I recently upgraded our water filtration system to a 'whole RV' system, to include:
-adjustable pressure regulator
-a 1 micron sediment pre-filter
-a .5 micro carbon block filter (taste and odor, chemicals and pesticides, plus cysts (giardia and cryptosporidium))
-an RV 'On the Go' double (16000 grain) water softener.
The filters are extra large Jumbo filters for the larger canisters, which allows sufficient throughput for the whole RV as well as the on demand water heater which requires a minimum .5 gpm flow through.
We are using potassium chloride as opposed to sodium chloride, although a bit more expensive, less harmful to you and the environment.
The RV Water Filter Store ( rv water filters, rv water regulators, rv water pumps, rv water softeners, rv water hose
) is a very good reference as well as on-line vendor.