All your water should be treated to remove chlorine/chloramine. Boiling will remove chlorine, and 1/4 campden tablet per 5 gallons will remove chloramine. A municipal water quality report will tell you which is used.
If you are worried about dissolved minerals and pH affecting the mash, then you can also treat your mash and sparge water. Don't worry about top-up water.
In all honesty, though, unless your water is really whacky, it will probably just fine for a PM, particularly if you are making an ale.