Read so many threads here and elsewhere about water and home brew.
There does seem to just be so much conjecture......
The one thing that is apparent, that it seems the brews (various) that have received the plaudits for tasting "the best", all seem to come from soft water areas.
You will easily find evidence (provable), that utility water is and generally will be "cleaner" than any so called spring water.
Of course, there is likely to be issues of taste/flavour as people are often surprised how it can change with such tiny amounts of trace minerals and that they can pick up on it.
Personally, I suspect the argument about trace mineral being necessary is likely to be complete bollocks. I use 2 energiser to 1 nutrient to provide all the nutrients and minerals needed. Plus because I experimented with hard and soft waters in respect of taste in resulting brews, I find that I can taste the harsher notes that come from water with elevated calcium and magnesium salts (local water here comes through chalk, so lots of calcium......).
I find, that too my taste its easiest just to use RO water to provide consistency.
Its fine suggesting water softeners for hard water area but thats usually gonna require salt (don't know of the chemistry of softeners but salt seems to be the usual material added to soften water). I like salt on my fries/chips and with my margaritas, not in my meads.
We are now on a water meter anyway, as the thieving b******s who now run the service wanted ways of squeezing more out of us, so I just bought a reverse osmosis filter and am currently working out a minimal rain harvest system. The RO filter should strip any airbourne pollutants out and the water while relatively small in quantity (35 gallons per day) is plenty to supply my home brew and Clares orchid watering needs......