Abstract: A self-contained replacement flush valve assembly has an annular valve seat member which is sealed to the original valve seat by an elastomeric sealing ring, the valve seat member being clamped in position by a toggle assembly mounted on a screw carried by a frame received in the cistern outlet tube. The frame is of H-shape and its upper limbs are pivotally connected to the valve seat member, the lower limbs having a sliding engagement with pivoted arms of the toggle assembly to resist rotation of the toggle assembly. The toggle arms are pivotally retracted during insertion of the toggle assembly and frame into the outlet tube, but fall into extended positions so that on tightening the screw the arms clamp against the lower end of the outlet tube.