Water softeners use a few different methods to operate, but essentially the equipment "exchanges" hard minerals for either sodium or potassium. According to the Water Quality Association, some equipment also may reduce levels of arsenic, nitrates and mercury.
Softeners are available in several sizes and are rated by the amount of hardness they can remove.
The downside to water softeners is the amount of sodium added to the water. That could be unsafe for some people, but typically, people like the taste of hard water much better than soft. As a result, cold water tap lines are usually purposely left unsoftened (although, not necessarily untreated).
The following products are just a few of the newest additions to the water softener market.

Water Softener With 'ESP'
The solid state Ultra computerized demand water softener from North Star Water Conditioning features its technically advanced "ESP" computer system for greater serviceability. The computer constantly checks the softener's capacity and determines when the next regeneration would occur, helping to assure an ample supply of soft water and saves money on salt and water.Solutions For Point-Of-Entry
Cuno's line of water softeners are designed to deliver soft water to equipment areas where it is fully beneficial. Partially softened water delivered to food service equipment as needed, and zero hardness water to high temperature applications. The Maximizer valve adjusts salt usage and allows the regeneration cycle to be set to match the operation's consumption.