<；P>；PROBLEM TO BE SOLVED: To provide a diaphragm three-way valve simple in structure and moreover compact and low in cost, and a differential pressure drainage system. <；P>；SOLUTION: The diaphragm three-way valve includes a casing 1 having strength and sealing property that can shut off from the atmosphere； a diaphragm 2 separating the casing 1 into an operating chamber 3 and a control chamber 4； and a connecting pipe 5 and an exhaust pipe 6 connected to the operating chamber 3. The operating chamber 3 is provided with an intake valve 13 opening to and shutting off from the outside, and an exhaust chamber 21 connecting the exhaust pipe 6 to the operating chamber 3. A control valve 31 is provided between a control pipe 32 led out of the control chamber 4, and a negative pressure connecting pipe 34 connected to the exhaust pipe 6. <；P>；COPYRIGHT: (C)2011,JPO&INPIT
