Has anyone here ever used an air admittance valve on the main vent stack. I am going to call the plumbing inspector and ask if it is acceptable, but I am interested in knowing if anyone has ever had a problem with one. My shop has a metal roof and I don’t particulary want to cut a 3″ hole in it if I can avoid it. The roof is vented with soffit vents and a continouse ridge vent, so I should have pretty good cirulation.
The other thing that comes to mind is the possibility of condensation in cold weather.
All comments welcome.
Dave
Replies
Dave, I hope this is helpful:
CABO 95
3601.1.1 Required drain and vent stack.
Buildings shall have at least one soil stack running from the building drain up through the building, with the stack vent terminating outdoors above the topmost branch interval per Section 3601.5. Additional branches may be served by air admittance valves installed in accordance with Sections 3601.4 and 3601.5.6. Valves shall be sized according to Table 3601.5.6.
3601.4 Air admittance valves.
Approved air admittance valves complying with ASSE 1051 shall be permitted for a single fixture or for multiple fixture traps. The air admittance valve shall be installed to permit free movement of air and not less than 4 inches (102 mm) above the trap arm of the fixture served and shall be accessible for periodic inspection and/or replacement. Air admittance valves shall be sized to accommodate the fixture unit load of the branch or fixture that it serves in accordance with Table 3601.5.6. Devices designed to accommodate multiple pipe size connections shall be permitted.
3601.5 Vent terminals.
Vent terminals shall comply with Sections 3601.5.1 through 3601.5.6.
3601.5.1 Location of vent terminal.
Vent terminals shall not be located beneath doors, windows or other openings nor shall a vent terminal be within 5 feet (1524 mm) horizontally of an opening to the interior unless it is at least 2 feet (610 mm) above the top of the opening.
3601.5.2 Vent extension above roofs.
Vent pipe extensions through the roof shall terminate at least 6 inches (153 mm) above the high side of the penetration. Where a roof is to be used for any purpose other than weather protection, vent extensions shall run at least 7 feet (2134 mm) above the roof.
3601.5.3 Vent extension through wall or overhang.
Vents extending through a wall or building overhang shall terminate downward.
3601.5.4 Vent pipe flashing and sealing.
Vent extensions through roofs shall be made water tight by use of flashings. Vent extensions in walls or soffits shall be made weather tight by caulking.
3601.5.5 Frost closure.
Localities having an average annual minimum design temperature 0°F. (-18°C.) (ASHRAE 97.5 percent column, winter, see Chapter 3) shall be considered subject to frost closure. Vent terminals extending to the outside in such localities shall be at least 2 inches (51 mm) in diameter. When it is found necessary to increase the size of the vent terminal extension to meet this requirement, the change in diameter shall be made inside the building at least 1 foot (305 mm) below the roof. No increase in diameter is required in localities not subject to frost closure by the above criteria.
3601.5.6 Vent terminals in attic spaces.
Vent terminals equipped with approved air admittance valves may be located in accessible attic spaces when the building drainage system connects to a vented sewer. Valves complying with ASSE 1051 shall be installed above the attic insulation and shall be sized according to Table 3601.5.6.
Thanks Bob. IRC 3114.4 allows thier use according to my Plumbing Code Check book, but I am not sure what code is used locally. I'll find out Wed. morning when I call the inspector (that is the only morning he accepts or returns calls from the county I live in).
Dave
Dave,
See P3114.7 below:
2000 IRC
SECTION P3114
AIR ADMITTANCE VALVES
P3114.1 General.Vent systems utilizing air admittance valves
shall comply with this section. Individual- and branch-type air
admittance valves shall conform to ASSE 1051. Stack type air
admittance valves shall conform to ASSE 1050.
P3114.2 Installation. The valves shall be installed in
accordance with the requirements of this section and the
manufacturer’s installation instructions. Air admittance valves
shall be installed after the DWV testing required by Section
P2503.5.1 or P2503.5.2 has been performed.
P3114.3 Where permitted. Individual vents, branch vents,
circuit vents and stack vents shall be permitted to terminate
with a connection to an air admittance valve.
P3114.4 Location. The air admittance valve shall be located a
minimum of 4 inches (102 mm) above the horizontal branch
drain or fixture drain being vented. The air admittance valve
shall be located within the maximum developed length permitted
for the vent. The air admittance valve shall be installed a
minimum of 6 inches (152 mm) above insulation materials
where installed in attics.
P3114.5 Access and ventilation. Access shall be provided to
all air admittance valves. The valve shall be located within a
ventilated space that allows air to enter the valve.
P3114.6 Size. The air admittance valve shall be rated for the
size of the vent to which the valve is connected.
P3114.7 Vent required. Within each plumbing system, a minimum of
one stack vent or vent stack shall extend outdoors to the
open air.
Bob