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Thread: New Toilet Flange, Stone Slab Floor

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  1. #1
    DIY Junior Member zmonk's Avatar
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    Default New Toilet Flange, Stone Slab Floor

    Hi. I'm hoping somebody has encountered this situation and may have a suggestion.

    The floor in our 2nd floor bath is a mashup. Most is 3/4" plywood, with some concrete sections around the borders. The toilet sits on a slab of some sort of stone -- slate or bluestone perhaps. It does flake. As you can see, the old flange has been removed from the drain pipe, which appears to be made of lead -- it's very soft. The pipe is not centered in the hole that has been cut in the stone, and it cannot be moved.

    The stone slab is about 3/4" thick, and cut on an angle that increases the interior diameter from top to bottom. In other words, if the diameter of the hole on top of the slab is 5 inches, it flares out to a larger interior diameter at the bottom of the slab. It appears to be resting on the floor joists, so there is air underneath it.

    A compression flange that fits around the exterior of the pipe does not appear to be an option. I could chip away enough of the slab so that it could fit around the pipe, but then it has nothing to sit on. My only option seems to be a pvc Sioux Chief flange with a metal reinforcement ring that fits the interior of the pipe and seals with a 3-ring rubber flange.

    I would like to fasten the flange to the stone slab at three points, taking into account the fact that at least one of the fastening points will be close to the edge of the stone, so I need to cut clean holes in the slab, without destroying it. Then I would use toggle bolts to tighten down the flange. (By the way, the floor will be finished with 1/4" backer board and 1/8" ceramic tiles, all secured with modified thinset.)

    Is there a tool that can give me a clean hole through the slab? If not, does anybody have an alternative solution? Thanks in advance.

    Howard
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  2. #2
    DIY Senior Member BobL43's Avatar
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    Here is an old thread with a similar? situation

    http://www.terrylove.com/forums/arch...hp/t-4974.html


    drilling holes to anchor the flange to the slab, if you are going to re-use it, it the easy part by using diamond tip hole saws.
    Last edited by BobL43; 12-10-2012 at 09:32 AM.
    I am definitely not a pro plumber, but I am a pro crastinator

  3. #3
    Test, Don't Guess! cacher_chick's Avatar
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    If you have a lead closet bend, NO ABS or PVC flange is going to seal to it. This needs to be done right, or you are going to have a leak. Without seeing what is there, it is impossible to say what needs to be done.

  4. #4
    DIY Junior Member zmonk's Avatar
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    I guess the proper solution would be to extend the drain with some sort of collar and then lead caulk a new brass flange at floor level. Unfortunately, that's beyond my skill level. Here's the unit I plan to install

    http://www.siouxchief.com/Drainage/R...ush-Tite.VZ8US

    The 3-rib gasket fits very snugly; the plastic down pipe can be trimmed to accomodate the bend. And, yes, the diamond tip hole saw looks like a winner. I found one at the local tool rental in 5/8". I'm just hoping the slab does not shatter drilling so close to the edge and that the plastic flange holds up under daily use. I have read posts on the web from others who have used non-metal flanges successfully . . .

  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
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    If you want to do this right, you need to tear more out than you're currently planning. CBU is not specified for use over cement (or stone) - it is designed to be screwed down to plywood. It MUST have a layer of thinset underneath it as well. The purpose of that thinset is not to anchor it, but to fill any imperfections and provide 100% support to the floor tile above. In addition, it provides a compatible surface for the mortar to hold the tile down.

    Way back when, places required a stone piece underneath the toilet to help ensure it didn't fall through the rotten wood if the silly thing leaked (and lead was more prone to that than modern equivalents).

    You have not indicated if you evaluated the floor for proper strength (deflection ratings) to determine if it could even support tile properly.

    With your mix of wood and concrete, old leaded pipes, and who knows what, you are at big risks for a successful remodel!

    None of the expansion toilet flanges are designed to work in a leaded pipe. The lead is highly unlikely to be nice and round, and getting a proper seal is very unlikely.

    If you don't want to be redoing this shortly, you need to rethink what's going on and how best to do it right.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  6. #6
    DIY Junior Member zmonk's Avatar
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    Okay. First of all, thanks for the input. But this is not an expansion flange, just a passive triple gasket seal. Granted, it may not last forever (what does?), but I don't have a lot of options at this point. The floor had ceramic tiles previously, which I removed, so no issue there. The backerboard will be fixed to the floor materials with modified thinset and a combination of ribbed waferhead screws (as per manufacturer's instructions) in the plywood sections and coated tapcon screws in the concrete and stone sections. Which brings me to the point of this post.

    I was all set to spring for the 5/8" diamond tip hole saw, but decided to mark the drill locations in the stone first, so I could see how close to the edge of the opening the holes would come. Nothing I had was leaving a decent mark on the stone, so I decided to use a conventional drill bit, just to make a scratch. That's when I discovered that the slab is made of a very soft stone, easily drilled out and capable of holding a tapcon concrete screw securely. I figure I'll drill pilot holes (5/32" I believe) and sink four or five of them through the tile, thinset, and backerboard, deep into the stone slab. That ought to hold the flange tight and flush with the tiles for as long as the plastic and the gasket will last. And if it dies before I do, it'll be easy to replace.

    Any ideas as to what type of stone this might be? Dark blue/gray in color, very soft and powdery when you drill into it . . .

  7. #7
    In the Trades Gary Swart's Avatar
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    This is a DIY forum, but sometimes the best advice is to hire a professional. I believe this is one of those times. There is NO quick, easy fix for what you have, and there are skill required to do the job right that you do not possess. That's pretty blunt I know, but we all have our limitations. We just need to know when it's time to admit them.

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