What is the primary function of an air admittance valve (AAV)?

An air admittance valve (AAV) serves the primary function of permitting air to enter the drainage system. This is crucial for maintaining proper ventilation within the plumbing system. When waste is discharged into the drainage pipes, it creates a vacuum that can hinder the flow of wastewater. The AAV opens when negative pressure occurs, allowing air to enter the system, thereby equalizing the pressure. This facilitates the smooth flow of wastewater and helps prevent the siphoning of water from traps, which could lead to sewer gases entering the living space.

The role of an AAV is not related to allowing gases to escape from the building; its primary objective is to prevent negative pressure and facilitate air flow into the drainage system. It does not directly influence water flow rates or regulate pressure within water lines but rather focuses on maintaining the functionality and health of the drainage system by ensuring adequate ventilation.