We call them vacuum breaker valves. I don't know all the rules and you
may find that they may be different in one area from another. I believe
that generally you will find that it is considered good practice to avoid
them by using a vent stack.
They are approved for use by section P3114 in the IRC. Can be used for all
venting except that a single vent stack or stack vent is required in the
system to relieve positive pressures. That being said, there are several
states where the plumbing unions is strong enough to have them banned (cuts
into a plumbers profits don't ya know.) So it's really up to the locals as
to whether that are permitted or not. (There's nothing wrong with the actual
product, been used for many, many years here in the US without problems,
just a profit issue with plumbers is all.)
The unions have nothing to do with code restictions. They may limit the
materials that they will allow their members to install (back in the 70's,
even though NoHub cast iron was code approved, the local here would only
allow the plumbers to install service weight), but, generally, they have no
control over codes.
Also, your comments "cuts into a plumbers profits don't ya know" and "just a
profit issue with plumbers is all', are rediculous statements. You're mixing
up the union (employees) with the contractors (employers).
Contractors must use whatever code approved materials and methods are
available to them in order to REDUCE the cost of jobs so that they will be
competetive. Even with today's building boom, the profits are less than they
were because the "burden" (insurance, overhead, gas prices, etc) are out of
control and whatever "profit" is left over at the end of a job gets eaten up
by the overhead.
well, I wouldn't go so far as to say they have no say. Copper drains in
commercial buildings in mass makes zero sense, but there they are, ton o
cash for the plumbers. PVC is just as chemical proof[depending on
chemicals] as copper
It was the Minnesota Pipe Trades Association who just got in banned in
Minnesota. Their argument (Minnesota Plumbing, Heating and Cooling
Contractors and the Minnesota Mechanical Contractors Association) was based
on the controversy that the use of air admittance valves to will provide a
vent terminal inside a building, which is prohibited by the Minnesota
On the other side of the argument was the Minnesota Department of Labor and
Industry Plumbing and Engineering Unit (who had been accepting the method of
venting) and Studor, Incorporated.
Of course they can fail, even vents terminating outside can fail (freeze
over, sealed by snow or birds nest, etc.) But the truth is, they have a
proven track record of not failing, and it's for this reason that they made
it into the new International Codes.
I have seen them fail. I am sure that their failure rate is higher than
conventional stack venting. As someone suggested the mineral content of the
water supply in some areas could cause a higher failure rate and those are
the areas more likely to have banned them. Like most regulations, the
reason for the regulation may not be obvious and people tend to ignore them
when they don't see the reason. That is really dumb thing to do and to
assume that there is not a good reason for a regulation.
All depends on how far above the trap the AAV is installed.
In some locations, the installer may have gotten lazy and put it too
close(ie 4 inches or less). Repeated splashing of water against the
valve leaves mineral deposits which then cause the valve to stop operating.
In new construction, take the valve up to the next floor before
installing the AAV, and we avoid the problem. 4-6 feet of air column
under the AAV and there will be NO moisture driven up to it.
AAVs are specifically allowed by IRC. They must be accessible, located
4" above fixture drain when used for individual fixtures, 6" above flood
level of highest fixture if used for a stack vent. If located in the
attic, must be at least 6" above insulation.
UPC leaves it up to the local jurisdiction.
firstname.lastname@example.org is Joshua Putnam
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