Patent ID: 8266733

Claim:
A flush valve assembly, comprising, a valve body having a radiused inlet portion, an upper inlet end having an inlet opening therethrough, a lower outlet end having an outlet opening therethrough, and a wall extending between the upper inlet end and the lower outlet end and having an interior surface defining a flow path that extends generally longitudinally through the valve body from the inlet opening to the outlet opening and that has a generally circular transverse cross-section, wherein at least a portion of the wall is downwardly linearly tapered and has a decreasing valve body diameter as measured transversely across the valve body, and the tapered wall portion is below the radiused inlet portion, wherein a height measured longitudinally through the valve body is about the same as or greater than a largest diameter of the transverse cross-section of the flow path; and a flapper valve cover detachably connected to the flush valve assembly and having a transverse cross-sectional diameter sufficiently large to cover the inlet opening of the valve body, a pivot mechanism having a pivot arm capable of opening and closing the flapper valve cover by a pivot motion upon actuation, and a flapper bulb depending from a lower surface of the flapper valve cover, wherein the flapper valve cover is sufficiently buoyant so as to be capable of resisting the force of flowing water and remain open so as to allow flush water to pass through the valve body when the valve body is installed on a toilet having a flush volume of about 1.6 gallons per flush or less, before closing the valve cover.