Good quality soil will allow you to use poorer quality water.
Plus your ferts will often drop the pH slightly.
Read the link in my siggy. That soil mix with the humus in it BUFFERS pH at 6.8-6.9 and you should be able to use even your crummy tap water! Without having to adjust, even!
That stuff at the grocery store is RO water. You must add CalMag Plus to it to replace valuable minerals found in tap water. Get it at the hydro shop.