A method of sensing water within a fuel-water separator assembly disposed within a fuel system of an internal combustion engine is provided. The method includes the steps of: A) monitoring a single selectively activatable sensor within the fuel-water separator assembly to detect the presence of water; B) determining if the sensor is activated for greater than or equal to a first predetermined percentage of time, but less than or equal to a second predetermined percentage of time and providing a first level of warning if true; and C) determining if the sensor is activated for greater than the second predetermined percentage of time and providing a second level of warning if true. An apparatus configured to perform the claimed method is also disclosed.