I drank it right out of the tap and didn't have any digestive or health problems. It tastes pretty good considering it's coming out of a muddy river filled with god knows what.
Most residents told me not to drink it without boiling first though, which is one of the reasons they drink so much matte.
The only supply of drinking water in the city of buenos aires is the polluted Rio de la plata. the intake pilons can be clearly seen from the Aeroparque (city) airport and very close to shore at that.
There are many factories, for example, Argentinas rusting wreck of a paper plant in Baradero that is decades old and during a boat trip this year, i could clearly see the air and water pollution coming from this decades old relic. There is pollution from factories in this country of light or no government control, but there are also towns and cities that pollute upstream.
So potable the drinking water might be, but when you are aware that it comes from the river and youre aware of what goes into the river, it makes you think twice whether you want to drink it. Have you seen the boiling heavy metal-laden river in La Boca. While it may be south americas most polluted river, its not the only one like that in argentina. Is that where you want your drinking water to come from or do you prefer a special resevoir far outside the city. Sadly, the government has never had the initiative nor foresight to provide such a resevoir.