Hi
Water softeners vary in price depending on size and quality. A good water softner is around £800.
The life of the filter depends on how many bathrooms you have and how often you run water. Usually needs to be changed every 6 weeks. You can still drink from the tap.
If you would like me to come over and discuss in more detail, please don't hestitate to contact me.
Many thanks
Louis
LKB Plumbing
07842 471 970
020 7801 3138
enquiries@lkbplumbing.co.uk