|cold water tank|
|hot water tank|
|inside hot water tank (puffer)|
The drinking water at some sinks is available as acqua diretta, literally 'direct water', direct from the cold water tank, which is unsoftened; and/or as softened or treated water which is less harsh on machines (dish washers and washing machines) and pipes: thus the water we use for drinking and cooking and watering plants is quite alkaline (full of calcium) and generally mineral-rich. We check it regularly for both bacteria and minerals through a specialised laboratory. Luckily it is very good quality water.
The softening technique used is achieved through ion-exchange resins or reverse osmosis. For a technical explanation have a look here.