There is no one-size-fits-all answer to this question, as the optimal setting for your water softener will depend on several factors, including the hardness of your water and the size of your family. However, as a general rule of thumb, most water softeners should be set between 20 and 40 grains per gallon. You may need to set your water softener to the higher end of this range if you have very hard water. Conversely, if you have relatively soft water, you may get by with a setting closer to 20 grains per gallon. Ultimately, the best way to determine the optimal setting for your water softener is to consult with a professional.