The water here in SA is awful, also. I remember when we first bought this house (1990). There was a brand new dishwasher put in when we moved in. A few years later, it just stopped working altogether. I called a repairman, and when he removed the grate from the bottom, it was full of what could only be described as stalagtites of hard water buildup. I was horrified and immediately went out and got not only a water softener, but a full reverse osmosis system put in as well.
The water here tastes horrible, and as ObZe said, if you put tap water in a glass, there is stuff floating around in it. It also has a bad taste of chlorine.
I have become very, VERY suspicious of water from a tap. I am always so pleased when I go somewhere and the water from the tap tastes good. NYC has some of the best tasting tap water anywhere. I can hardly believe how good it is.