Hi all. I would like to move my toilet 34" across to opposite wall for better bathroom layout. I chipped out the concrete around existing cast iron closet flange to see what I was dealing with under slab. Wanted to measure distance from top of closet bend arm to slab level, so that I could determine if there was enough grade to move the toilet location and maintain proper drain slope/pitch.

So, it looks like a 4" cast iron closet bend. Measures just over 3 1/2" from top of vertical pipe arm to slab level above. Pic below.

In order to move the toilet flange 34" straight across to other side(see pic showing new location), I will need to maintain proper drain slope. 4" pipe, which I believe calls for 1/8" per foot minimum slope. 34" is just about 3 feet... so 3/8" total rise/slope over this distance to new flange.

My Plan - and the issue:
So lets say I cut the vertical closet bend arm, I use a Mission Rubber MR56 44 ARC hub to transition the horizontal 4" cast iron to 4" ABS DWV pipe (California). Then I glue on a 4" ABS 90 HxH elbow to come up above slab. Glue in a 4" vertical pipe and run it wild above slab about 5". Cap it. Patch trench with concrete. Tile floor (1' x 2' large format). Cut riser pipe flush with finished tile floor, and then glue new closet flange into 4" ABS riser pipe... with metal flange ring sitting on top of finished floor.

My issue/question...
To maintain proper slope (about 3/8" to 1/2" rise over the 3 feet drain extension), the top of the plastic 90 elbow will sit 1/2" proud of the slab floor after trench is patched with concrete. See my drawing below that illustrates this.
Is having 1/2" of the ABS 90s hub exposed above slab a problem? Like a code violation, or other issue?

Since I will be tiling the floor with large format tile (1' x 2'), the finished floor will end up at least 5/8" higher than slab level... so that top part of the elbow sticking out 1/2" above slab would be covered after tile. Seems like a non issue, so as long as closet flange seats into pipe and sits flush on top of finished tile floor.

Is my plan sound? Am I missing something? Is 1/2" of the elbow sticking up above slab level an issue? Thank you for any tips or advice here! Would be nice to be able to move this toilet and improve layout.
Pics @ album link below, so I don't clog up forum:
[www.thegearpage.net]

No problem with the hub sticking up 1/2".

Thanks, Steve. I didn't think it would be an issue... but looking to be sure that everything is good before moving forward with cutting slab.

And am I right with the 1/8" per foot slope for 4" drain pipe? I believe that is what UPC allows for when using larger than 3" for horizontal DWV.



Edited 1 times.

708.1 of the 2022 CA plumbing code states that with prior permission from the AHJ, 4" and larger diameter can be run at 1/8" per foot. Personally I don't see that short span causing an issue. You could also adapt that run to 3" and use either a 3" elbow or 3x4 closet bend under the toilet. It is legal to reduce the toilet riser from 4" to 3".

I did think of running 3" with the 3"x4" closet bend. Saw that closet bend at Homer and it got me thinking.
I suppose I will commence with cutting the slab, then see what makes the most sense. I'm sure I'll be back to post after opening up a trench. Thanks again!