Toilet flange for odd-size drain pipe

[MIkeUva]

Hi! I would like to bolt a new closet flange directly onto a concrete floor (basement). The interior surface of the hole leading to the drain is bare concrete, to a depth of 3.5" inches, where there is an old plastic (PVC?) lining flush with the concrete above it.
The diameter of the hole (all the way down) is 3.75". As such it does not accommodate a 3" or 4" diameter PVC. The flanges I've looked at would either bee too big, or would not fit snug against the concrete interior of the hole.

How would you approach this? Thank you for your recommendations!

 

[bbp]

That looks like a drain tile and not a waste line. Flush another toilet and listen for it in that pipe.

 

[MIkeUva]

That looks like a drain tile and not a waste line. Flush another toilet and listen for it in that pipe.

Hi, it's where the old toilet was hooked up (poorly) leading to leaks and damaged floor, replaced by concrete.

 

[CT18]

Someone jerry rigged that thing. The pipe is down low in that opening. Break up the floor and find out what is going on there

 

[Jeff Handy]

At the very least, you need to chip off the concrete at the top left of the hole, to make it round.

 

[Jeff Handy]

It looks like a new 3.5 inch floor might have been poured right over an older floor.

 

[Jeff Handy]

I think a 4 inch sch 80 pipe has that ID of 3.75.
Not certain.

 

[frodo]

that is a clean out or floor drain i see the threads in the picture

shove a tape measure down the pipe and ''feel'' it it goes around a 90 or goes around a p trap

if it is a 90. it is a co if it is a trap it is a floor drain

 

[Pat the Plumber CIL]

If you are confident a toilet has worked there in the past there is a repair / extension flange you could seal with silicone and secure with tapcons to the concrete . Ideally a 4 inch pipe (inside diameter ) sticks up out of the concrete . Then a 3 inch toilet flange can be glued to the inside and then secured to the slab .