Pressure relief valve:
When the pressure of main pipeline exceeds the set value (especially when the water pump suddenly opens or closes), the pressure relief valve opens rapidly to release the excess pressure and maintain the main line pressure at the normal level; when the main pipeline pressure returns to normal, the pressure relief valve is closed.

Pressure holding valve:
When the altitude difference between users is large, in order to meet the priority of water use in high altitude areas, it is necessary to install pressure holding valves in low altitude areas.