How much detergent should I use depending on my water hardness?

For hard water (8 or more grains of hardness), fill one or both detergent sections to the top line. For medium water (5 to 7 grains), fill to the middle line, and for soft water (0 to 4 grains), fill to the bottom line. Using too much detergent in soft water can cause glassware to etch, while too little will result in unclean dishes. (Page 7)