not everyones tap water is the same ph but with that said it is always better to get water from the outside spikets tho you will be happier( leave a jug filled outside for a day and itll evaporate most chemicals)
yes some cases ph is high but some some case its too low so always check the ph,
the reason the tap water is bad is that it not only has chemicals for consumer saftey it also has to trave thru copper, steel, plastic, even lead pipes in some cases and trace mineral end up in the water when you water with this every time itll make a plant absorb iron magnesiem and other metals making un benificial for plant needs