RV portable water softeners use resin beads to soften hard water.
Simple design and easy to use.
As water flows thru softener minerals replace the sodium on the resin beads. When beads become coated you do a regen.
Regen is accomplished by pouring a box of table salt into softener and then letting it soak in the brine for 20-30 minutes then you rinse the excess salt and the minerals that have been displaced off the resins for 15-20 minutes (small pencil size flow)then you place it back in service.
8000 grain softener will treat 800 gallons of 10ppb hard water (the harder the water the less gallons can be treated)
Today RV portable softeners come in 10,000 grain and larger sizes.
We used ours during our 7 yrs of FT traveling in areas where hard water was (NM, AZ, TX etc.)
On-The-Go, FlowPur, Water Stick are some popular brands.
They ALL use same resin concept, same table salt to regen so buy whichever unit is cheapest.