A flush valve system is provided having an inlet and an outlet, and a main valve element adapted for transition between a closed position and an open position is disclosed. The flush valve further includes a control chamber in communication with the inlet, and a vent outlet in communication with the outlet. The system includes a solenoid for establishing communication between the control chamber and the vent outlet to establish a pressure differential across a portion of the main valve element. The system also includes a power supply for energizing the solenoid, a deployable actuator in communication with the power supply, and a microprocessor in electrical communication with the main valve element. The microprocessor is adapted to determine a valve opening time, calculate fluid pressure based on the valve opening time, and deliver a predetermined quantity of fluid through the valve based on fluid pressure.