Is this vent system ok?

Jupe Blue · 06-05-2010, 02:31 PM

I'm in the process of remodeling an unused attic space above my kitchen into a play area. The original vent for the kitchen sink vented directly into the attic (not through the roof).

Below you will find pictures of the plumbers solution for venting. I wasn't here when he did the work, but assume the he used an AAV (air admitance valve) because it was easier to install than venting through the roof.

The closest spot for a roof vent is only 2 feet from the new opening skylight. He could have run through the floor area to the other side of the space and vented there without issue.

So, it this an appropriate use of the an AAV. Is it legal in Portland, OR (my jurisdiction)? Would you do it this way? Does the vent need to be accessible for servicing? Should I make them return and vent properly through the roof?

Thanks for your thoughts.

Plumber101 · 06-05-2010, 09:02 PM

If it is possible to go throught the roof then go through the roof.

In 15 yrs of plumbing I have only used 3 AAV's and that is something I'm not proud of but using them made the termination of the vent better that what it was when I arrived. The home owner didn't have the money to go throught the roof.

Some plumbers get lazy and use them all the time legal or not I prefer to go through the roof.

It is a mechanical device and can fail

Alan · 06-06-2010, 12:07 AM

I have never installed one yet, and don't plan on it, ESPECIALLY if the situation is as simple as you're describing it.

I am a plumbing apprentice in Oregon, and while the code does not specifically allow them, it also does not specifically prohibit them.

What gets me the most is that our code requires vents to be designed to allow free flow of air throughout the system at all times, but some inspectors still allow these things to be installed. By my interpretation, that section of the code is saying that these devices don't quite make par, but overall, it's up to the inspector.

Also, keep in mind that he may or may not be comfortable installing the flashing post-shingle, so he may request that you get a roofer to come install it.

The Engineer · 06-07-2010, 09:01 AM

In my state, AAV's are not allowed to be installed, so I don't know a whole lot about them, but the only time I would consider using one, was in a side branch off the main stack, like to a single kitchen sink or something. I would definately not use it on the main stack. The main stack not only vents your household plumbing fixtures, it also vents the main underground sewer main in the street. AVV's only allow air to enter the system under negative pressure, but will not allow air to escape under positive pressure, so sewer gas can bubble out of your traps if there was a slug of water flowing down the sewer main creating a positive pressure in your house and the air had no where to go. I would definately go through the roof on the main stack.