The Racor Filter Funnel comes complete with a built-in DuPont Teflon® PTFE (polytetrafluoroethylene) coated stainless steel screen filter. As fuel is being filtered, free water and contaminates collect on the bottom. Because water is heavier than fuel, free water will settle to the bottom.
Free water is a collection of water molecules in the bottom of fuel cans, tanks, or drums, formed when fuel is stored for even short periods of time. The free water formation is due to condensation in the air and/or separation of water molecules from fuel.