Air Admittance Valve

[Billisnice]

Anyone use an Air Admittance Valve for plumbing?

http://www.studor.com/index2.htm

[MountainDon]

There's an old topic on this HERE.

IIRC they are accepted for certain types of installations depending upon your local authority. Better check before planning on using if you are subject to codes.

[Ernest T. Bass]

We used both an Oatey Sure-Vent (I think) and a cheap valve from Menards w/ no problems so far. It's only been a couple months, though..

[Billisnice]

can you just add one under the sink in the bathroom and it will handle all the fixtures in the restroom?

[glenn kangiser]

Each fixture requires a certain minimum size vent - toilet is 2 inches IIRC.  You should have regular vents where possible - use the studers for tight spots.  If there are no normal vents the system could pressurize forcing waste where you don't want it..

[ScottA]

If you want to use one on a sink thats fine IMO so long as it's accessable. I would not use on a toilet or a clothes washer. I'd recommend at a minimum one thru the roof vent at each toilet. Some area don't allow air admittance valves to be used. Check your local code. Remember anything with moving parts is likely to fail.

[Okie_Bob]

I used Studer valves exclusively on both my house and garage apartment. The reason I did is that I have metal roofs on each and didn't want ANY penetrations. I talked to several plumbers and they all said they were great alternatives and had never experienced
any problem. To date, neither have I. Suppose it would have been a good idea to use regular vent in a couple of places but, hopefully, I won't need it.

Okie Bob

[Billisnice]

That sounds great. How many did you put in for the bathrooms?

[PA-Builder]

I used Studer valves exclusively on both my house and garage apartment. The reason I did is that I have metal roofs on each and didn't want ANY penetrations.

Air Admittance Valves (AAVs) only allow air to enter INTO the system, while the main vent stack allows air to enter or exit the system.  AAVs are fine for a sink, etc.,  if local code permits; however, you still need a main vent to the outside.  If you don't want to penetrate the roof, consider taking the pipe through a sidewall.  I did a sidewall vent, and it works fine.

[Okie_Bob]

PA-Builder, I am anxious to learn from you and need to know why you feel a stack needs both air supply and exhaust? I have an unusual system. All drains flow into an old septic tank (concrete) but, no longer any lateral lines, only one line to an open overflow tank with a pump operating on a float valve. The pump obviously pumps waste out to the road to a community sewer system.
The overflow tank is open to the atmosphere (covered except for the plastic box giving access to the pump). So the system can get air in to the bottom of traps in all lines. Then  the Studer valves are at the top of each trap, if you will. So why would I need additional air?
Okie Bob

[PA-Builder]

When a column of water is flowing in a sewer drain line, and assuming the line is full, air ahead of the water is being compressed.  If the compressed air is not released through a vent, the pressure will be released through a trap.  Not desirable ! The volume of water in the line is a key element.  Usually, a drain pipe is not completely full, so the pressure issue is minimized; however, it still exists.

[Okie_Bob]

But, in my situation, the drain dumps into the old 'open' septic tank and therefore not possible to compress any air in front of the sludge flowing into it. Wouldn't that ensure it works ok? Again, I'm trying to learn here.
Okie Bob

[PA-Builder]

Bob,
It sounds like your system is working without any vent to the outside, so I would just leave it as is.  I sure wouldn't want to punch a hole in a new steel roof unless I had to.