You have used dishwasher salt, ever wondered what is it ? Dishwasher salt is a particular grade of granulated , crystalline sodium chloride intended for regenerating the water softener circuit of household or industrial dishwashers . Analogous to water softener salt, dishwasher salt regenerates ion exchange resins , expelling the therein trapped calcium and magnesium ions that characterize hard water . Dishwater salt granules are larger than those of table salt . The granule size ensures that the salt dissolves slowly, and that fine particles do not block the softener unit. Dishwasher salt is unsuitable for cooking as it is not considered food grade and therefore may contain toxic elements. If a dishwasher has a built-in water softener there will be a special compartment inside the dishwasher where the salt is to be added when needed. This salt compartment is separate from the detergent compartment, and generally located at the bottom of the wash