What type of activation do air-admittance valves use?

Air-admittance valves operate on the principle of pressure activation. These valves are designed to allow air to enter the plumbing system when there is a negative pressure (or vacuum) in the drainage system, which helps to prevent siphoning and ensures proper drainage. The valve opens automatically in response to this pressure change, allowing air in while preventing the escape of sewer gases. This mechanism is crucial for maintaining the balance of pressure in the plumbing system without the need for external power sources or manual operation, which differentiates it from other types of activation methods. Understanding this function is vital for ensuring the proper operation of plumbing systems and preventing potential hazards associated with negative pressure situations.