The Perko Flush Pro Valve offers one of the easiest to use flushing systems available for inboard engines. Simply unscrew the Flush Pro cap, connect a standard garden hose, turn on the water and start your engine. The Flush Pro valve automatically pulls fresh water into the boat's cooling system - even if the boat is in the water - flushing out the entire cooling system with fresh water. When done, shut off the engine, turn off & disconnect the hose and replace the Flush Pro cap. Your engine is flushed. Flush Pro also makes winterizing easy. Simply close your seacock after the system is drained, take off the Flush Pro cap & drop the 5/8"winterizing fitting into the Flush Pro valve. Insert one end of a 5/8"tube into the fitting and the other end into your antifreeze. Start your engine & run until the proper amount of antifreeze is sucked into the engine. Remove the winterizing fitting, replace the cap on the Flush Pro valve & you're ready for below-freezing temperatures.