Went out and bought two “life straws.” We have enough food to last a month without infrastructure just by virtue of large pantries, but when the water goes out, it’s gone.
My wife laughed at me, but from my perspective, if infrastructure is down for more than a month, I’m probably toast anyway. ;)
The USGov has failed in the past at an individual response level, but they're really good at compiling resources to help you and your family be independent. In fact, in San Francisco, the Emergency Response mindset for The Big One has shifted (since loma prieta) from "the government will come help you when it happens" to "do everything you can to survive for weeks without government help, when it happens."
So in your case, do more than buy life straws - store many gallons of water somewhere in your house. This can be done really easily and cheaply - save your used water bottles if need be, or just go buy a big giant plastic drum and drop some purifying tablets in it.
Keep bleach and eyedroppers in your house for when that water runs out and you need to refill with questionable water.
https://www.ready.gov/ has shitloads of easily digestible resources to prepare.
Filtering with bacterial (or if necessary, viral) grade filters, and additional chemical treatment (chlorine or iodine) is vastly more efficient.
A backpack filter does double-duty (have a few spare filters and can treat a litre or so of water in a couple of minutes without too much effort. Larger filters can be used (foot-pumped) for larger quantities.
Keep in mind that if the water's out, power may well be too.