Installed in the pipe-rise buildings, fire water supply systems and other water supply systems, water supply pipe when the pressure exceeds the set pressure relief valve, pressure relief valves automatically open fast relief to protect the safety of the pipeline, but also for holding pressure valve, the main valve upstream Paul array of water pressure. Can accurately maintain constant pressure on the security settings. Once the overpressure relief valve quickly open and timely relief. Close smooth and reliable, eliminating pressure aftermath.