During the inspection, you should check each rotor for proper arc adjustment, thatch build up, proper rotation, worn nozzles, and worn seals. Occasionally, you may also find cracked cases and clogged screens. Most of these are simple to detect and fix. However, it requires you to spend the time to watch each rotor operating. It's important to spend the time to make sure that each part-circle rotor moves completely through its properly adjusted arc pattern.
Children playing and vandals sometimes change the rotor's arc setting.
If the arc requires modification, readjust it according to the manufacturer's instructions. As grass grows, it develops thatch. Thatch is partially decomposed organic material between the grass blade and the soil. If the grass and thatch interferes with the water stream from the nozzle, it may need to be removed and thinned. In older systems, it may be necessary to dig up the rotor, attach a riser and physically raise the height of the rotor.