are you asking this about the water source in your area, or the water in your tank after treatments?
Water out of the tap is soft or hard depending on which region of the country you live in. It all depends on the rocks that are present in your local "water table".
If you have hard water, you will get limescale in your kettle, on the shower wall and it will be really easy to wash soap from your hands.
In soft water areas you will not get limescale forming for a very long time, and soap/shampoo will foam up really easily and be a pain to wash out.
You could even phone up (or look on the internet) for your water provider e.g. Thames valley water (for me) and get their waterhardness readings.