Help to determine which is Vent

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by donfenyk, Dec 23, 2009.

  1. donfenyk

    donfenyk DIY Junior Member

    Messages:
    10
    Location:
    Madison
    Realized that i should have posed this as a general question and not under showers and baths.

    i am currently in the process of finishing my basement- i had the rough in for the bathroom done when i built the house.

    Toilet and shower are obvious - but i have two 2" PVC pipes coming up side by side - one is the sink and the other the vent. How can i tell them apart.


    I took a flash light and shined it down each and stuck my head in the pump pit.

    PVC1 seemed to enter the main line from above about 18 inches away from the pit. (bright light shining down from above.)

    PVC2 i could see a dim glow entering the main line also about 18 inches back but coming in from the side.

    which is the vent ???
  2. krow

    krow Plumber

    Messages:
    906
    Location:
    Ontario, Canada
    Take a picture of your set up and post it
  3. donfenyk

    donfenyk DIY Junior Member

    Messages:
    10
    Location:
    Madison
    a picture is not going to show much - two 2" PVC stubs coming out of the slab
  4. RRW

    RRW New Member

    Messages:
    91
    Location:
    Illinois
    Fill sink with hot water, drain sink while running more hot into it, feel both pipes, warm one is the sink drain.
  5. donfenyk

    donfenyk DIY Junior Member

    Messages:
    10
    Location:
    Madison
    this is just a rough in - there is no sink - that is my goal to determine which of the two to hook into the vent stack and which will be used for the sink once i install it.
  6. krow

    krow Plumber

    Messages:
    906
    Location:
    Ontario, Canada
    Sticking a light down either pipe is going to show you even less than what I suggested

    If we know in what proximity to the rest of the rough in, we would be able to give a better educated guess

    The only way to be sure, if you were to place a sewer video camera through both pipes
    Last edited: Dec 23, 2009
  7. donfenyk

    donfenyk DIY Junior Member

    Messages:
    10
    Location:
    Madison
    [​IMG]


    OK here is a picture of what i was trying to describe. The one to the left seems to go straight down into the main line that enters the basin. -when i shine a light down the one on the left i can see it when i look up the 4 in line that runs into the basin.

    The one to the right - when i shine a light down i see a line that seems to enter on the side of the main line - since its entering on the side i am assuming this is the drain.


    The shower and water closet are off to the left as you look at the two 2" stubs in the wall.


    I am looking for the following:
    - how is the vent typically tied in under the slab - in one place or does it branch out to multiple places. (the shower is about 5 feet away and the water closet about 2 1/2 feet. )


    I guess worst case - if i reverse them by accident i would easily be able to swap them. The vent is directly above at the Ceiling so i can tie into either easily.
  8. donfenyk

    donfenyk DIY Junior Member

    Messages:
    10
    Location:
    Madison
    By the way - i like the Avatar that i have- but that seems to be Madison WI and not Madison NJ :)
  9. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,304
    Location:
    Cave Creek, Arizona
    pipes

    So move to Madison WI. There is no way to tell from the pipes which is which. And since I do not see any room for the toilet and lav to the left of the pipes, or room for them, that is not a help either. Run water into the toilet opening and see which one it drains into. That will be the toilet vent, and depending on what was planned for, it could also be the sink drain, and the other one for a tub/shower. No way to tell without actually seeing the job, and ideally we should have seen what the piping looked like before the concrete was poured.
  10. donfenyk

    donfenyk DIY Junior Member

    Messages:
    10
    Location:
    Madison
    the foundation steps back 4 feet so there is room to the left in the picture that you see.

    If you invent a time machine - you and i could take a trip back 6 years and take a look at what it looked like before the foundation floor was poured. But until then we will have to come up with another solution.

    Without someone giving me a suggestion i am going to take my best guess- the pipe to the left being the vent - finish up the bathroom and if there seems to be an issue - just swap the two back. Does anyone see any issue?

    No thanks on moving to Madison WI.
  11. Terry

    Terry Administrator Staff Member

    Messages:
    14,799
    Location:
    Bothell, Washington
    The sewage ejector also has a 2" vent that needs to run through the roof.

    I'm assuming that the bathroom willl be behind the wall.
    If you see a closet flange in line with a 2" pipe, that would be the toilet vent, maybe.

    You can change the avatar in your "User CP" located at the top left of the menu bar.
  12. donfenyk

    donfenyk DIY Junior Member

    Messages:
    10
    Location:
    Madison
    Ok -
    i was able to pull the insulation out of the way and look down both of the 2 inch pipes
    one enters directly into the main PVC from above ( Y connection) assuming this is the vent.

    The other takes a 90 degree turn towards the pit and enters from the side of the main PVC closer to the pit but also a Y connection.


    so it looks like a 3 (or 4") PVC running from the pit taking a turn to the left and going to the water closet. The shower Y's into the main about 3 feet from the basin, the vent Y's into the top about 1 1/2 feet from the basin. and the remaining 2" Y's into the side of the main about 1 foot from the basin.

    It seems like the run from the water closet to where the vent enters is around 4 feet - is this going to cause any issue?
  13. Terry Love

    Terry Love Plumber

    Messages:
    37
    Location:
    Bothell, WA
    UPC allows up to six feet for the vent on the toilet.
    That would be measured from the flange to the vent.

    Other codes are different.
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