Flood-Guard 4 In. Rubber Float Gasket Check ValveFlood Guard operates like a check valve to seal off water back up caused by overloaded sewers. Water flows normally through the drain until the sewer begins to back up. Then the Flood Guard float rises to seal off the drain opening until the water recedes. A screwdriver and a couple of minutes are all you need to install a Flood Guard. Once in place, it can prevent property damage and a very messy clean up job. Gaskets are made of molded rubber, and