I fill a pail full of my tap water and let it sit out a couple of days and the PH goes from 7 up to 8 or nine as the chlorine and other shit evaporayes out. I also noticed one time when I ran out of the aged water I used some right out of the tap. what happened was I adjusted the PH added nutes and watered, there was some left over so I let it sit out over night, the next day the PH had risen back up to 7.5 as the Chlorine and shit evaporated my ph down was no longer anough to keep it in the zone. So keep an eye on the PH from when it comes out of the tap and after it sits for a day or two. This may be different depending on location.
Peace
Peace