Hi all,

My question is simply: Is an auxiliary vent required for a fixture if it located within 6' of the main stack?

I have heard conflicting answers from "experts" to this question so I wanted to post my question here to settle it. Some say every fixture requires a vent, and others say if it's within 6' of the stack it does not. I've tried looking at the International Plumbing Code, but I couldn't find anything giving a definitive answer either way. My Black & Decker "Plumbing" book says that a vent is not required within 6'.

In my specific case, I'm endeavoring to install a new half bathroom in my split level house. The proposed bathroom is located on the 2nd-to-lowest floor and is on concrete slab. There is a full bath directly above this where the toilet, shower, and sink drain down the main waste stack of the house to the room I want to put the new bathroom in, it then goes about 12" below the concrete slab and cuts across horizontally to where the floor drops down about 4' to the lowest level. At this level change the pipe comes through the concrete block wall, turns 90 degrees down and goes into the lowest level's concrete slab where it cuts horizontally and runs out the hous. I want my toilet to tap into the horizontal part of this main drain pipe, between the main vertical stack and where it drops down vertically again to the lowest level. This spot is exactly 2' from both vertical sections of this main waste line, downstream from the flow of the main stack. The main drain line is 4" ABS, and I want to plumb my toilet directly into it with 4" PVC.

Thank you all in advance for your insight and knowledgeable answers,

Tom (Ohio)

tom, do me a favor..
go to your local town hall and ask the plumbing inspector if " you can tie a bathroom into an existing stack that has bathroom/s above it and not vent this lower bath if you are within 6 feet of the stack?"
if the inspector has a sense of humor he/she will laugh and throw you out.
if the inspector has no sense of humor he/she will just throw you out.

I hope you have a sense of humor. the answer to your question is the bathroom group MUST be vented. just how you go about venting it will vary. my code requires it to be vented either thru the roof or tied back into a vent stack.
other codes allow the use of a mechanical (studor) vent.

"6 feet from a main stack" is NOT a viable description, because it depends on WHAT kind of "main stack" it is and how you are attaching to it. IF there are fixtures above where you want to make the connection, then you MUST install a separate vent for them, regardless of how close, or far, they are from the waste stack.