New bathroom venting questions - w diagram

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by zx6e, Jul 11, 2014.

  1. zx6e

    zx6e New Member

    Messages:
    15
    Location:
    NH
    Hello forum!

    I have a question or a few questions about venting best explained with attached diagram.
    For a new 9' x 3.5' full bath.
    There was a 3" main drain built into this space over garage with dormer roof and that's all.

    Looking to add in a shower, sink and toilet. Planning 2" drain for shower, 4 x 3" drain for toilet, and 1.5" drain off sink.
    The room has a 4'4" knee wall that I would really like to be able to use for the main vent stack. OR I could use the left in picture shower wall. It is going to be complicated and ugly to simply go straight up vertical past the roofline from the main drain because of the roof joists. Also the bathroom walls are up and that long 9' outer wall is already sheetrocked. (Other side walls have access).

    The blue lines in diagram are option 1. The pinkish lines would be option 2.

    I was told by local licensed practicing plumber that I had a maximum 6' horizontal run from traps to vents. But I've also read if you have a 2" drain / trap that max extends to 8'. Is that correct, and can I do that? If so, the shower could I think be vented to the right pictured knee wall.

    Basically, I'd like to not run a vent on the long R to L wall, and I would like to puncture the roof only once, AND have the roof be punctured on the sloping right roofline, not the left side which takes major wind / rain exposure.

    Any suggestions greatly appreciated! The plumber wasn't being too cooperative to any concerns and was a very 'in the box' regimented we do it this way type of personality.

    Thanks!

    Attached Files:

  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,642
    Location:
    Cave Creek, Arizona
    1. You do not connect the vent to the tub that way, so the tub is not vented
    2. Your sink has an "S" trap, so it is not vented
    3. You cannot run a horizontal vent under the floor for the toilet, so it is not properly vented
    4. You can have as many elbows in a vent as you need or want.
    5. 6' or 8' depends on the local code.
    6. The vent out the roof, typically has to extend above the ridge line of the roof to avoid downdrafts
  3. zx6e

    zx6e New Member

    Messages:
    15
    Location:
    NH
    Thanks for response. Hmmm. I don't know plumbing venting much at all. Almost nothing.
    I have seen in my own home, the venting is pretty wacky and more or less something like this.
    I have one vent for the whole house, a full bath and kitchen sink and all fixtures are nowhere near 6 feet or less from the main vent. In fact that vent is located upstream from bath shower, sink, toilet and only branches in the kitchen sink from another direction. That house was built 1980 and may be not current.

    For this installation, I am really not sure what venting options I have then. The sink and drain and vent route hasn't been made yet at all, so if I can make a route that's not a S and legal that shouldn't be a major problem I think.
    I may try to submit a "birds eye" view of the setup which may make it a little clearer.
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,642
    Location:
    Cave Creek, Arizona
    A fixture can be 12" from the main vent and still not be "vented" depending on how the piping is arranged The codes in 1980 were NOT much different from the current ones when it comes to venting.
  5. Terry

    Terry Administrator Staff Member

    Messages:
    15,005
    Location:
    Bothell, Washington
    [​IMG]

    Just some examples of how I plumb.

    The drawing you posted has nothing that is correct.
    You can vent the shower with the lav. For that to happen, the vent extends through the roof at the lav location. I assume you have a wall that the lav is attached to. Why didn't you use that wall?

    You future second sink, will need a drain line added, and one more vent. That drain line can't sweep past a line before the vent. You would bring that in downstream of the vent for the shower, which looks to me like the lav location.
  6. zx6e

    zx6e New Member

    Messages:
    15
    Location:
    NH
    Hi Terry and HJ. Thank you for responses.
    The wall behind the lav is a miniature nightmare. I redrafted a version of venting here:

    I guess the idea would be if I have to do something horiz / vert vent wise right behind / next to lav I'd best run it horizontal OUTSIDE the wall itself yes, outside of wall, on the inside of the bathroom wall interior to that knee wall. I could cover over the vent tube with longer counter and shelving was planned in that corner by toilet anyway. A horizontal shelf could extend and cover it too.

    Not sure at all how to manage the shower and if I even have anything that could possibly work on this new version. When it comes to venting I'm as newb as they get. I am a DIY guy, do all my own electrical and commerical electrical for friend too. Car / moto repair, all plumbing repairs etc... So I'm handy and enjoy learning and pick things up fast, but I don't know venting lets say.

