Here’s my honest, over-coffee advice: If you have a modern softener with a complex valve, go for evaporated salt pellets. It’s the safest bet. If your softener is old and you don’t mind a little maintenance, solar salt pellets are the best bang for your buck.
Rock salt? Only if you’re broke and ready to clean your tank every few months. Potassium chloride? Only if your doctor told you to watch your sodium.
