A sensor, system, and method for determining whether sufficient water is present to safely operate a pump. The sensor includes first and second conductive fittings that are physically and electrically isolated from one another by a third non-conductive fitting. Electrodes are secured to the exteriors of the first and second fittings and are electrically connected to an electronic detection device. The electronic detection device applies a voltage across the first and second fittings and detects a current flowing between the first and second fittings. The current is correlated to the presence of water between the first and second fittings. If the detected current is below a predetermined minimum, the electronic detection device turns off the pump to prevent dry-running thereof.