Santa Clara water is very hard, I definitely notice a day difference as well. I think Milpitas gets it's water from Hetch Hetchy which is apparently very high quality.
really? huh. I have a pretty strong preference for santa clara water, but that might be me confusing it with the Milpitas smell. I mean, there are a lot of good places to eat in Milpitas, but the Milpitas smell just really puts me off.