Air Vent Valve Principle

When gas overflows from the system, it rises along the pipes and accumulates at the highest point. Air vent valves are typically installed at this highest point. When gas enters the valve chamber and accumulates at the top, the pressure increases. When the gas pressure exceeds the system pressure, the water level in the chamber drops, causing the float to descend and open the vent. After the gas is expelled, the water level rises, and the float rises, closing the vent. Similarly, when negative pressure occurs in the system, the water level in the valve chamber drops, opening the vent. Since the external atmospheric pressure is higher than the system pressure, atmospheric air enters the system through the vent, preventing the harmful effects of negative pressure. Tightening the valve cap on the valve body stops the vent. Normally, the valve cap should be in the open position. Air vent valves can also be used with isolation valves for easier maintenance.