Piston-type flushometer with inner cover

A flush valve including a body having an inlet and an outlet, a main seat assembly at the outlet, an outer cover attached to the body by threads, an inner cover attached to the body within the outer cover and in sealing engagement with the body to isolate the outer cover threads from contact with water, a piston movable within the body and inner cover, the piston and the inner cover defining a pressure chamber, an exterior seal carried by the piston and bearing against an inside wall of the inner cover during movement of the piston, a refill orifice in the piston connecting the pressure chamber with the body inlet, pressure in the pressure chamber maintaining the piston closed upon the main seat assembly, a relief valve in the piston for venting the pressure chamber to the outlet, and an actuator mounted in the body and selectably engageable with the relief valve to vent the pressure chamber causing the piston to move away from the main seat assembly.

A flush valve including a body having an inlet and an outlet, a main seat assembly at said outlet, the main seat assembly having a cylindrical portion which engages an inside surface of the body to center an opening of the main seat assembly, an outer cover attached to the body, an inner cover attached to the body within the outer cover, the inner cover having a plurality of exterior centering ribs on a portion thereof, which ribs engage an inside axial surface of the body to center an inside wall of the inner cover, a piston movable within the body and inner cover, the piston having a skirt engageable within the main seat assembly opening to center the piston, the piston and the inner cover defining a pressure chamber, an exterior seal carried by the piston and bearing against said inside wall of the inner cover during movement of the piston, a refill orifice in the piston connecting the pressure chamber with the body inlet, pressure in the pressure chamber maintaining the piston closed upon the main seat assembly, a relief valve in the piston for venting the pressure chamber to the outlet, and an actuator mounted in the body and selectably engageable with the relief valve to vent the pressure chamber causing the piston to move away from the main seat assembly.