Fully automated, it will only turn on when the water level rises. No cycling and no battery drain. Remains off until the internal float switch rises and then stays on only until the water is evacuated. Detachable strainer provides easy access to the impeller area for removal of debris. Non mercury float switch and pump in common housing. Easily installed with the pump and switch internally wired. May be connected to manual override switch if desired. Compact design, can be used in practically all bilge pumping applications. RM500, RM750 & RM1100 size 2-3/16" D x 5" W, 4 x 2-3/16" footprint oval, RM1500 & RM2000 size 4-1/4" D x 7-1/4" W, footprint 6-1/4" x 4-1/4".