The 2200 Gallons Per Hour motor is sealed off by a mechanical seal design while the 1600 Gallons Per Hour model has lipseal. The impeller is carefully designed and tested to maximize head and flow. The 4000 Gallons Per Hour features a robust motor design mechanical shaft seal high impact ABS plastic and unique threaded port design. Universal base plate and choice of two different ports makes for a simple installation. Removable check valve provided. Bilge Pump Pre-Wired With Either The Non-Clogging Electronic Switch Ultima Switch Or The Electro-Magnetic Float Switch For Automatic Operation Liquid Cooled 12-Pole Motor With Double Ball Bearings For Extended Service Life 2200 Gallons Per Hour Motor Is Sealed Off By A Mechanical Seal Design While The 1600 Gallons Per Hour Model Has Lipseal Impeller Is Carefully Designed And Tested To Maximize Head And Flow Universal Base Plate And Choice Of Two Different Ports Makes For A Simple Installation