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Thread: Correct method for connecting to a 4” Cast Iron shower drain?

  1. #1
    DIY Junior Member SBG's Avatar
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    Default Correct method for connecting to a 4” Cast Iron shower drain?

    I am currently remodeling a bathroom in my house and need some guidance on the shower drain. The house is located in Lake County, Illinois and was built in 1967. It is a “tri-level” and the shower is located on the lower level, on the concrete slab.

    The original shower tray was cast concrete with some other patterned material cast over the top of that and a steel “border”. While contemplating how to remove it, I forced a pry-bar under the tray and was able to lever the entire thing off the floor. An inspection of the underside showed a couple of cracks and the concrete slab underneath was saturated. This saturation also wicked into the footer of the wall framing, rotting it out together with the attached drywall turning to powder. It was a nice mess

    The part that amazed me most was there being no proper coupling between the shower tray and the drain hole in the floor. The shower tray was simply laid over the top of the drain with apparently no means of sealing one to the other. Was this common practice in 1967?

    The other thing which seems odd is that the drain is 4” CI pipe that is simply flush with the floor, with no flange – see photo below. I guess it will likely never get blocked, but the 4” drain is where my pain is.

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    I would like to use the Schluter shower tray system and they actually offer a Drain Adaptor kit that will bolt on top of a standard 2” shower flange…but, of course, I don’t have a flange and my pipe is 4” CI.

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    I came up with the idea of using a Closet (toilet) flange. Oatey offers a good selection of these things, many designed to be retrofitted into existing 4” CI pipe. These two, which fit on the inside of the pipe, have to deal with a very rough surface. Even if I can get the pipe clean enough, there will be extensive pitting and I wonder how well these will seal.

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    http://www.oatey.com/products/drains...-closet-flange
    http://www.oatey.com/products/drains...-closet-flange


    This flange fits over the outside of the pipe, but requires hacking into the concrete. I’d imagine the outside of the pipe is far smoother than the inside,

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    http://www.oatey.com/products/drains...-closet-flange


    So, my main questions are:

    • Is using a Closet Flange permissible for a shower application, or is there some other special fitting available which converts 4” CI? If so, then…
    • With any of the Oatey flanges, I need to get the Schluter adaptor ring to fit to the top of the flange face. I’m sure I could use KerdiFix and some bolts to secure the adaptor to the flange, but is this a valid approach?

    Thanks!

  2. #2
    Forum Admin, Expert Plumber Terry's Avatar
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    You will need to break out the floor and attach a proper shower drain or pain.
    Concrete is not a proper means of installing a shower pan. There should have been a liner below the concrete that in conjunction with a clamping shower drain. Concrete is porous.
    Most shower drains are 2", so I would break out the concrete and use a reducing coupling with a section of 2" pipe for the new shower drain.

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    Moderator & Master Plumber hj's Avatar
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    Default ddrain

    It apears you had a "precast terrazzo" base which rusted away. The way it was installed over the trap was NEVER an approved method, but would have been how a DIYer might have done it over a floor drain. Installing a closet flange, of any kind, will not make your job easier or more "legal"/proper.
    Licensed residential and commercial plumber

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    DIY Junior Member SBG's Avatar
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    Terry,

    Thanks for the quick response.

    I kind of feared this would involve busting up the concrete, but I'd rather do it right. Hopefully, it shouldn't be too painful.

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    DIY Junior Member SBG's Avatar
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    Quote Originally Posted by hj View Post
    It apears you had a "precast terrazzo" base which rusted away. The way it was installed over the trap was NEVER an approved method, but would have been how a DIYer might have done it over a floor drain. Installing a closet flange, of any kind, will not make your job easier or more "legal"/proper.

    Ah... "precast terrazzo"...so that's what it was (confirmation courtesy of Google). I did enjoy smashing it to pieces and I'm fairly certain the house was built with this pan. Amazing what they got away with back then.

    Per Terry's comment, I'll do this the "proper" way and use a 4" -> 2" reducer together with the correct shower flange.

    Thanks for your input.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    If you reduce it to the normal 2" (I'd probably use pvc), you can then use the 'normal' glue-on Kerdi drain.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member SBG's Avatar
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    Thanks Jim,

    Yeah...I think I'll go for the 2" PVC which will make connection to the Kerdi drain easy. Still amazed that anyone would think a 4" pipe was necessary for a shower, unless you were bathing a baby buffalo or something like that.

  8. #8
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Here in Vancouver a floor drain in 3" does not need a vent. May be that your shower drain has no vent.

    I might keep to a 3" drain just to be safe. JW


    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.

  9. #9
    DIY Junior Member SBG's Avatar
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    Now that's an interesting thought. The floor drain is located within 2 feet of the main stack (which vents to the roof), but has no separate vent for itself. I should probably have a look at the Illinois code and see what it has to say.

    Technically, I'm only changing the last few inches, specifically so I can get the 4" drain to fit a standard 2" flange. Does this still qualify as a 4" drain if I do this?

  10. #10
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    If it's 2' away to the stack I'm sure you are OK.

    Quote Originally Posted by SBG View Post
    Now that's an interesting thought. The floor drain is located within 2 feet of the main stack (which vents to the roof), but has no separate vent for itself. I should probably have a look at the Illinois code and see what it has to say.

    Technically, I'm only changing the last few inches, specifically so I can get the 4" drain to fit a standard 2" flange. Does this still qualify as a 4" drain if I do this?


    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.

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