Mark Nailor, CPDT, a Senior Mechanical Designer with PMH Associates in Moorestown, New Jersey, is wrapping up a project in New Jersey in which the contractor installed vent piping on a floor drain associated with an emergency eyewash/safety shower. In lieu of running vent pipe up through the roof, the contractor terminated the vent pipe below an adjacent half wall and installed what Mark thought was a vacuum breaker on the end of vent pipe.
After Mark shared a photo of the installation with our experts on the ASPE Connect Open Forum, it was discovered that the vacuum breaker was actually an air-admittance valve (AAV). But what’s the difference?
Let’s hear what our experts have to say about this situation.
The Difference Between Vacuum Breakers and AAVs
AAVs are similar to vacuum breakers and act similarly, but they admit air into the vent system when air is drawn into the vent pipe under siphon conditions. They will not relieve air (and vent gases) into the room.
AAVs are generally used only where connection to the sanitary vent for the system is not accessible or there is no way to install a vent through the roof. When they are used, there must be a fully compliant sanitary vent system with a compliant area vent through the roof.
AAVs need to be accessible. If they are located in a cabinet or access panel, that panel should not have tight seals as the AAV must allow air into the vent system to prevent trap siphon.
Are AAVs Approved?
The National Standard Plumbing Code (NSPC) allows the use of AAVs in accordance with ASSE 1050 and ASSE 1050. However, AAVs are not allowed for chemical waste.
The approved use of AAVs varies widely among jurisdictions; they may be allowed by the authority having jurisdiction (AHJ) as an “alternate means of construction.” Check with the local AHJ to see if approval and/or a code modification is required. The contractor also should obtain and provide written approval from the inspector prior to installation.
The EOR (Engineer of record) who sealed the documents and holds the liability may not be willing to accept AAVs, so ensure that the contractor has not made changes to the design or altered the intent of the design by using AAVs.
To Use or Not to Use?
Opinions differ on their use. Some believe that AAVs are a nice option to have, but they should be the exception, not the rule. Others say AAVs are a handy tool that have grown in acceptance across the industry. The use of AAVs is quite popular in Europe and Asia.
However, they appear to still be a controversial mechanical device in the plumbing industry.
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