> Water that's coming out of your tap is generally aiming for neutral (~7 ph).

Not really. In the US at least, there’s the “Lead And Copper Rule”, which effectively requires utilities to adjust water composition to make the water minimally corrosive to copper and to lead. This often involves delivering water at a pH higher than 7. (San Francisco, for example, has water pH near 9, although it seems to be on the high end compared to other systems.)