... yeah, sounds kinda weird, but it also sounds like you chem-types have sussed out what seems to be the likely cause.
I use a Brita almost exclusively, and with my own (GH-labelled) Handy-Dandy Liquid Cheapie PH Test Kit, it seems like the water coming out is virtually the same as what's going in (around 7.0 here in TO).
Gonna test my raw Brita water again tonight, just to make sure I'm not on drugz. Well, other than that /one/ drug ;)