For example, you can install an individual AAV on each fixture and a larger AAV on the stack in the attic - and, as long as there is at least one regular vent to outside air, you're done. Easy InstallationĪAVs give you a lot of venting options, though a few limitations do exist. You can probably buy one, but if you are in an area governed by codes, the inspector won't know what to make of it and won't pass it). (Studor's compact version, the Combi-Siphon Plus, is sold almost all over the world, but not in the U.S. There are specialty AAVs rated for use outdoors and in chemical environments, and even combination trap/AAV assemblies.
#Studor air admittance valve problems code#
You'll also see code organization (such as the SBCCI) approval stamps on the packaging.Īvailable in different sizes, AAVs can be used to vent an individual fixture, a complete branch, or an entire stack of vents. To distinguish between the two devices, look for the testing protocol - ANSI/ASSE 1051 or ASSE 1050, and perhaps NSF 14 - stamped on the AAV's body. Sometimes called "cheaters," these tubular, spring-loaded $5 vents are rated for only 1/2 DFU (drainage fixture unit), and are not allowed under most building codes. AAVs cost around $25 and up, depending on the size of the vent.ĭon't confuse AAVs with smaller and cheaper mechanical vents.
If you've ever tripped over a white mushroom-shaped object up in the attic, or seen a white cylindrical device under a kitchen sink, that was probably an air admittance valve. You may have seen an AAV before and not known it. While I've been installing Studor's AAVs for quite a few years without a single failure, Oatey (800/321-9532, and other manufacturers offer them as well.Īn AAV is simply a gravity-operated, one-way air valve that allows fresh air to enter a drain system without allowing sewer air out. Under the IPC, AAVs are listed for installation under Section 917 west of the Mississippi River, they're covered under Section 301.2 of the UPC. Now, AAVs are accepted by virtually all national building codes, including the SBCCI, BOCA, IRC, and IPC plumbing codes. Developed in Europe back in the '70s, the Studor Air Admittance System (Studor, 800/447-4721, was introduced in the United States in 1988.
Available in a range of sizes, AAVs can be used to vent single fixtures, branch lines, and vent stacks, but they don't eliminate the need for at least one vent to outside air.ĪAVs aren't new. These little miracle-workers almost make traditional vent lines obsolete.Īir-admittance valves can be used wherever a traditional vent would be problematic, or simply to make fixture installation easier during a remodel. But by far the simplest solution is to install an air-admittance valve, or AAV. Venting system near the fixture to compensate, as is occasionally done for a kitchen island. It's also possible to design a complicated, labor-intensive drainage/ But there are situations where it is physically impossible to install a vent line behind the trap - when a long window is located behind a kitchen sink, for example, or when the fixture is located beneath a structural beam that can't be drilled, or when the kitchen sink or vanity is located in an island.īuilding inspectors always have a solution: expose the vent line, move the sink, move the window, or change the framing. Individual vents placed within a few feet of each trap counter pressure problems by allowing outside air to enter the drain line. Air tends to follow fast-flowing water, so water rushing down a vertical drain line can siphon water out of an adjacent horizontal branch. And a drainpipe doesn't have to be totally filled with flowing water to pull traps dry. This negative pressure can create enough suction to siphon water out of a sink trap, allowing sewer gas to enter the house through the now-empty trap. When fluids flow down an undersized drain line and completely fill it, air in the drain line is shoved ahead of the water flow (assuming there are no vents), creating positive pressure in front of the water slug and negative pressure behind.
Not only can all these holes compromise the structural integrity of the framing, they can create potential fire paths.īut vents are required by code for a reason. Vent lines are also a nuisance inside the house, running horizontally and vertically through floors, walls, and ceilings, and then on into the attic, following codes - and requiring holes - all the way. Plumbers hate cutting holes in roofs for vent lines: My left ankle is mostly stainless steel from cutting one too many of them.
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