I wonder if this was in an apartment building. We owned a condo in a 5 story (4+1) apartment building and because it was taller than the San Jose water system was built for, our building needed (electric) pumps to provide water pressure to the building (there were tanks on the roof). If we lost power, then we lost water.

Now that we have moved to a 2 floor detached home (also in San Jose) we do not have that issue, and everything is gravity fed.