Abandoning Old ABS Drains (But Not Permanently)

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by pollymath, Mar 26, 2021.

  1. pollymath

    pollymath New Member

    Joined:
    Mar 15, 2021
    Location:
    Flagstaff, AZ
    I relocated my shower drain to share a vent with my toilet, all moved across the room from the location of my old tub and shower. Slab on grade, 4" slab over cinders, with wire mesh and rebar and hydronic PEX lines in the slab.

    So I've got a 1.5" trap and a 2" trap with a 2" vent still open at the roof all about 3' from the main stack. Most of that 3' is actually vertical. These pipes wye into the main stack nearly DIRECTLY BELOW them.

    Meaning that in order for me to cut out this whole vent and its associated drains, I'd need to go pretty deep, and that's a BIG challenge. I've already gone about 12" deep to relocate my toilet and that was a huge hassle.

    They are ABS drains, so sealing them is easy.

    My plumber wanted me to cut them off under the slab and cap with ABS cement. Leave the vent open.

    My worry is that if they ever had any problems, finding them would be a challenge.

    I wanted to leave them flush with the floor, with a glued in punch-out test plug, oil in the traps, maybe even a rubber test plug inside. That way, if they ever had problems or we wanted to use them again, we know where they are, and they can be opened up. I don't want to "dynamite" these drains.

    My plumber is worried having those caps visible will spook the inspector, and they could "technically" leak gases into the room once the traps dry out. He felt like having them under the floor was a few extra layers of protection.

    What would you do?
     
  2. James Henry

    James Henry In the Trades

    Joined:
    Jul 23, 2019
    Occupation:
    Plumber
    Location:
    Billings, Montana.
    I would do what the plumber suggests,. Draw a layout with measurements where the drains are, make some copies and put it with your home purchase and mortgage files. The glue in cap is not permanent and the test ball will loose air over time. You can always stamp or imbed something in the concrete where the drain is.
     
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  4. pollymath

    pollymath New Member

    Joined:
    Mar 15, 2021
    Location:
    Flagstaff, AZ
    10-4

    I like the stamp idea, but any marking or layout plan will work too.
     
  5. pollymath

    pollymath New Member

    Joined:
    Mar 15, 2021
    Location:
    Flagstaff, AZ
    Anyone else?

    Should I use some sort of waterless trap seal? Or is the best practice just to cap them under the slab and be done with it?
     
  6. wwhitney

    wwhitney Well-Known Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    Solvent weld capping it is the only reasonable choice short of removal. So the question is whether to cap it under the slab, or whether to bring the cap to the surface of the slab. I don't necessarily see any upside to the latter, but perhaps you do. The question then is whether there is a downside. If you are going to be tiling over that area, definitely put the cap under the slab. But if it's going to be hidden in a dead space (e.g. vanity toekick area), I don't see a downside to a cap flush with the slab.

    Cheers, Wayne
     
  7. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    What are you looking for? Concealment?
    The first one is the worst idea, and the second one does not appeal to me. When you cut the cap off later, you will lose some height. If being sneaky, maybe use a rubber cap, fill the area with sand, and have a thin coat of concrete above the sand.

    Are you trying to hide the fact that you plan to have a future shower there? If not, cap several inches above the concrete. Maybe a clamp around floor drain could be put in at floor level as a stealthy move.

    I am not a pro.
     
  8. pollymath

    pollymath New Member

    Joined:
    Mar 15, 2021
    Location:
    Flagstaff, AZ
    Here's my thinking:

    If ever there was a problem, knowing where the old drains are would be advantageous.

    However, having the drains exposed (but capped/sealed with ABS solvent) exposes them to potential damage and movement. Even if flush with the floor surface and covered with tile.

    Also, having the cap flush with the floor is pointless for trying to allow someone easy access, because more than likely they'd need to chisel into the concrete slab to remove the cap anyways.

    I think the best course of action is cap and seal below the slab, but mark their location above the slab. I could make someone's life easier by thinning out the concrete in that area, but even that isn't really worth it.

    Chances of reusing these drains in future bathroom remodels? Slim, but you never know.
     
  9. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    OK. I was thinking you thought it probable you would use those.
     
  10. pollymath

    pollymath New Member

    Joined:
    Mar 15, 2021
    Location:
    Flagstaff, AZ
    Thanks for the help all. I solvent welded the caps below the slab and will mark their location somehow on top.
     
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