Have you not asked any of your neighbours to see if they have the same problem? That would tell you if its the supply or the actual pipes in your property, and would also give you more clout when complaining to the water company if it wasn't just you.
Drinking water is very good for you, but 4 liters a day does seem excessive. I assume you always get your drinking water from the kitchen tap, as the other taps probably run off a mouldy old tank somewhere in the building.
Drinking water is very good for you, but 4 liters a day does seem excessive. I assume you always get your drinking water from the kitchen tap, as the other taps probably run off a mouldy old tank somewhere in the building.