I add a half-cup of white vinegar to the dish washer every time I run it. This solved the problem it had with leaving lots of soap scum and hard-water mineral residues. White vinegar also seemed to clear out blocked water-jet sources (or something; I'm hazy on the details), because the dish washer did a much better job of washing away food debris after it had run with the vinegar a few times. There is no vinegar smell left after the washer runs.