treated

I have seen some say they use a PUR filter on their sink. I would imagine a Brita pitcher/filter would help in the same way, right? Should the water be treated for pH (or anything else) prior to watering or is pH something which is controlled in the plant/soil itself? Is the water treated...

Lets say 40% perlite and 60% Peat moss. Is that soil or soiless? How should it be treated? Peat moss is organic with a great ability to buffer alkalinity but it has no dirt.