The Rule-Mate fully automatic submersible bilge pumps offer a more compact size with high performance & reliability. The RULE brand builds on more than 50 years of operational experience, innovation, design excellence & application expertise to offer modern solutions to todays boat owners and boat builders. The Rule-Mate bilge pumps operate using an internal water level sensor. When the bilge water level reaches 62mm height the pump will automatically activate, removing water from the bilge. When the water level goes down to 16mm height the pump will automatically shut off until the water level rises again. Hidden air vents in the body of the pump helps prevent air locking and challenging plumbing installations. A check valve is included in the discharge nozzle to prevent water running back into the bilge.