WC venting alternatives

Discussion in 'Plumbing Code Questions' started by Earl001, May 9, 2011.

  1. Earl001

    Earl001 New Member

    Messages:
    15
    Location:
    El Segundo, CA
    Tried a more difficult post in the general forum with no luck (http://www.terrylove.com/forums/showthread.php?41681-DWV-layout-question-for-sunken-tub). So I’ll try here with the second part of my venting question.

    Which of the following venting layouts for a WC is permitted/recommended? Plan B requires a much longer horizontal vent so is less preferable from an installation point of view.

    Plan A
    ……………………………f…………v…………………..
    ……………………………b………..ddddz……………
    ……………………………b………..……….z…………..
    ……………………………bbhhhhhhhhyyhhhhhhhh

    Or

    Plan B
    ………………………………….….v…………………
    ……………………………f……….ddddddddddv
    ……………………………b………..………………..v
    ……………………………bbhhhhhhhhhhcc
    ………………………………………………………….c

    Where
    f = WC flange
    b = 3" 90 deg vertical to horizontal
    h = 3" horizontal run sloped at 1/4 in/ft
    d = 2" horizontal (dry) vent sloped at 1/4 in/ft
    v = 2" vent vertical to roof
    c = 3" medium 90 deg horizontal to vertical with 2â€
    y/z = 3"x3" Y fitting with 2" exit rotated ~60 deg rolled so that it is above the horizontal centerline of the drain connected to 2†45 deg bend leading to a 2" horizontal dry vent
  2. Terry

    Terry Administrator Staff Member

    Messages:
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    Location:
    Bothell, Washington
  3. Earl001

    Earl001 New Member

    Messages:
    15
    Location:
    El Segundo, CA
    Terry,

    Thank you. The tips are quite informative! However, all his photos show the vent traveling vertical or what looks like 45 deg then vertical. He does not say anything about a flat vent. Perhaps the diagram below may help explain my dilemma. Due to space limitations I must run the 3" line along the joist line to the girder. Doing so makes a vertical vent impossible. Do you think this layout will cause problems? If the Y is a problem (it's not vertical but rotated 45 deg from horizontal), I think I could fit a combination long Y to the 2" flat vent instead. In this case I'd plan to rotate it from horizontal so it is as vertical as possible.

    Attached Files:

  4. Terry

    Terry Administrator Staff Member

    Messages:
    15,016
    Location:
    Bothell, Washington
    We are allowed to do what your last post shows.
    Wye turned above the flow line of the pipe, using waste fittings below the flood level of the fixture.
  5. Earl001

    Earl001 New Member

    Messages:
    15
    Location:
    El Segundo, CA
    Great. Thank you so much Terry.

    Just so I can learn a little from this, it would be nice to know what "using waste fittings below the flood level of the fixture" means. Since I'd think the flood line for a toilet is at the rim wouldn't all fittings be below that? Or does this mean that the vent line must be dry (i.e not be a 'waste fitting' by being turned above the flow line of the pipe) since that does go above the rim.

    earl
  6. Terry

    Terry Administrator Staff Member

    Messages:
    15,016
    Location:
    Bothell, Washington
    The flood lever of a toilet is the bowl.
    Most plumbers revent at 42" which is 6" above the flood level of the highest fixture, the kitchen sink.
  7. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
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    Location:
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    The reason the vent cannot be flat is that one day the line will back up and plug the vent. Since it is meant to be a dry vent, nothing will ever wash the vent clean after this happens.

    Even a horizontal vent positioned properly above the flood rim must be pitched to allow any liquids (condensation, rainwater, etc) to flow to the drain.
  8. Earl001

    Earl001 New Member

    Messages:
    15
    Location:
    El Segundo, CA
    Yes, all my horizontal vents are sloped so no water will collect. What I will do is add a cleanout to the horizontal vent line just in case it does clog. However, even if it were clogged, isn’t there a ‘trap primer’ on the toilet fill valve that will keep the trap filled and the gases out? ... I must say I’m finding the intricacies of all this very interesting. Kind of like a three dimensional jigsaw puzzle with all sorts of rules. Another helpful fact could be that on the other side of the girder, perhaps 7-8 feet from the toilet, there is a 1.5” long wye fitting that wet vents the sinks to the 3” main line. Though that may be too far to be of any help, particularly with the drop at the girder.

    I've seen other posts indicating a flat vent below the flood line (which is what I now understand I've suggested) is not ideal (and apparently not allowed in some areas) but I don’t see any other options. I'm at least relieved that there are good plumbers who still use the method and believe it is OK.
    Last edited: May 11, 2011
  9. cacher_chick

    cacher_chick Test, Don't Guess!

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    I would challenge you to find any code that allows a flat vent below the flood rim of the fixture.
  10. Terry

    Terry Administrator Staff Member

    Messages:
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    Location:
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  11. Earl001

    Earl001 New Member

    Messages:
    15
    Location:
    El Segundo, CA
    Thanks. I must have missed the flat vent reference the first time I scanned the photos. There it is on page 12: "flat vent can be used where additional vertical clearance is required". He shows both a shower and bathtub photo of a flat vent in use. The bathtub photo is hard to see but the shower photo is clear.

    This is similar to the scenario shown in my other post with the difference that Bert's photo shows what I think is a cleanout in the vent line. My vent (see below) is routed up and horizontal to the VTR. So Bert's flat vent tip also answers my other post. I just didn't know that was considered a flat vent since the long wye goes vertical. Thanks again, your site is absolutely the best!

    proposed2.jpg
    Last edited: May 11, 2011
  12. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,248
    Location:
    Land of Cheese
    I like Bert's pages and also never noticed what he calls a flat vent.

    We refer to that as a horizontal drain, and here the a vertical vent must be within 6 feet of the trap for a 1-1/2" drain.
    Last edited: May 11, 2011
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