Building off of an IRC discussion yesterday (Apologies, I forget who came up with the idea).
Every city (Or perhaps only some of them) could have a water tower nearby, somewhat isolated. On the ground is a beat-up generator that may need some repairs and gas before you can get it working. Now, if this generator is up and running, it should fill the water tower and provide running water for the adjoining town (And evac shelter!). This could last for a week, maybe only a few days.
Ah, but zombies don’t like what you’re doing, and are inclined to maul rather loud objects (Such as noisy humans). This generator will make a rather loud racket, so you need to protect it while it runs.
So set up your barricades, gather your molotovs and bear traps, cock that shotgun because things are about to get loud!