Comment by JuniperMesos

Where in California? Where I am in the bay area, we have quite good tap water. San Francisco famously built the Hetch Hetchy reservoir in Yosemite national park in the early 20th century, which delivers excellent water from the granite Sierra Nevadas to supply the city and a substantial fraction of the water supply in other parts of the bay area. Hetch Hetchy water needs minimal treatment.

On the other hand, I remember being shocked as a small child visiting Disneyland by how nasty the water from the water fountains there tasted, and in general the tap water in the dryer southern part of the state isn't as good (LA also has its own famous systems for getting drinking water from parts further east).