Wet Vent basement bath within 6 ft?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by sdebord, Mar 6, 2007.

  1. sdebord

    sdebord New Member

    I have 1 bath in my home on the 2nd story, adding a 2nd bath in my basement.

    The toilet on 2nd floor is wet vented to a 4" stack (full vert venting out roof) that drops through the basement. There is a 2" vertical vent that runs alongside the stack for the sink vents. I'm adding a toilet, tub, and sink in the basement. Here is the layout from left to right in the basement floor:

    Horizonal 4" sewer line out, 4" vertical stack, then adding toilet, tub, sink, cleanout on end, still 4", all angled down towards sewer. I'm going to vent the sink out to the 2" vent line, but the tub and toilet drains are within 6 ft of the wet vent stack.

    Do I need to vent these at all since they're so close to the stack and dropping into a 4" pipe?
    Last edited: Mar 6, 2007
  2. markts30

    markts30 Commercial Plumber

    Phoenix, AZ
    Can you post a sketch and pictures...
    That will give us more info to go on...
  3. sdebord

    sdebord New Member


    Sketch has been edited a couple of times, this is the most recent
    My real question is the 6 ft rule - does it apply here, or does having multiple drains within 6 feet change anything?

    Attached Files:

    Last edited: Mar 7, 2007
  4. hj

    hj Moderator & Master Plumber Staff Member

    Cave Creek, Arizona

    That 4" is NOT a wet vent, it is a main stack. ALL the new fixtures need venting independently of it. If your drawing is an exact representation of how you intend to install the piping, then the installation is what is "all wet" not the vent.
  5. What is above these two big vertical pipes?

    trying to clear things up here....

    Your two big vertical pipes are a source of confusion.

    What is above these two big vertical pipes? I don't know how both could be drains or "wet". Are drains connected to BOTH these two vertical pipes ??? I can't figure this out from the drawing. Are you in a multistory condo building?

    A stack is a stack. Never call it wet or dry.

    A vent is either a vent as it passes through a floor and remains a vent in the next floor level, or, once it goes through the floor and comes down to another floor level, is no longer a vent (not even "wet"), but is now a stack if waste is flowing in it. AFAIK.

    However, your drawing shows TWO vertical pipes, so maybe one is a vent after all.

    All this rephrases what hj just said, in a hundred more words. :)

    New subject: the proposed 4" drain for the toilet, shower and sink. It is not allowed to oversize more than one size up, AFAIK. So after the toilet, it would be maximum 3" to the shower and 2" to the sink. It is true that an oversized pipe will give good wet venting performance; this is just information, not a recommendation to do this. Why? Because real venting is still the big question.

    Your recurring question, asking about the 6' distance, is not completely the right question to ask in this situation. Asking how to vent will focus on the right question, in my opinion.

    FWIW, this is my input; not a Master Plumber and I do agree that it is difficult to figure out what to do in your situation.

    Summary: What is above these two big vertical pipes? I don't know how both could be drains or "wet".

  6. sdebord

    sdebord New Member

    OK, so obviously I don't know my terminology, thanks for the input.

    The 2 vertical pipes are: a 4 inch stack and a 2 inch vent, both go vertical basement floor to attic. This is a house built in the '20s, so I'm sure the plumbing requirements were much less stringent at the time. All drains tie into the stack.

    All vents in the upstairs bath and kitchen tie into the 2" vent pipe. The 2" vent pipe then ties back into the 4" stack inside the attic, though, above all drains. The 4" stack is the only thing protruding through the roof so all vents are venting through the stack in the attic. I guess this is why I got confused about wet venting etc.
  7. Wow, that's a nice reaction.

    I think it's good news:
    - A vent, from the attic, to the basement.

    Since i'm not a plumber, i don't know why the vent connects like you have shown it in the diagram wherre it meets the drain in the basement. I also don't know why you have a 4" in the roof.

    The experts will tell you more.

    Look at this thread http://www.terrylove.com/forums/showthread.php?p=70741 entitled Basement DWV. The last post so far (from markts30 on 03-01-2007, 06:28 PM) shows a diagram including reventing.

    That may be the answer you need. I still don't know for sure, since I don't know enough about the two points I just mentioned about the roof and the basement drain-vent connection.

  8. sdebord

    sdebord New Member

    The diagram has been edited - a floor drain connects into 2" vent before entering 4" sewer.

    I've already knocked out a lot of my cement floor, so I'm trying to not knock out more. The 4" line is not right next to a wall, so it would be hard to get a vent out from the tub and toilet to the wall where the vent is. I won't do it if it's not going to work right, but even if it's not exactly code, neither is the rest of the plumbing.

    I guess the big question is, with a sufficient downward angle on the 4" sewer line, and the stack venting directly out the roof within 6' of my drains, plus a 2" vent near the cleanout end of the 4" sewer:
    A - aren't these pipes big enough that there will always be some airflow?
    B - will the waste flow ok in this large sized pipe?

    (I need the 4" all the way for my cleanout - roots/clay sewer down the line/industrial rooter 2x year in my area)
  9. The diagram is so clear now, nobody will ever know what I was commenting on before. :)

    You have shown a NEW vent in the diagram, if I read it correctly. Is this right? If so, why are you asking that convoluted question which includes the roof and the slope of the drain? Now don't go editing the question because then nobody will know what I'm talking about.

    Did you look at markts30 diagram? You almost have it already with that new vent you are planning on putting in.

  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    New England
    If that 2" never sees actual sewage, you can tie your other basement fixtures to it. You should not expect the main stack to provide you with a reliable vent for the basement fixtures, it should use the separate (dry) vent line. Now, if everything ties into that 2", it may be too small. Your next question might be, is the single 2" vent okay for everything in the house. To know that, you'd need to list everything that is vented by that pipe (unless I'm all wet, wouldn't be the first time!).
  11. sdebord

    sdebord New Member

    OK, I think it's getting more clear now. Thanks for all of your help. I had just vented the sink out in the first pic, but now I am venting the 4" near the cleanout, and the sink. I guess the question is whether the 2" can support all that.

    Upstairs - 1 sink, 1 toilet, 1 tub
    1st floor - kitchen sink
    basement - 1 sink, 1 toilet, 1 tub (washing machine also in adjacent room)

    Will a single 2" vent work? I sure hope so. There are only 2 of us living here so there won't be a lot all going at once, but when there are people staying with us could that cause a problem?
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