When it’s time to inspect facilities, such as water tanks, or survey the topography of its properties, the Otay Water District now turns to technology it has embraced in the past year: drones. The water agency, which serves more than 225,000 customers in eastern and southern San Diego County, uses two camera-equipped drones to get a bird’s-eye view of its vast and mostly remote sites and facilities, which include 40 potable water reservoirs, more than 20 pump stations and a treatment plant.