No Plumbing Stacks??

House was built in 1989, 3 baths, 2 kitchens, 2 laundries, I can not find any plumbing stacks/vents to the exterior. What I am missing???

Thank you, in advance for your input.

any AAV on site?


I found two, under the sinks.

You might want to check the attic, they should be above the insulation but you know how that goes, I believe even with avv installed there should be at least one stack. they may have not finished the stack.


I looked in the attic. Nothing.


Hmm you wouldn’t happen to have a Flir camera you could run hot water and see if you can find a stack running through under the insulation , I really would think there may be at least one .

You didn’t happen to see any sticking out the wall Something like a pvc vent for a furnace did you?


Locate the main waste clean-out(s).
This is a best way to determine if any mwv(ent) exists.
W.Wilson also is on the same track as I in thinking that it may be hidden
at the top plate and /or under the insulation. Also use your nose!
Good luck in finding it.

not an advocate but they are allowed by some AHJ

within each plumbing system **a minimum of one **stack vent or a vent stack shall extend outdoors to the open air

they may have gotten creative like our /builders and installed one of these

as far as the others, further investigation required to confirm

sounds like you’ve done your job well, once the write up is completed :smiley:

I doubt the toilet is on aav and it would not be functioning without a soil stack.

There’s a builder in my area that frames a dummy chase next to the chimney for the vent stack and just makes the chimney that little bit wider.

If the stack is hidden under the insulation Robert it will still work, I had one the over month or so However the insulation was dis colored so you could find it.

One word

From “Toolbase”:

AAVs are typically made from polyvinyl chloride (PVC) plastic materials with ethylene propylene diene monomer (EPDM) rubber valve diaphragms. Valves come in two sizes: one for fixture venting and a larger size for system venting. The valves fit standard diameter pipes, ranging from 1-1/4 to 4 inches. Screening protects the valves from foreign objects and vermin. ASSE (American Society of Sanitary Engineers) standards require that AAVs be tested to reliably open and close a minimum of 500,000 times, (estimated to be at least 30 years of use) with no emanation of sewer gas. Some manufacturers claim their units are tested for up to 1.5 million cycles, or at least 80 years of use. Air Admittance Valves have been effectively used in Europe for more than two decades. U.S. manufacturers offer warranties that range from 20 years to lifetime.

From another MB (2007):

*The Uniform Plumbing Code limits the use of AAV’s to a maximum of one per structure and only with the expressed written approval of the local inspecting authority. (Generally they will only approve an AAV for use as a kitchen Island vent and even then most inspectors would prefer to see an Island Loop Vent rather than an AAV). *
*The International Residential Code requires all structures to have one “Main Vent” which must run undiminished in size from the house main drain up and out through the roof. Once the main vent is created they will permit terminating a vent;

  1. in the attic space (very bad idea because it causes excess moisture to build up in the attic insulation and sewer gasses venting into the attic can infiltrate back into the living space.)
  2. Through the wall (subject to a number of limitations).
  3. May use an unlimited number of AAV’s however AAV’s should not be used where a common atmospheric vent can be achieved*)

Not a good idea.

I agree but they are promoted and allowed by code in certain cases. Somewhere I read that they are being considered as the only vents (no outdoor vents at all) as the industry promotes/lobbies for changes to bureaucrats. These folks sometimes take the easy way out and say “OK”.

I would suggest bringing a soil stack termination to the outside .
Soffit vents (if in place, may get buried ,and cause build up of gas and moisture.

Hard to imagine if it is buried and hard to find that it would be functioning as intended.

I would most certainly recommend a Plumber sign off on it.

I did.

I have run across those before in a few cases it was so bad that you could not see anything in the attic because the whole thing was black as coal from the mold like substance. They just vented into the attic.