Some dishwashers require the addition of salt known as "dishwasher salt." It's standard table salt that is free of iodine and is used to help soften water in dishwashers. Unlike regular salt, dishwasher salt has much larger grains. Dishwasher salt is required to activate the mechanical device responsible for releasing resin balls that do the actual softening.
Why Dishwasher Salt is Important
In addition to having larger grains than regular table salt and being free of iodine, dishwasher salt dissolves slowly, so that the softener unit located in the dishwasher doesn't become clogged.
Dishwasher salt is primarily used in dishwashers in the United Kingdom, where approximately 60 percent of homes have hard water.
Always use dishwasher salt for your dishwasher. Regular table salt, sea salt, rock salt, and detergents can actually increase water hardness. Additionally, these types of salts can damage the water softener unit, which would result in an unexpected and expensive repair bill.