We recommend that you water 30 minutes per zone every other day preferably in the early morning hours. The cooler temperature prevents evaporation, so more of the water reaches the roots of your grass. In addition, morning watering helps to reduce the risk of disease by allowing the blades of grass to dry quickly. Watering at night is discouraged because there is no sun to dry the leaves and they can they stay wet all night long. This can eventually lead to brown patches on your lawn and make your grass more susceptible to disease.
In extreme heat you should increase the time to 45 minutes per zone every other day. However, if we have day after day of no rain and we have temperatures in the 80's and 90's, your lawn will suffer without enough water. You should increase your watering time to EVERY day for ten days or more to get things back on track.
A good way to assess your lawn is to stick a screwdriver into the ground. If it goes in with ease, you have plenty of soil moisture and you can probably cut back on the number of times you water during the week.