When not allowing water flow, vertical pipes that connect the dry riser system are filled with air. This air release valve drains the sprinkler system of some but not all air in order to allow proper flow. Without the air release, a vacuum would be created and it could cause damage to the system.
Standard: According to BS2874
Thread Type: Male BSP
Test Pressure: 24 bar
Size: 3/4’’ Inlet or1’’ Inlet
Note:1’’ BSP male inlet is most commonly used