Inlet pressure water enters the lower cavity of the pilot valve diaphragm from the guide valve when the pressure in the pipeline exceeds the set pressure of the guide valve to make its pressure increase to open the guide valve, the main valve control room outwards drain under the effect of the inlet pressure water to open the main valve, it starts to discharge pressure. When the pressure in the pipeline drops to the set pressure, the pressure in the lower cavity of the guide valve diaphragm decreases, causing the guide valve closed. This results in increased water pressure from the guide pipe to the pilot valve, then to the main
valve control room. The main valve plate closes and begins to hold pressure.