Is a vent or air admittance valve required when a kitchen sink drain is connected to a four inch drain line? The builder says “no”, but I thought every fixture required some kind of vent.
You thought right! Although, an AAV would probably work here, it is usually required to have a 1.5" vent going back to the main vent stack.
That is correct.
This might help.
http://www.nachi.org/plumbingcoursereleased2008.htm
Jump to “Vent Section.” I think that it’s a good course, but I’m heavily biased.
Thanks to all for your quick replies.
The things that some builders say to justify poor workmanship never cease to amaze me.
He’s confused!! He’s heard the term “wet vent” and thinks that what is the under the sink is one…No! No! No!