Can be set to water during ideal times to minimize evaporation. Just attach the timer to an outdoor faucet, select a run time from 1 to 360 minutes and the time of day you would like to water, and the watering takes care of itself. Watering delay (rain delay) option – postpone watering 24, 48 or 72 hours. Manual on/off button for instant watering. Built-in safeguard: valve automatically shuts when battery is low. Two "AA" batteries (not included) are required.