Dishwasher salt is a particular grade of granulated,

crystalline A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

sodium chloride intended for regenerating the

water softener Water softening is the removal of calcium, magnesium, and certain other metal cations in hard water. The resulting soft water requires less soap for the same cleaning effort, as soap is not wasted bonding with calcium ions. Soft water also exten ...

circuit of household or industrial

dishwashers A dishwasher is a machine that is used to clean dishware, cookware, and cutlery automatically. Unlike manual dishwashing, which relies heavily on physical scrubbing to remove soiling, the mechanical dishwasher cleans by spraying hot water, t ...

. Analogous to

salt, dishwasher salt regenerates ion exchange resins, expelling the therein trapped

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...

and

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

s that characterize

hard water Hard water is water that has high mineral content (in contrast with "soft water"). Hard water is formed when water percolates through deposits of limestone, chalk or gypsum, which are largely made up of calcium and magnesium carbonates, bicarbo ...

. Dishwater salt granules are larger than those of

table salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...

. The granule size ensures that the

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

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. In some countries, especially those in Europe, dishwashers include a built-in

that removes

and

ions from the water. Dishwasher salt, which is coarse-grained sodium chloride (

), is used to regenerate the resin in the built-in ion-exchange system. The coarse grains prevent it from clogging the softener unit. Unlike certain types of salt used for culinary purposes, it does not contain added anticaking agents or magnesium salts. The presence of magnesium salts will defeat the purpose of removing magnesium from the water softener. Anticaking agents may lead to clogging or may contain magnesium. Table salt may contain added iodine in the form of sodium iodide or potassium iodide. These compounds will not affect the ion-exchange system, but adding table salt to the dishwasher's water softening unit can damage it. 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 cabinet (this is below the bottom basket). On most dishwashers, an automatic sensing system will notify the user when more dishwasher salt is required. If the dishwasher has run out of the salt that regenerates the ion exchange resin that softens the water, and the water supply is "hard",

limescale Limescale is a hard, chalky deposit, consisting mainly of calcium carbonate (CaCO3). It often builds up inside kettles, boilers, and pipework, especially that for hot water. It is also often found as a similar deposit on the inner surfaces of ol ...

deposits can appear on all items, but are especially visible on glassware. Even in areas with soft water there is a need to use dishwasher salt for the machine to work. There is an option to adjust the water hardness making the machine to use less amount of salt brine for every dish cycle.

References

* Water technology Dishwashing {{inorganic-compound-stub