The Rule-Mate 1100GPH Automatic Bilge Pump offers superior pumping performance. As a fully-automatic pump, it operates using an internal sensor. When the water in the bilge reaches 2" (5cm), the pump will automatically activate, pumping the water to the outside of the boat. When the water reaches 3/8" (0.9cm), the pump will turn itself off until the water level rises again. This pump also features a back-up system to prevent dry running in the event that the sensor is fouled, reverting itself to a 2.5 minute cycle mode. Product features: State-of-the-art water sensing technology No float switch required Anti-fouling impeller - provides 10% more flow Submersible Ignition protection Includes back flow preventer Air vents in the body help to prevent air locking Built-in thermal cut-off Two thirds the size of the old model Comes with 2 x straight hose outlets: 25mm (1") and 28mm (1 1/8")