A valve device comprises a body, a rotating valve set and a safety valve set. The body comprises an inner space, a first opening and a second opening. When the rotating valve set is located in a water-providing position, the inner space, the first opening and the second opening are communicable. When water pressure is higher than a safe pressure, the safety valve set and the rotating valve set can block the first opening and the second opening that safe pressure is maintained at the second opening. When water pressure becomes normal, the safety valve set is moved to its original position. Therefore, it has a piston-typed safety valve set is highly reliable. It has a coaxial structure to reduce its volume. It has an engaging and hooking structure for precise and easy assembly. It has an opening and/or closing function for its valve body with wide range of applications.
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