ASSE (Plumbing) 1051-2021

Individual and Branch Type Air Admittance Valves (AAVs) for Sanitary Drainage Systems are devices used in plumbing drainage systems to prevent the siphonage of water trap seals. These devices do not relieve back pressure; they only allow air to enter the system. These devices are designed to be used for individual fixtures or for a horizontal branch serving multiple fixtures. When these devices are installed in a building, there shall be at least one (1) open vent terminal to relieve positive pressure which extends to the atmosphere outside of the building serving the building drain on which these devices are installed.