Are you serious, "hyper"? Buenos Aires was among the first of the world's major cities to have potable (even tasty!) tap water. There may well be tiny villages in the Argentine countryside where drinking from the tap is still questionable, but nowhere, I think, in greater Buenos Aires.
You may enjoy a tour of the "Palacio de Aguas", downtown.
I think it's personal preference....my sister in law who was born here has never drank the tap water, she won't even use it for making coffee. I do know there's a lot of chlorine in the water, just step into a hot shower and you can smell the chlorine and even just running the tap water I can smell it.
If we have run out of bottled, Eco is the best here IMO, as there is no salt in it, I have just brought a pot to boil for about 10 minutes or so, tastes okay, but I still prefer Eco.
Ahem, bottled water contains lots of interesting chemicals from the plastic if it's more than a couple of days old, one of the chemicals is suspected to slowly cause gender change, at least in snails, lobsters and the like - stay with gin-coffe, whisky-coffe and the like.