Spring water/drinking water could have a strange water profile, depending on the source. I'd say it's probably pretty low in all the ions, although it could have weird surpluses in some. The manufacturer can give you the water profile, if you have specific brands you like to use.
Check this out:
I used to use the 5.2 until I learned a bit more about water chemistry. Mash pH is only a small function of the water profile, and not the only reason to add brewing salts.
Since water is like 99% of beer, I develop a unique water profile for every beer I brew. My water is pretty low in carbonate, sodium and chloride. When doing dark beers before I would sometimes get an overly harsh burnt flavor, or a weird kind of sweetness, or both.
Now I add flavor ions to skew it towards the profile I want. It definitely takes a light touch. My first batch, I overdid it trying to copy Burton-on-Trent and it came out really metallic-y.
Have you ever made a cake or cookies and forgot to add salt? It tastes weird and the sweetness tastes wrong. The same thing happens with ions in beer. For sweet, malty beers, I'll add at least a small amount of salt, if nothing else.
I use Brewater 3.0 to calculate my ion additions.