Once your lawn has been aerated, overseeded, and fertilized, the goal is to keep the soil surface (seed) damp for about 2 weeks. Seed swells when it get wet and shrinks when it dries. Therefore, keeping the seed damp keeps it swollen and encourages it to germinate. Watering lightly and frequently during the daylight hours is the key! The dew keeps the seed from drying out at night. This is the ONLY time of year that watering during the daylight hours is a good idea. Fall afternoons can be hot and arid, so that is the most likely time for seed to dry out. Since all irrigation systems vary in pressure and amounts delivered, the following is only a guide to point you in the right direction.
Example: Set system to start about 8:00am - 9:00am. Have it put from 10-15 minutes of water down. Repeat the same cycle about 1:00pm in the afternoon. Check the lawn late one afternoon after running the system this way for two days to make sure the soil surface stays damp. Also make sure lawn is not too wet = seed floating in puddles.
Once the seed has germinated, turn water off a few days to let soil surface dry before mowing to prevent mower damage to new grass seedlings. Return to deep, infrequent night time or early am watering until irrigation system is shut down for the winter or until November.
***If you had set more than one start time during seed germination, don’t forget to remove that start time once the seed germinates.