Design Features:
Vacuum Relief/Air Inlet Valves are normally closed valves and when the System Pressure becomes Negative -IT OPENS IMMEDIATELY- allowing air into the system to prevent a vacuum forming. When system pressure returns to positive, the Vacuum Relief/Air Inlet Valve closes air tight. Standard Vacuum Relief/Air Inlet Valves are designed to open with a minimal, 1/4 PSI, pressure differential across the orifice. Higher or lower relief settings are available to suit the application. Rated 125# and 250# class.