My friend disapproves, but I figure the controls in the distribution of tap water are probably about as good as those in the bottling plants.

I do keep two 5 gallon containers of the bought stuff, but that is mainly me being defensive, thinking about what would happen if the mains burst or the desalination plants stopped working for whatever reason.

These get drunk gradually over the course of a month, but are then immediately replenished. I suspect you wouldn't want even the bottled water sitting around for monthe on end.