The "tap Vs spring" arguement is also a lot of bollocks.
Tap/Utility water will prove cleaner than any spring/natural/ground water pretty much all the time.
The argument about "nutrients" in water doesn't really hold up either. There is such a low level in "drinkable" waters, as to have limited effect - apart from when you're thinking of "show" meads (because you don't add anything for nutrient values so even the tiniest amount might help).
For a water to be of use (consider, say 1 gallon of distilled or reverse osmosis water, with the normal amount of nutrients i.e. FermaidK, Fermax or similar mixed in....you certainly wouldn't drink it would you), the water would have to have the nutrient value of raw sewage. Which you wouldn't drink.... or the example I've quoted in parenthesis.....
So you would probably be better placed, and presume that all the nutrients should be added via the usual methods i.e. nutrient/energiser/whatever you want to call it/boiled bread yeast/yeast hulls etc etc.
Oh and I've heard that the water in the Vegas area, is some of the hardest (high calcium and other dissolved salts) in the US. Which might explain why I've also read that most people have filters/softening/some type of treatment in their homes for the utility water, in the Vegas area - dunno if I've read correctly though......