When your dishwasher is leaving salt residue on your dishes or in the dishwasher itself the salt residue is most commonly caused by hard water.
The salt residue or white colored residue that is left on your dishes in your dishwasher is caused by mineral deposits that occur in hard water.
The salt residue is harmless although unsightly and you usually have to rinse the salt residue off the dishes by hand which can be annoying because the dishwasher is supposed to clean the dishes.
You can install a water softener in your house to soften the water which will prevent the salt residue from building up in your dishwasher and prevent the dishes from getting salt residue on them.
The water softener will also make your other appliances last longer as well including your water heater.
Hard water is okay to consume but it can also cause issues with appliances that use the water and some people have skin issues when showering or bathing with hard water so a water softener is a good thing to have.