I don't know much about Bay Area ease quality but I live in tahoe and I've used tap water for formula. Do you normally drink your tap water? I would think it it tastes okay then go for it???? I've been to Sac and I wouldn't use their tap water. I'm sure it just depends on where you're at though.
Oh and last week we were notified about brain eating ameoba in our water system. So yeah, no. We don't even bathe in our water with out a really really expensive filtering system.
Some PH levels are worse in certain brands of "purified water" than your tap water. So it actually may be better depending on your area and what kind of water you use. (I'm in no way recommending it, I just think it's interesting...I would test PH levels before you gave it to baby)