Dishwashers need "dishwasher salt" - an obvious statement I hear you say, but it's not that obvious from my experience. Even if the house has a water softener fitted, the dishwasher still requires salt. Every dishwasher leaves the factory with the softening unit set to "soft water" setting, because there are more soft water areas than hard. In some areas such as East Anglia one needs to set the water softener to hard water setting, (consult the manual). If you have a water softener in the home, leave the dishwasher setting alone but do put salt into the chamber.