Flap valves are used for end closure of outfall lines, or in manholes, to prevent entrance of backwater. They swing open under direct pressure to release the outfall fluid and close when direct pressure is relieved. The valve disc is offset from vertical to ensure positive closing.
Flap valves are used in filtration and sewage disposal plants and in various industrial installations, and are furnished bronze mounted. Flap valves are available with flanged end connections, in sizes 4" - 30".