a water saving apparatus for a tank flush mechanism in which the trapped air in the flush discharge valve is vented to terminate the flush when the water level in the tank drops to a predetermined level . a pair of water level responsive actuators , set to respond at different water levels , cooperate with a normally closed vent valve coupled to the air chamber in the flush discharge valve . as the water level in the tank drops after a flush is initiated , the actuator set at the higher level in the tank will normally respond first to open the vent valve to exhaust the air from the discharge valve and terminate the flush . to provide a large volume flush , the higher level responsive actuator is rendered non - responsive by the user &# 39 ; s manipulation of the flush handle , thereby allowing the flushing action to continue until the other actuator responds to the falling water level to open the vent valve .