Abstract: Apparatus for selectively conserving water used in association with a commode flush tank is disclosed. The apparatus comprises a generally rectangular plate having ratchet means for wedging the plate between two opposed walls of the tank. The plate further includes a series of longitudinally disposed circular apertures for carrying an elongated stem member downwardly into the tank. The stem member, which slidably receives an elongated float, is carried by the plate so as to maintain the float disposed relative to the buoyant outlet valve of the flush tank. Whereby upon only partial emptying of the tank in response to operating the flush lever, the float contacts the buoyant valve to effect premature closure thereof. In another embodiment, the stem and float may be disposed to one side of the buoyant valve such that a transversely extending retainer clip carried by the float applies a vertical uniform pressure to the top of the buoyant valve in order to achieve premature closure.