Can I vent into the main stack?

I have tried to draw my situation. I need to vent a laundry sink (which is is the basement) an I do not have the option of running a new vent to the attic. So must I use an AAV, or can I vent into the main stack even though I am downstream from a toilet? Doesn't seem like I can go in to the main post-toilet, but I wanted a knowledgeable person's answer. I appreciate any help you can offer.

Louis

I'm assuming that the 3" stack is carrying waste from another bathroom upstairs, right?

In KY, within the last few years they are now allowing what's called a "revent" which is a tee intersecting the stack that is sweeping upside down, opposite of what you would do for a vent.

This way the probability of clogging/wastewater/waste matter is not following back down the line into the vent serving the battery of fixtures.


The reason (in my opinion) they allow this now is the drastic increase of remodeling that has occured over the years where trailing a vent up through the walls of the existing home is extensive to accomplish the feat of a "code" worthy proper connection into the venting system.

This is for remodels only in most cases, no other time.

AAV's are mechanical, so they fail. Too often they are put in and forgotten. They don't, and won't ever provide the balance or equalization in a plumbing system to work effectively.

Like anything else, it needs clarification from your local plumbing inspector for the final say.

Pretty sure that a re-vent needs to connect above the highest fixture.

The vent must be attached to the stack above the flood rim of the highest fixture.

Getting the vent up there might seem unrealistic to you, but more often than not it's really not much of a problem.

Dunbar, that is extremely helpful and very logical. I appreciate the reply. I will try to get to the attic, but if I cannot, I may vent this way.

The two subsequent replies are appreciated, and make sense, but knowing about things that are feasible, although not optimal, is much more helpful.

Thanks again.

I assume this is being done without a permit or inspections, in which case you can do anything you want to regardless of whether it would be proper in your area or not. You are treading in the area between what works and what is required.