How many vents can I tie together?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Alectrician, Jul 11, 2007.

  1. Alectrician

    Alectrician DIY Senior Member

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    My cabinn plumbing wall has 4 vents. Toilet (2"), shower/tub (2"), lav (2") and washer (2").

    (If it matters, the toilet will be run seperately from the gray water with diverter valves by the septic tank.)

    Can I tie all these together above the ceiling and penetrate the roof only once?
  2. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    Yes, as long as they reconnect to the main vent stack, which should be
    3" at least.
    If there's no main stack, it's not up to code, but then code varies state to state (I doubt that would though).
  3. Alectrician

    Alectrician DIY Senior Member

    Messages:
    689

    The plumbing wall is only 2x4 so I didn't think I could squeeze a 3" vent pipe in there. I was going to just vent everything individually but thought I could combine them for fewer penetrations.
  4. jimbo

    jimbo Plumber

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    True, but his first comment is that it's a cabin! Do they really have any plumbing codes anywhere where people live in "cabins"?

    So although we do traditionally try to emphasize code compliance, this is possibly a case where I would say "who cares" , and my chief concern for the owner would be "would this work OK". I suspect that if he tied all the 2's together in the attic, and went through the roof with one 3, he would not have any issues. What do you think about that approach?
  5. shacko

    shacko Master Plumber-Gas Fitter

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    vents

    Toilet 2in., lav. 1 1/2, shower/tub 1 1/2 and washer 1 1/2; tie these together in the wall, if you can and run one 2in. line to the main stack or thru the roof. It must be a minimum 2in. all the way. jimbo says "who cares", if there is no code; you will when you don't install something thats close to a reasonable practice. Luck.
    ................................................
    "If all else fails, read the directions"
  6. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    I'll go one step further...if you're not doing it "code", why not just stick a
    2"...making sure it's 20 inches or so above the roof for frost?
    Without yanking out my dfu chart, I think that'd do for a single bath/kitchen.
    Nevermind...just did...according to the chart you can run a 2" vent up to 150 feet with 7 fixture units tied in...a bathroom group is 6 alone a K Sink is 2.
    Thats my state...we're NOT UPC, but it's prolly the same.
    He might go witrh either a 3" or two seperate 2" vents.
    Of course, I have to reiterate...it isn't code.
  7. you can go through the roof with only one 3" and then split off the various 2" above the ceiling. If your wall isn't able to take a 3" it isn't a big deal IMO; you just go 2" there and that is the only place where you have less than max.

    A 3" carries more than twice 2".
    A 2" carries about twice 1.5".

    Another post mentions 1.5" vents as being sufficient minimum size for certain fixtures; it will work; it was Code everywhere decades ago, but many codes have called for 2" for years now for certain fixtures. FWIW.

    David
    edit: total distance is another factor, but I'm excluding it here since it's a cabin not a megahouse.
  8. Alectrician

    Alectrician DIY Senior Member

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    Let me rephrase. My "one bedroom 800 sq foot mountain retreat"......


    Can you define "main stack" for me?

    I'm thinking I'll tie the tub, toilet and lav together @ 2' and vent the washer seperate. Kitchen is on a different wall and seperate.
  9. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    Main stack...you're supposed to keep the vent stack above the same size as the main below all the way through the roof...which in this case is a minimum 3" for the toilet.
    I've done log cabins and I know they're no walk in the park to hide a 3" main.
    What Jimbo was implying is...well...you're not doing it to code anyway.
    So it's a judgement call on your part.
  10. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    Bottom line is it appears you can simply gather all the 2" vents to come together somewhere in a 3" vent through the roof. If that 3" vent happens to proceed down to serve the toilet directly, all the better, but it's not necessary.
  11. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    Never tried it.
    I would say this though...IF he's going to run 3" at some point and has to put a soffit in, he might just as well go it the distance, do it right instead of risking a hard lesson.
    In the same respect, common sense dictates we run a 2" wet-vent per single bath it should (in theory) work.
    This is his lucky dilemma.
    To me it seems to hinge on whether he'll do any 3" at all...if so, might as well do it right.
  12. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    Agreed. My house used to have the master bath laid out along one wall, and everything tied into a "stack" in the 6" wall behind the toilet. When we remodeled, the fixtures were scattered over 3 walls, with no opportunity for a "stack". I just left the old stack in place, and tied 3 2" in-wall vents to it in the attic. Looks like a jungle jim up there. Only problem I saw was that the 3" vent could no longer be used as a cleanout, so I added a conventional cleanout under the floor.

    Elsewhere around the house, there are 4 2" vents sticking out of the roof, venting individual fixtures, or a toilet/vanity in one case.
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