Abstract: This invention relates to a dump valve for a liquid retaining tank having an outlet with a valve seat disposed over the outlet and a valve member displaceable between an open position spaced from the valve to release the liquid from the tank and a closed position for contacting the valve seat to seal the outlet, with an actuator to move the valve member between the open and closed positions. The valve member includes spaced upper and lower plates with deformable material there between to contact the valve seat. The upper plate also including stopper pins.