Air admittance valves everywhere

Air admittance valves everywhere

I have been running into more of these on new construction. I don’t have a problem with them in island counter sinks or hard to vent areas but are the plumbers just getting lazy now?

This one was on a tub drain. There is always a main stack but in many of the newest homes they are using studor valves on everything.


Is it less than 20" below the flood rim of the tub?

Wisconsin Plumbing code AAV Requirements.

  1. Studor air admittance valve linked to alternate system approval
    The Studor air admittance valve (AAV) and accompanying system has been approved for use in Wisconsin, effective January 1, 2001.
    Because the valve can affect sizing and installation of the venting system, S&B has reviewed the Studor valve and system using the “alternate system” review process. Before issuing an alternate system approval, for over a year three staff members representing S&B field operations, plan review, and product review perspectives reviewed information submitted by the Studor company.
    Studor AAVs are sold in two sizes: the “mini-vent” and the “maxi-vent.” The mini-vent is for 1 1/4-inch through 2-inch pipe and the maxi-vent is used on 3-inch and 4-inch vent piping.

Following are the stipulations for system installation:

  1. The AAV must be installed as required in the manufacturer’s printed instructions. If the Wisconsin Plumbing Code or the alternate system approval stipulations vary from the manufacturer’s instructions, the code and stipulations must be followed.
  2. Studor valves must be tested immediately prior to or after installation. The test required is to one inch of water column positive pressure for 5 minutes.
  3. The AAV must be installed within 15 degrees from vertical.
  4. Each plumbing system using the AAV must have one three-inch vent terminating outside the building with an open pipe. Studor recommends this vent be the most downstream vent in the system. This is only a recom-mendation, not a requirement.
  5. Frost protection is required if the AAV is installed in freezing temperatures.
  6. The AAV must be installed:
  • 4 inches above the weir of the highest trap being served;
  • No more than 20 inches below the flood level rim of any fixture served;
  • At least 6 inches above insulation materials;
  • In an accessible area;
  • In a ventilated space (at least one square inch of total opening), and;
  • Within the trap to vent distances, Comm 82.31(9).
  1. Horizontal offsets less than 36 inches above the floor are permitted except where the vent connects to another vent pipe.
  2. The AAV may serve as a vent terminal for a:
  • Branch vent;
  • Individual vent;
  • Circuit vent;
  • Common vent;
  • Combination drain and vent system;
  • Stack vent;
  • Wet vent, or;
  • Vent stack.
  1. The AAV may be located:
  • Inside a building;
  • Under an overhang of a building;
  • Less than 10 feet from an air intake;
  • Less than 5 feet from a power exhaust;
  • Less than 10 feet horizontally from and less than 2 feet above roof scuttles, doors and openable windows;
  • Less than 7 feet above a roof or the surrounding grade, but not less than 8 inches above a roof; and
  • Less than 10 feet from a lot line.
  1. If a branch drain served by an AAV connects to a drain stack below 4 branch intervals, a relief vent terminating outside the building with an open pipe must be installed between the most downstream fixture of the branch and the drain stack.
  2. A branch served by an AAV shall not connect to any horizontal drain within 20 pipe diameters downstream from the base of a 2-inch or larger stack.
  3. The AAV must not be located in:
  • An enclosed stairwell;
  • An area under positive pressure for more than 12 continuous hours;
  • An area used as a supply or return air plenum; or
  • A pit, vault or depression below the adjacent grade or floor level.
  1. The AAV may not serve as a vent terminal for:
  • Vents installed to relieve positive pressure;
  • Vents serving chemical waste systems;
  • Vents serving POWTS holding or treatment tanks;
  • A stack vent serving 2 or more branch intervals; or
  • A vent required by Comm 82.31(4)(a).
  1. Vent sizing is affected when using the AAV as a vent terminal. The mini- and maxi- vent sizing tables are shown here (PDF, 54 KB).
    For more information on installation requirements for the AAV system, contact one of the plumbing plan reviewers or plumbing consultants.
1 Like

I didn’t measure but it would be really close…

Thanks for the reference. For the majority of homes they are still using traditional vents. I haven’t seen one used on a tub drain before today.

They have to be in an accessible area so it doesn’t make much sense for the tub. Mr. home Owner would not be aware of the accessibility requirement.

Yes, I always point them out to the buyers and tell them “if you ever wonder where the smell is coming from check this thing”

That thin rubber diaphragm will deteriorate with age. I believe that is why they were banner for awhile until 2001. I guess the rubber has gotten better.

I had a list of the allowed mfgs. of AAV but can’t seem to find it.
I know there was at least one that was allowwed and was later recinded.

I don’t know whether any of the sparkies make it over here to the plumbing section, but I would love to get some feed back on the electrical bonding evident in the picture. I can’t think of any reason for it with all plastic plumbing to the unit.

It was a whirlpool tub. I called it out because it went from the motor to the pipe and then hung loose just past the picture.

Other than being loose, I don’t see an issue.

Thanks David but I believe Wisconsin only permitts specific manufacturers. Mostly Studor.

That was the issue. It was not connected to a continuous ground. Some one started right, but never connected it.

You are correct…

Air admittance valves should not serve sanitary sumps

Currently there are two manufacturers of air admittance valves that are approved for use in Wisconsin; Oatey and Studor.