Quick question about AAV’s

Hey all, had a quick question about Air Admittance Valves. I am taking the plumbing course and the section on AAV’s mentions there should be one on each fixture and they should be accessible . I’ve been looking at my own home during these classes, and in my home I cannot see any on any of the faucets. Am I missing something? Thanks in advance for any help you can give.

Most of your drains will be connected to the vent stack (short plumbing pipe that extends above your roof). For plumbing in kitchen islands and places where it is impossible to connect the drain to the vent stack AAV substitutes and allows pressure equalization so the drain will discharge to the sewer / septic. In some heavily snow covered countries roof vent are not practical due to snow cover. These areas have more extensive use of AAV’s. All drains are vented by one of those methods.


Thank you so much for the help. I have neither an island or much snow so it makes perfect sense why I don’t see any in my house. I really appreciate the help.

Some jurisdictions allow these devices on the DWV system. I never came across a house whether it be slab or framed on basement or crawlspace where I could not properly vent an island sink. Plumbers who don’t know how to vent an island sink and are lazy and live in a state where this is allowed will usually install them. They do not vent the fixture properly by any means. I have a pre-built house where the plumbing was performed by so-called plumbers and I have one of these on my kitchen sink. It makes a nice bubbling sound as a sink slowly slowly drains. The problem is the device needs to build up pressure before it operates so it’s already defeating the purpose of being a vent.

Exactly, Bob has your answer, Joshua.

And, welcome to our forum. There are no stupid questions.


That’s good to know about the air vents. I’m happy to be here and can already tell that there is a wealth of information available that I will surely use. Thank again to all of you for the responses and assistance.