In its simplest explanation, the water passes through the bed of Zeolite resin. The resin normally is coated with Sodium ions but when the water touches it, the sodium ion enters the water and a calcium ion comes out and attaches itself to the resin. When the resin has used up all the sodium ions and is full of calcium ones, then you have to regenerate. First the resin bed it backwashed to remove items that were filtered out while passing through the resin. Next salt water (brine) is flushed through the resin to get rid of the calcium ions and restore Sodium ions to the resin. Then the brine tank is refilled with water to get it ready for the next regeneration and the softener is returned to the service position. Since the number of ions in the resin is a fixed amount, the amount of calcium in the water, (the hardness), will determine how often it has to be regenerated.: How do water softners work. We haev one but I am not sure how/what it does.