Dear Pallubc
The water for construction should be tested as per IS3025--1986specially in the frame work building or where RCC is to be used in construction of building. The lab test can give the treatment method and in my view it is not fullproof method use any softner on you own wish. The bore wellwater found some time salty and need treatment but you will be surprised at some places corrporation water is not 100% fit for concrete work. So for betterment the water should be tested.Read the below artical
Suspended matter: 2000 mg per liter. To get more about water read the link below.
http://www.gharexpert.com/articles/Water-1837/Water-Construction_0.aspx