Recently I started a thread to get advice on how to move a flange for a toilet so that I can wind up with a 12" rough-in when I'm done. It's problematic since I can't really work with the ABS under the floor. It wasn't done properly and has the drain for the tub, the sink and the toilet all going into the same toilet drain. See photos below. To do it correctly would cost around $5K, according to a quote we got from a plumber recently.

To summarize from my previous thread I removed three layers of linoleum, two layers of fir planking and am now down to the bare joists. I cut away the flared portion of the flange and as you can see the hubs for both the ABS align with the hub of the offset flange. Meaning, they are both four inches in diameter. Also, now that so many layers of flooring has been removed I am wondering if I can shave off a bit of the hub from both the ABS drain pipe in the floor along with removing part of the hub from the offset flange to help bring it down lower. The hubs on both measure 1.5" in length. If I can remove an inch off of each hub to eliminate two inches and be left with just one inch to work with this would help a lot.

I thought I could buy some ABS piping that could fit inside both the flange hub and ABS hub in the floor. It would basically be a one inch ring connecting both hubs from the inside.

Once I put my 3/4" plywood over the joists, cement sheet rock and possibly a leveling compound followed by 1" hexagon porcelain tile I am confident that I can get the metal ring of the offset flange to sit flush against the new final height of the floor.

But I am wondering if my idea is bad one or if anyone can suggest better ideas. I really want to use the offset flange to not only give me about an extra inch from the back wall but also want to place it diagonally to allow an extra inch away from the side wall. It's a bit too close to the side wall. This is a 2" offset flange, by the way.

I've also included a very bad drawing to help provide a visual as far as getting my idea across without any confusion.

A summary with pics:

Here is a pic of the old flange in place: enter image description here

After sawing off the flared portion of the flange I am left with this: enter image description here I am going to attempt to carefully grind away the rest of the flange that is bonded on the inside of the ABS in the floor to be able to re-bond the new ABS "ring" I will cut to size to connect the new offset flange in place.

Another angle where you can see all the the other ABS drain lines that connect to the toilet drain line: enter image description here ^ This is why I simply can't just extend the horizontal portion of the ABS under the floor to give me a 12" rough-in. I' have to redo all the drain pipes that connect to one drain. It would be a real pain.

Setting my new offset 4x3 flange on top of the ABS hub in the floor. They are the same diameter: enter image description here

My (very bad) drawing summarizing what I am trying to do: enter image description here

After sawing away the old flared portion of the flange I can see that only about a half inch of ABS from the old flange made a permanent bond with the ABS drain pipe in the floor. So this is why I am wondering if I can make the hubs a half inch in length and create a "ring" with ABS to fit inside each one to make this work.

Hope to hear back and get some input, thanks!

  • Yiu can buy toilets for different size rough in
    – Kris
    Mar 6, 2018 at 13:40
  • Modifying ABS fittings by cutting away two thirds of the glue joint area is a big hack and leading to a large risk of joint failure in the future. I recommend not doing this. As others have suggested....get a toilet with the suitable dimension.
    – Michael Karas
    Mar 6, 2018 at 14:20
  • From your original post, I think, and I must say that's some gnarly drain setup, that you should cut all the drain assemblies at the wye's and redo just that small section and move your toilet to the 12" RI you need. You are maybe looking at $30 in parts, maybe less. This also allows the water to flow away from other drains upstream. While at it, convert the 45 degree 2-way wye to a 3-way (double wye)and eliminate the extra pipe curve to the pipe coming from the top of your 3rd picture.
    – Jeff Cates
    Mar 8, 2018 at 21:16
  • It's pretty crazy. The extra drain pipe you mentioned in the third photo is from the unit next door. I am not sure what it drains from but I'd have to put it back somehow after I'm done.
    – Adrien
    Mar 10, 2018 at 20:10

1 Answer 1


You can get a flange that fits inside a 4" pipe, or if you remove inside get one that sits inside a 4" hub.

  • But this isn't going to be an offset flange that will allow me to make my current 11" rough-in to a 12" rough-in, right?
    – Adrien
    Mar 6, 2018 at 22:00
  • The offset alows for more than a inch
    – aofkj
    Mar 7, 2018 at 2:30
  • Can you provide a link to one that I buy online? I haven't seen one anywhere.
    – Adrien
    Mar 7, 2018 at 15:34
  • Thanks for providing a link to that flange. But just to be clear, the outside diameter of the ABS flange is 4". The inside is 3.5" once I grind away what's left of the old flange that I cut off. The product you linked me to says it has an outside flange of 4" also. So not sure how I can make that work for my application.
    – Adrien
    Mar 10, 2018 at 20:08

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