Return to the Plumbing Forum | Post a Follow-Up

 o
AAV as a vent on a main waste stack

Posted by efs (My Page) on
Tue, Dec 13, 11 at 20:27

We have two waste stacks in our house.

One is used as a main stack for solid waste (serving two full baths and a powder room), while the other was used for kitchen sink and laundry sink.

During renovation they cut out the vent for the secondary stack (the one that serves kitchen and old laundry sink). I was told that the plumber plans to use AAV on the secondary stuck in lieu of the vent that is gone (both kitchen sinks that will drain to this stuck will also have AAV on them so there will be no traditional vent on any of the fixtures that will drain to that stack). Laundry sink had no individual vent (was utilizing the vent that was cut off). Is this OK? I am in CT.


Follow-Up Postings:

 o
RE: AAV as a vent on a main waste stack

  • Posted by efs (My Page) on
    Tue, Dec 13, 11 at 23:29

from CT building code:

"... 917.7 Vent required. Within each plumbing system, a minimum of one stack vent or vent stack shall extend outdoors to the open air. ..."

Do I read this correctly that when the AAV vented drains drain into my secondary stack, this stack (or at least one waste line connected to this stack) should be vented outdoors?


 o
RE: AAV as a vent on a main waste stack

You don't have a plumber. You have a cheap hack. NO, it's not OK to vent a main stack with an AAV. Never has been anywhere, so it's not like this is an unsupervised apprentice going "oops, it's OK is Yokeltown so I assumed it's OK here." type of situation. A licensed plumber would know differently. A licensed GC would know differently. BIG RED FLAGS!


 o
RE: AAV as a vent on a main waste stack

  • Posted by efs (My Page) on
    Wed, Dec 14, 11 at 11:52

thanks- I am learning it the hard way.


 o
RE: AAV as a vent on a main waste stack

The stack in question does not require any vent..This stack is serving only the kitchen and laundry, and they will both be fitted with AAV's, therefore the stack is now only a vertical portion of a vented branch and it does not require a vent.


 o
RE: AAV as a vent on a main waste stack

  • Posted by efs (My Page) on
    Wed, Dec 14, 11 at 15:28

the laundry sink does not have any vent at the moment.

The two kitchen sinks will have AAV vents.


 o
RE: AAV as a vent on a main waste stack vertical portion

  • Posted by efs (My Page) on
    Wed, Dec 14, 11 at 15:33

the two kitchen sinks are on the first floor; the stack and laundry sink are in the basement. Is this still "vertical" portion of the vented branch?


 o
RE: AAV as a vent on a main waste stack

Yes, and if the utility sink has an 1-1/2" drain and it is not more then 6ft from the trap to the stack it does not require additional venting.


 o
RE: AAV as a vent on a main waste stack

AAV's are one-way valves, and therefore do not handle positive air pressure. This is why it is best practice not to rely on AAV's, in general.

A strong argument can be made that your kitchen + laundry stack (since it's vertical) might drain poorly at times depending on the activity in the vented stack, from tubs toilets and showers. More than that I cannot say.


 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!


Return to the Plumbing Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.


Learn more about in-text links on this page here