How often you should sprinkle your lawn ultimately depends on the type of grass you have, how much water your sprinkler system puts out and the weather in your region. Some lawns need about 1 to 1½” of water per week, and many people water their lawns about two to three times per week (and usually in the morning, around 10 a.m.).
After you install your sprinkler system, consider working with a landscaping professional to help you determine the best watering schedule for your lawn.