An RV water softener is used in recreational vehicles to get rid of minerals that make the water ‘hard’. Typical minerals are calcium and magnesium and they are present in the water as ions that have a positive charge. Because it has a lot of ions, this type of water behaves differently to soft water. You may notice that it cannot dissolve the detergents in soap and therefore does not lather as well. It also tends to form deposits on pipes and inside appliances which can cause blockages and stop appliances from working correctly.
There are several different techniques for removing ions from water but most use resins which trigger ion-exchange or lime softening.