NSF Tests Air Admittance Valves

An AVV vents a fixture trap, elminiating
the need for a traditional vent loop.

Air admittance valves (AAVs) allow air to enter the plumbing drainage system without a vent extending to the open air. They also prevent sewer gases from escaping into a building. Air admittance valves are designed to allow air movement in one direction: from the building into the DWV (drain, waste, and vent) piping system. AAVs are not intended to prevent back pressure or air pressure in the DWV system from exceeding the atmospheric pressure. 

Air admittance valves are usually tested to one of two American Society of Sanitary Engineering Standards: ASSE 1050-Air Admittance Valves for Plumbing DWV Systems, Stack Type Devices, and ASSE 1051-Air Admittance Valves for Plumbing Drainage Systems, Fixture and Branch Devices. Both standards describe AAVs as consisting of a one-way valve designed to allow air to enter the plumbing drainage system when negative pressure develops. The standards also state that the AAV device must be closed by gravity under zero differential pressure (no flow condition) and seal under conditions of positive internal pressure.

Both ASSE 1050 and ASSE 1051 contain requirements for pressure testing of the AAV device, capacity testing, and temperature range testing. The two standards differ in the application of the AAV within the DWV system.

ASSE 1050 states: "AAVs for drain, waste, and vent stacks are designed to be installed on the top of stacks with six branch intervals or less. There must be at least one vent which extends to the atmosphere outside the building serving the same drainage system- AAVs under this standard are designed to be installed at the top of the vent stack or stack vent."

ASSE 1051 has two categories of AAVs-Type A and B. "Type A is used for single fixtures at the end of a branch. Type B is used for any configuration of fixtures connected to a branch. These AAVs are designed for installation on vented branches or branches that connect to the stack within four branch intervals of the top of the stack."

NSF tests and certifies AAVs under NSF Standard 14. NSF Standard 14 provides a mechanism for the production facility inspection, quality control, performance testing (reference to ASSE Standard), materials review, and product and literature marking. The NSF Mark for such a Certified product includes the manufacturer; product name or trademark; model number or description; type of device (ASSE 1050, ASSE 1051-A or ASSE 1051-B), and the specific end use marking, NSF-dwv.