City of San Diego Water Department - Landscape Watering Calculator Gear Rotor Gear rotors are a relatively new and improved type of sprinkler. They use water pressure to turn gears inside the sprinkler body, which in turn makes the nozzles rotate. Unlike impact rotors, there is almost no wasted water from splashing and overspray. Other advantages of gear rotors include a large selection of nozzles, precision adjustments, low cost, and improved uniformity which reduces overall water use. The rotors are made of plastic and cover areas from 15 to 65 feet wide, depending on the water pressure and nozzle size. Average operating pressures range from 35 to 85 p.s.i. and gear rotor systems can be up to 85% uniform.