Howdy Scott

I will never understand why builders feel the need to cut corners. Very good post for sure.

Have a good one

Dale

Money, Dale.

Just Money!

Primarily profit but also because consumers will only pay so much and are always looking to get things cheaper.

I find it often,  My thinking is that the builders really do not have a clue what is right or wrong.  They are depending on the plumber to install the correct device.  How much you want to bet that the plumbers put in the mechanical vents and charge for the AAV!

Scott,

Like the soda bottle analogy, I use the same when describing plumbing venting to clients. Another place you may come across these are in attics. In certain circumstances an AAV is allowed to vent into the attic.
However it is usually an air admittance valve. Good post!

Hi James and thanks!

You bring up a very good point that I left out.  You can find AAV's all over a home, the key is that they must be accessible.  So if they are sealed up in a wall, that won't cut it.  If they are in an attic, they need to be in a location that is accessible, just like any mechanical equipment in an attic.

Another thing is that you must have at least one vent stack venting to the exterior of the home, and in some areas they are not allowed at all by local codes.

Scott,

That is exactly what I was referring to. I have found these in attics as the only vent. Not allowed unless you have 3-4 inch main stack or maybe not even then if the local AHJ doesn't allow it.

Scott, good post and good information.

If you can get a vent pipe into the attic, I can't think of a reason to put an AAV on it.  Once in the attic, it is easy to continue through the roof and have a real plumbing vent.  I have  a couple of AAVs in my house because there was no way to get a vent to the attic.  I do have a couple of other real plumbing vents also. 

Scott,

Good information, we see it frequently here. I see some in attics. If it were my home, I would not want to put a hole in my roof. Just another place for water to leak in. Occasionally we get nasty weather here on the Gulf Coast. 

I have yet to find a home with poor drainage or odors due to bad / faulty venting 

Hi Jim, I had a home not long ago that I found an open vent stack in a wall.  Now, I bet you are wondering how I found it!  This was my largest home to ever inspect, it was a little over 23,000 sf!  It was a two day inspection so I had plenty of time in the home.  I set up my work area near at what was called the "Summer Kitchen".

I had been in he home for a few hours and I kept getting a whiff of sewer gas when I passed by this section of wall.  The wall had a series of light switches and a thermostat on it.  I simply removed the cover plate on the wall switch and bingo, sewer gas!  So with a little more work I unscrewed the outlet box and I could look in the wall cavity and I found it!  The vent stack from the basement bathroom terminated in the wall cavity.

All of the other times that I have found sewer gas it has been from a dry trap either a floor drain or a sink that is never used. 

Not something we see in Chicago, but I will remember the Black for mechanical and Tan for AAV statement.

Thanks for the instructional.