How much detergent should I use in my dishwasher?

The amount of detergent depends on your water hardness, measured in grains per gallon. For soft water (0-3 grains), use about 2 teaspoons per cup, while for hard water (9-12 grains), fill each cup completely. Using too little detergent can cause poor cleaning and spotting, while too much in soft water can cause permanent etching on glassware. (Page 8)