From Ga and everywhere west south of Missouri we have found tremendously hard water. Some places good though. Good filters will get sulfur, iron and nasties but many but maybe not most are using water softeners too.
In La our ceramic filter was turned brown and yellow and the preliminary filter was go awful.
Austin area city water is great. Feet Worth municipal water is good.
In country need filters and or water softener, in most places.
New Mexico water was better in areas we were in but much of the country is like Tx and Az.
In Az water was real bad. .5 Micron 10 in Cannister Filters and ceramic filters worked for us. Most in the Park has softeners. Around Decatur Indiana and most farming country in the Midwest, wash your coach and it will be white with minerals. Upper Midwest, Michigan the same unless they use wells and then mud or sediment along with it. Filters will get most but not dissolved calcium.
The bigger the water softener the better especially if you wash clothes in the coach. Some use potassium chloride as opposed to sodium chloride or salt.
The resin beads are the thing now.