An impact sprinkler pivots on a bearing on top of its threaded attachment nut. It is driven in a circular motion by a spring-loaded arm pushed back by the water stream which returns to "impact" the stream. This breaks up the water stream enabling a uniform watering area around the sprinkler. Some full-circle impact heads feature a second, short range, opposing "spreader" nozzle, which fills the close range watering coverage role provided by the rapid "return cycle" on part-circle heads. The uninterrupted flow path of impact heads makes them less vulnerable to damage and clogging by dirt and sand in the water. Thus, they are suitable for systems fed by well water.