Existing toilet flange sits on top of a 4" diameter ABS down section of approximately 10" in length before it turns 90 degrees and I assume runs horizontal to join the drain line that the other two toilets are connected to
The drain lines are located below a 5 to 6 inch thick concrete slab that the house sits on.
For a City Permit to add a second toilet in a room ( 4 feet from existing toilet), the existing toilet must be connected to a 4" line that runs to the city road.
QUESTION: Is there a method of measuring diameter of the buried horizontal line that is connected to the exit end of the 90 degree elbow?

Is there a method of measuring diameter of the buried horizontal line that is connected to the exit end of the 90 degree elbow?
You have already answered your question with;
Existing toilet flange sits on top of a 4" diameter ABS down section of approximately 10" in length
Most codes mandate that water closet drain lines be 4" under the slab. Regards, Tom

Hmmmm...

Inside diameter of 4" ABS is 4"..

Outside diameter of 4" ABS is 4.5"..

Alan, remeasure the O.D. of the pipe again... give us the EXACT measure, OK?

Mark

Hey Mark,
This should have been a "no brainer question. Either 3 or 4" under the slab. Unless he had a 3 X 4" closet bend he had 4" under the slab.
However, you picked up on something else and you've got me wondering what it was. Regards, Tom

I agree, Tom. Almost no question the main is 4" under there, but that O.D. Alan presented is right in between 3" and 4" ABS..

Curious is all...

What am I missing Mark?

Existing toilet flange sits on top of a 4" diameter ABS That's the only figure that I can find and I'm sure that you don't think the OD of 3" ABS is 4". So once more, what am I missing? Cheers, Tom

I took the 4" diameter literally as 4" outside diameter... no such outside pipe diameter...

Either 3.5" diameter (3" pipe) or 4.5" diameter (4" pipe)... just want to know which it is, is all!

Mark

I took the 4" diameter literally as 4" outside diameter... And I took it to mean inside diameter. My bet's on the 4" ID. Don't see how it could possibly be anything else. Hey! to me, 4" means 4". Have a great day, Tom