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Thread: How to seal a closet flange in concrete...

  1. #1

    Default How to seal a closet flange in concrete...

    Wow - Great forum. I'm glad to know there a more that just me monkeying with their plumbing. Anyway, I've learned a bunch, but not what I need.

    I was hoping some one could tell me if there is a way to seal off a closet flange where a toilet used to be. I've extensively remodeled a basement moving the bathroom to the other side of the house. That leaves a closet flange sticking out of the concrete where the old toilet used to be. Rather than excavate through the concrete, I'd rather just seal it off where it is- if possible. Once finished, the new floor height will give about 1.25' of vertical clearance above the old flange. There'll also be cabinets over the flange, so I guess if necessary, I could cut into the bottom to provide extra clearance.

    Any ideas?


  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    There are expandable rubber plugs that would work for this. The ones I'm thinking of have a bolt through them. You tighten it up and it squeezes tight to the sides. See if the pros have any better thoughts...
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    Consultant cwhyu2's Avatar
    Join Date
    Aug 2007
    Cincinnati OH


    First off what kind of pipe is the flange attached to.I would remove the flange
    and cap it with a proper cap.It may require some chipping of the concrete.

  4. #4


    I assume the flange is attached to a closet elbow. Its hard to tell for sure because everything is burried in concrete, except the top of the flange itself. I was thinking that since the subfloor height will be 1.5" around the flange and over that will be a toe kick space under a cabinet, I could use the 4 or so inches to do something else. Hopefully something that doesn't require chiseling more concrete.

    I like the expansion plug idea but I'm not sure if something like that will work?? Any thoughts?


  5. #5
    Plumber Sandpiper Plumbing's Avatar
    Join Date
    May 2008
    Northern by birth, Southern by choice


    Ideally, the best thing to do would be chip up the concrete a little and glue on a hard cap. The expanding plugs use a tapered rubber plug which will degrade over time, eventually crack/crumble and will not seal.
    I've seen guys do the quick and dirty method, shove a piece of wire mess down the pipe a little and fill it with quick-setting concrete but still not the best idea.


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