Dual Acting Continuous Air & Vacuum Relief 50 mm (2")TWSS Dual Acting Continuous Air & Vacuum Relief Valve 50 mm (2") is for bigger pipeline projects where the volume in and out is large and the pressure flow is changeable. It evacuates air during pipeline filling and enables air intake in the event of pipeline draining. Dual Acting Continuous Relief Sealing Pressure of 5 PSI Maximum Pressure of 225PSI Air Out Take Flow of 0 235 M3 H at 0 5 PSI Air Intake Flow of 235 0 M3 H at 5 0 PSI BSP Thread 50 mm