The 110mm Push-Fit Soil Vent Air Admittance Valve (Black) is a localized, one-way pressure-relief valve designed to allow air into a soil stack while preventing foul sewer gases from escaping into the building. It offers a practical alternative to penetrating the roofline with a traditional soil vent pipe.
 
When water flows down the soil stack during a flush, it creates negative air pressure (a vacuum). The valve's internal rubber diaphragm opens under this negative pressure to draw ambient air into the system, preventing the siphonage of water traps in nearby sinks, baths, and toilets. Once pressure equalizes, the valve automatically seals shut under gravity and internal system pressure to maintain a gastight barrier.
 
Featuring a socket base with an integrated rubber ring seal, it pushes directly onto the plain spigot end of a 110mm black uPVC soil pipe. It is typically installed vertically at least 200mm above the highest discharge point (such as the spillover level of the highest basin or toilet) inside roof spaces, service ducts, or boxing. Manufactured from UV-stabilized, high-impact uPVC in compliance with UK standards (BS EN 12380 / BS EN 1329-1), the black finish coordinates with black soil and vent lines while fulfilling UK Building Regulations (Approved Document H).