Valve System

A valve system includes a tank, a valve member, a driving device configured to move the valve member for opening and closing the tank, and a control unit. The circuit of the control unit is programmed to move the valve member in the open direction after beginning of a process, and then reverse a direction of movement of the valve member to a standby position in a valve closed state. If the first rate of pressure change in the internal pressure of the tank since the cycle began is greater than a target rate of change, the circuit determines a waiting time such that a second rate of pressure change of the internal pressure from the start to the end of the cycle is equal to the target rate of change, and then keeps the driving device in the standby position until the determined waiting time has elapsed.