Abstract: A valve assembly for selectively allowing either a partial or a complete draining of a toilet flush tank. A hollow valve member having both a small vent hole and a larger opening therein is selectively pivoted in a first or or a second direction depending upon which one of two activation levers is depressed. Opening the valve by pivoting it in one direction allows trapped air to vent from within the hollow valve. Inflowing water eventually imparts a negative buoyancy to the valve assembly and allows it to settle onto the valve seat to seal the tank prior to the discharge of the entire volume of water held by the flush tank. Alternatively, opening the valve by pivoting it in the opposite direction allows substantially less air to escape by virtue of the placement of the vent hole. The valve therefore never achieves negative buoyancy and the entire tank drains before the valve can settle onto its valve seat to seal the tank.