Abstract: An improved toilet tank flush control system provides a spring member which engages a rear surface of the flap control valve of the tank to apply a pressure to the flap tending to close it, which allows the user to control the amount of water discharged in the flushing action from a minimum up to the full quantity within the tank. Two alternative embodiments of the flush control mechanism are described herein, the first being for use with American standard type toilets in which the spring is mounted on a bracket fastened to the base of the tank and stands upwardly therefrom at an angle of the order of 45 degrees to engage a base surface of the float control of the flap valve, and the second being for use with a Crane type toilets in which the spring is mounted on the overflow duct and faces downwardly to engage an upper surface of the flap valve as it pivots upwardly.