Basement bathroom sink drain

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by DobsRSX, Feb 26, 2021.

  1. DobsRSX

    DobsRSX New Member

    Joined:
    Feb 25, 2021
    Location:
    Ontario, Canada
    Hey all,

    First time posting, and first time Plummer lol

    Im doing a basement bathroom install, and was wondering the correct way to do the sanitary drain pipes in my situation.

    I’ve researched enough to know which fittings to use, but not sure on how to piece it together..

    I’ve attached 2 photos, can someone suggest which way is correct? Do both ways work?

    There will be a sink on each side of the wall. Thanks in advance

    797288BA-5CBD-423B-B94F-EA182E7FE402.jpeg D4F4AAA1-556A-458C-83CF-7D833749E898.jpeg
     
  2. Terry

    Terry Administrator Staff Member

    Joined:
    Aug 17, 2004
    Occupation:
    Plumber
    Location:
    Bothell, Washington
    You're better off venting the trap arms much closer. Here these two lavs are combined with a double fixture fitting.
    You're only allowed so much change of direction after the vent.

    [​IMG]
     
    Sylvan likes this.
  3. Sponsor

    Sponsor Paid Advertisement

     
    Sylvan likes this.
  4. Paulypfunk

    Paulypfunk In the Trades

    Joined:
    Feb 26, 2010
    Location:
    Seattle
    You might need a little more homework on your venting. The first thing any sink needs cross paths with is a vent. In your diagrams you don’t show venting or you show one fixture meeting with another before they find a vent. In Terry’s photo this works with two sinks because they are both hitting a shared vent at the same time, before they run down the shared drain pipe.
     
    MASTERPLUMB777 likes this.
  5. DobsRSX

    DobsRSX New Member

    Joined:
    Feb 25, 2021
    Location:
    Ontario, Canada
    Sorry I should have been more specific..

    The vent would go as follows..

    8377986C-D0C5-4D31-8ED3-581D1704BD09.jpeg
     
  6. DobsRSX

    DobsRSX New Member

    Joined:
    Feb 25, 2021
    Location:
    Ontario, Canada
    If this method is not correct, would someone be so kind to draw me a quick diagram that's correct? Frustrated, and hoping to get this done soon. Thanks kindly
     
  7. Terry

    Terry Administrator Staff Member

    Joined:
    Aug 17, 2004
    Occupation:
    Plumber
    Location:
    Bothell, Washington
    If you run the line with 2" and vent at the furthest out lav, that would work. The vent and the trap arms can be 1.5"
    So the last lav gets a 2 x 1.5 x 1.5 combo for it's vent.
     
  8. wwhitney

    wwhitney Well-Known Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    You're going to need to check your plumbing code (Ontario-wide? Canada-wide?) to get a definitive answer. I can only comment on the US codes.

    Having the drains combine before the vent is somewhat unusual. One US code (IPC) would allow it. You'd need to comply with the trap arm length for each trap separately, measured to the common vent. The other US code (UPC) would not allow your last picture.

    More common would be to move the vent takeoff to the horizontal drain between the two stub-outs. That would be dry-venting the upstream lavatory and wet venting the downstream lavatory. Both US codes would allow that. One (IPC) would allow it all in 1-1/2" pipe. The other (UPC) would require a 2" drain starting at the vent takeoff.

    If you can afford a bit of vertical drop, you could vent each trap arm separately. E.g. using a san-tee for each sink, with a LT90 (for the upstream sink) or a wye + street 45 (for the downstream sink) immediately below the san-tee. Then the two vent takeoffs could turn horizontal or combine at a height at least 6" above the sink flood level. Separate vent takeoffs would comply with either US code. I don't see an easy way to do separate vents while keeping the drains horizontal and all the vent pipes within the framing.

    Cheers, Wayne
     
    MASTERPLUMB777 likes this.
  9. DobsRSX

    DobsRSX New Member

    Joined:
    Feb 25, 2021
    Location:
    Ontario, Canada
    Thanks for the replies

    Is this what you mean? Vent each trap arm separately?

    45B9F523-7DDC-433C-9572-69CBDE26144A.jpeg
     
  10. wwhitney

    wwhitney Well-Known Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    Yes, that's a good option, with the caveat that the vent has to be pitched to drain back to the drain.

    Cheers, Wayne
     
    MASTERPLUMB777 likes this.
  11. DobsRSX

    DobsRSX New Member

    Joined:
    Feb 25, 2021
    Location:
    Ontario, Canada
    Sounds good, thanks for the help!
     
    MASTERPLUMB777 likes this.
  12. wwhitney

    wwhitney Well-Known Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    BTW, the US codes differ on sizing for the horizontal branch drain for the two lavs (the combo on the lower left and downstream). The IPC would allow 1-1/2", while the UPC would require 2".

    Cheers, Wayne
     
  13. DobsRSX

    DobsRSX New Member

    Joined:
    Feb 25, 2021
    Location:
    Ontario, Canada
    So I finished the sanitary piping, and need some verification...

    I measured out exactly 1/4” pitch, but somehow it ended up slightly less. Not sure what happened, but I’m stressing out!

    From the stack on the left to the corner is 6.5 feet, with 1.5 inch slope over that distance... which works out to be .23” pitch lol.... its slightly flat around the corner before picking up slope again.

    Will this cause any issues, or am I stressing for nothing?

    Thanks in advance!

    D25F749B-E035-4B0C-B88B-B3BB65891A0A.jpeg
    0770C93A-FA07-4FAC-BAAC-CC97546FA78F.jpeg
     
Similar Threads: Basement bathroom
Forum Title Date
Plumbing Forum, Professional & DIY Advice Basement Bathroom plumbing and venting [Questions] Jul 10, 2021
Plumbing Forum, Professional & DIY Advice New basement bathroom & venting Jun 7, 2021
Plumbing Forum, Professional & DIY Advice Basement Bathroom DWV Layout Jun 6, 2021
Plumbing Forum, Professional & DIY Advice Basement bathroom plumbing no roof vent May 10, 2021
Plumbing Forum, Professional & DIY Advice Re rough basement bathroom with unique setup Help please Apr 23, 2021

Share This Page