Abstract: A flapper valve assembly including an adapter member and a flapper valve member. The adapter member includes a collar portion, a pair of trunions projecting radially outwardly from diametrically opposed locations on the collar portion, and a mounting portion extending rearwardly from the collar portion and defining an elongated slot. The flapper valve member includes a sealing disc for sealing coaction with the valve seat of the outlet passage of the tank, a float bowl extending integrally and centrally downwardly from the sealing disc for positioning within the outlet passage, and a pair of arms extending rearwardly from the sealing disc and including mounting apertures sized to button over the trunions on the adapter member to mount the valve member for pivotal movement on the adapter member between opened and closed positions relative to the valve seat of the outlet passage.