Water at my current home in Oakland has excellent tap water. I think the difference is that some water in the Bay Area comes from close to pristine surface sour

Water at my current home in Oakland has excellent tap water. I think the difference is that some water in the Bay Area comes from close to pristine surface sources, and is very good, while others come from ground water. The quality of groundwater will vary a lot; from great to very bad (or event toxic if you have your own well and an underground plume of waste dumped by an old chip factory comes your way).