Toilet drain pipe with a trap?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by AskingforaFriend, Apr 25, 2021.

  1. AskingforaFriend

    AskingforaFriend New Member

    Joined:
    Apr 25, 2021
    Location:
    AR
    Problem? - Second floor toilet connected to a 3” drain pipe that “might” have a trap under the slab floor...

    This question is about “adding” a toilet on the second floor to a bathroom in a building designed as a workshop/pool house . I’ll try to be short and direct to the point, I know novels aren’t preferred but this does need history.

    I’ve had a on going project since 2013. It’s a shop/pool house (built on a concrete slab) with a couple of rooms in the attic space intended for bedrooms, one room already has a bathroom. The building also has a kitchenette which will come into play in my question.

    Before starting sheetrock in the building last year I decided to add a last minute small bathroom to the other room upstairs. The new bathroom is located directly above the kitchenette sink. I utilized the same kitchenette drain pipe/vent pipe for the bathroom sink. Now I needed to plumb the toilet into waste system stack.

    Here’s where I may have a potential problem.
    The kitchenette was roughed in with a 2” sink drain and vent in the 2x6 wall. For a unknown reason, the hot/cold water lines AND a 3” drain pipe (between the water lines) were rouged in the slab coming up 10” in front of the 2x6 wall.

    The plumber that finished roughing in the building after it was framed told me the 3” pipe was of no use and asked if he should plug it. At the time I saw no use for 3” pipe thinking it was a error and agreed to plug it.

    Back to the new bathroom. As I determined the best route for the new 3” toilet drain pipe I remembered the plugged drain pipe. All I needed to do was remove the plug and route the pipe up into the 2x6 wall and then connect to the toilet drain pipe between the first and second floor. Simple solution and we moved on to the finishing stage of this long term project...

    Recently I was searching the Internet about a plumbing question when I coincidentally read a thread about a ice maker 3” floor drain with a trap.... it took a while but I literally woke up early the next day thinking about the way I connected the new toilet to the waste system...

    It’s been eight years since this project started and blueprint versions along with contractors have come and gone. I don’t know who installed the plumbing in the slab but it really doesn’t matter now.

    So... will a toilet on a second floor draining into a pipe in a concrete slab with a trap (assuming) pose a problem... ??

    I’m going to place a camera in the 3” pipe and hopefully determine if there is a trap.

    Thanks for any advice...
     
    MASTERPLUMB777 likes this.
  2. Terry

    Terry Administrator Staff Member

    Joined:
    Aug 17, 2004
    Occupation:
    Plumber
    Location:
    Bothell, Washington
    Using a downstairs vent for a sink on the floor above? That's not how we do things.

    [​IMG]
     
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  4. AskingforaFriend

    AskingforaFriend New Member

    Joined:
    Apr 25, 2021
    Location:
    AR
    A toilet drain doesn't have a trap. The trap is incorporated into the bowl.

    [​IMG]

    Water in the bowl is what prevents sewer gas from entering the home.
    All other fixtures have traps that are vented to prevent siphoning.

    The two story diagram shows how plumbing is installed with proper venting through the roof, and how it ties in below a floor. What does your plumbing look like?
    Terry Love
     
    Last edited by a moderator: Apr 27, 2021
  5. Jeff H Young

    Jeff H Young In the Trades

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    Feb 27, 2020
    Location:
    92346
    unknowns maybe its not OK maybe it is
     
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  6. Tuttles Revenge

    Tuttles Revenge In the Trades

    Joined:
    Oct 15, 2014
    I'm confused.. But it sounds like you described a floor drain with a trap in the slab.. and if its a funnel drain it likely only is 2" under the funnel. So that wouldn't be appropriate for a 3" toilet drain.

    In no circumstances is it OK to drain a toilet or any fixture that already has a trap into a secondary trap in the piping.

    You need to find a suitable 3" drain to connect to for the toilet.
     
    Jeff H Young likes this.
  7. AskingforaFriend

    AskingforaFriend New Member

    Joined:
    Apr 25, 2021
    Location:
    AR
    Thank you, I’m all set. Appreciate the advice.
     
    Tuttles Revenge likes this.
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