Water Hardness - Absent going with a whole house water softener, which can get pricey, you could try a "scale inhibitor".
This one is $62
http://www.aquapurefilters.com/store...nhibitors.html
They also have one combined with a sediment filter for whole house use for $110.
http://www.aquapurefilters.com/store...58/ap141t.html
I haven't used one though.
James