There are a few commercially available "inline" water filters that will help with hard water such as the API tap water filter, also available are water filters from B&Q that are predominantly just a carbon filter but these too will help reduce Calcium & fluoride deposit build up. RO water available from LFS or install a unit of your own at home (costly item) and not forgetting water softening "pillows" can be bought but some say that other issues may result from using these (don't know what these issues are never looked into it)