Kai, I'm on the Raleigh municipal water supply (RA~20) and I did perform the all-pils malt mash pH test to diagnose a problem I was having. Using the colorpHast strips, so the reading should be 0.3 units higher than listed. Oddly, the distilled pH was higher than the tap water pH, probably due to reading error.
Tap water:
50.0 g crushed pilsen malt
200.0 g water
pH, 10 min: 5.5
Distilled water:
49.8 g crushed pilsen malt
200.1 g water
mash temperature: 76.7 F/24.8 C
pH, 10 min: 5.3