons of water around the house + purifiers + filtration systems."
Oh Really?
So Cal. is earthquake country and nearly all its freshwater supply is brought in via pipeline or aqueduct which cross major fault lines.
What will your "normal" people do without water if/when the "Big One" hits?
They'll come looking for ours, naturally

.
The point is, you're either giving too low of an estimate and that's just bad advice, or you're giving the truth and look like a crazyman to your audience.