Abstract: A water closet tank flush valve designed to provide a full or partial emptying of the associated water tank, as desired, when the flush valve is operated. A valve stem which is raised to unseat the flush valve is fitted externally along its length with a pair of spaced external recesses. A pair of floats are mounted on individual rotatable levers, one-above-the-other on a slotted tube surrounding the valve stem, so that the upper of the stem recesses is engaged by a detent on the lever of the upper float to retain it in the partly raised position until the water level falls to a first position, after which the first float drops to release the valve stem to seat the tank valve. When the valve stem is raised to the full height, the detent of the lower float lever similarly engages the lower recess of the valve stem as long as the water level supports the lower float.