    Attached Files:

  7. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,642
    Location:
    Cave Creek, Arizona
    The lav is vented but I am not sure what you are doing with the shower. The purple line is completely wrong adn would cause sewer gas in the room. What is the blue line from the shower to the lavatory. If it is ANY KIND of pipe it is incorrect.
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,642
    Location:
    Cave Creek, Arizona
    The lav is vented but I am not sure what you are doing with the shower. The purple line is completely wrong adn would cause sewer gas in the room. What is the blue line from the shower to the lavatory. If it is ANY KIND of pipe it is incorrect.
  9. Kiton

    Kiton Member

    Messages:
    61
    Location:
    Quebec
    The vent has to connect after the P trap, hj and terry can advise on best routing pipe sizes etc
    but the connection has to be after the p trap as hj mentions, or sewer gas will enter the bathroom

    Attached Files:

    Last edited: Jul 17, 2014
  10. zx6e

    zx6e New Member

    Messages:
    15
    Location:
    NH
    Thanks HJ for response and Kiton for the photoshop efforts!! Cool.
    So, I've done another version again. I deleted the purple left vent option as it was confusing.
    I basically added a vertical vent tube after the shower P trap and think it could tie into around the lav vent area.

    If this IS getting closer to a potential plan and looking ok / better, further questions:
    - Is there a min / max height I can run horizontal vents? Is just under standard counter height or high counter height (30" - 36") going to be ok?
    - After vents travel about 5.5' up total knee wall height with ceiling rafters, can I have it terminate there about 6.5' high outside or would I need to or be better off connecting vent diagonally a bit or whole way up roof to make it end up higher? (see purple 'optional extension' on V3 diagram) I don't actually want to rise above main roof ridge unless I really should as the winds there can be fierce 2x-10x a year (wind noted on diagram now too).

    Thank you again for your help and patience with a struggling newb!

    Attached Files:

  11. zx6e

    zx6e New Member

    Messages:
    15
    Location:
    NH
    And here is another version that could tie in the additional sink that could go in one day.
    Not sure if there's any way to tie that all into one vent that goes through roof.
    My biggest concern is getting the main bath vented and drained right. The other sink is really just gravy if I can plan it in now or not. If it will upset the balance / plan in main bath I'll skip it.

    Attached Files:

  12. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,175
    Location:
    Maine
    6" above the flood level rim of the highest fixture served and the shower vent you show would need to tie in above that height too.
    Terry likes this.
  13. zx6e

    zx6e New Member

    Messages:
    15
    Location:
    NH
    Hmmm. So that kind of sounds like I would need to have all horizontal vent tubes 6" min above, say the upper rim of the lav / sink then? That could makes things tougher.
  14. Terry

    Terry Administrator Staff Member

    Messages:
    15,005
    Location:
    Bothell, Washington
    They do that because you should never have water that high. This way, your vents always work.
  15. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,642
    Location:
    Cave Creek, Arizona
    quote; 6" above the flood level rim of the highest fixture served

    The requirement is 6" above the overflow level of the highest fixture, OR 42" WHICHEVER IS HIGHER. It is written that way so that if a 36" kitchen sink, for example, was connected to it, it would still be 6" above its overflow level.
  16. zx6e

    zx6e New Member

    Messages:
    15
    Location:
    NH
    Thought I had read 42" somewhere. My headache here is back then.
    Don't really have a way to do it in mind besides an exposed 2" pipe in the room. That should look fetching.
  17. Kiton

    Kiton Member

    Messages:
    61
    Location:
    Quebec
    Again, check with the plumbers, I am just suggestion alternatives, but what if you avoid the knee wall for the vent and go something like this instead to get the height required?

    Attached Files:

  18. zx6e

    zx6e New Member

    Messages:
    15
    Location:
    NH
    Thanks for suggestion. Trying to avoid digging into the main left to right wall the sink is on.
    About the only way I can think to vent lav doing that is:
    A) have exposed 2" vent pipe inside of bathroom showing.
    B) have vent in wall but elbow it out into room up about 6 feet off the ground to get it around roof rafters.
    C) make a more complicated kitchen island style sink vent.

    I do know those are ok with code in the MA state since the house has a vented island like that in the main kitchen.
  19. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,175
    Location:
    Maine
    Next year will be 40 years of plumbing for me. 35 of those as a master. I have never once run across a job that I could not do and do properly and too code and that includes venting. I have never once had to resort to using an AAV either. There is always a way. I will admit that sometimes that way involves more work, deconstruction and reconstruction (and of course money) than originally expected but believe me, it can be done. That's why we get paid the big bucks. Another wrench in the works.....you can't island vent anything but a kitchen sink.
  20. JustAHomeOwner

    JustAHomeOwner Member

    Messages:
    41
    Location:
    NY
    Question: is it allowed if a vent extends up 6" above a sink, then turns down below the sink on its way to the vent stack?
  21. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,642
    Location:
    Cave Creek, Arizona
    Not unless you have a very lenient inspector.
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