What Is an Air Admittance Valve? Your 2026 Expert Guide
An air admittance valve (AAV) is a one-way mechanical valve that lets air into a drainage system to prevent siphonage, while stopping sewer gases from escaping into the property. In UK drainage, it's used where a conventional vent through the roof would be awkward, but it doesn't automatically replace every soil vent pipe in every … Read more

