Automatic back water valve system

A back water valve system for installing in a gravity flow sewage drain line containing air, said valve system comprising a valve body defining a water passage having an inlet and an outlet connected to the drain line, a generally flat valve blade disposed between said inlet and said outlet and moveable downwardly to an open position permitting water to flow through said passage and upwardly to a closed position blocking the flow of water through said water passage, means forming an expandable fluid chamber and including an actuator moveable between a first position and a second position, said actuator connected to said valve blade for moving said valve blade from said open position upwardly to said closed position in response to movement of said actuator from said first position to said second position, and a fluid passage extending between said expandable fluid chamber and said drain line for trapping air displaced by water backing up in the drain line for increasing the fluid pressure within said chamber to move said actuator to said second position and said valve member to said closed position.

A method of blocking the back flow of sewage water in a gravity flow sewage drain line normally containing air, comprising the steps of forming a valve body defining a water passage, connecting the passage within the drain line, supporting a valve member within the valve body for movement between a retracted open position permitting water to flow through the passage and a closed position blocking the flow of water through the passage, forming an expandable fluid chamber including an actuator moveable between a first position and a second position, connecting the actuator to the valve member for moving the valve member from the open position to the closed position in response to movement of the actuator from the first position to the second position, trapping air displaced in the drain line by the backup of water, and using trapped air to increase the pressure in the expandable fluid chamber for moving the actuator to the second position and the valve member to the closed position.

A back water valve system adapted for use with a gravity flow sewage drain line containing air, said valve system comprising a valve body defining a water passage having an inlet and an outlet, a valve member disposed between said inlet and said outlet and moveable between a retracted open position permitting water to flow through said passage and a closed position blocking the flow of water through said passage, an expandable fluid chamber member including an actuator moveable between a first position and a second position, said actuator connected to said valve member for moving said valve member from said open position to said closed position in response to movement of said actuator from said first position to said second position, a trap member for trapping air displaced by water backing up in the drain line, and said trap member connected to said expandable fluid chamber member for increasing the fluid pressure within said expandable fluid chamber member and moving said actuator to said second position and said valve member to said closed position in response to an increase in pressure of trapped air.