Leaky toilet riser in concrete floor

I installed a 4" ABS DWV riser when I poured the concrete for my basement floor. After it all cured, I cut the pipe flush with the floor, and glued in a toilet flange inside the 4" pipe (with a knock out to enable leak checking). When I filled the vent stack, water gushed from below the flange (bad glue joint?). I knocked out the removeable plastic, and stuck an inflation ball 8" down into the 4" pipe to complete my stack test, and all held fine. Now, how do I fix the bad glue joint? Ideally, I'd like to cut off the top 2-3inches of the riser including the bad flange (from the inside of the 4", not busting any concrete), find a long tail 3" insert, and some kind of flexible donut seal outside the new 3" and inside the existing (embedded in concrete) 4" riser. I have 18" of vertical 4" below the floor. Any help or advice is appreciated. Thanks

If it's an inside fit flange, you should be able to cut a few slices in the inside of the flange and break it loose from the pipe.

If you need to cut the riser, you have plenty of riser pipe to allow you to cut it off and install a new section of 4" pipe with a coupling. You will need to chip away enough to get the coupling down the hole. A shop-vac with a small diameter hose works wonders when cleaning out the area around the existing pipe.

I`m sorry man but you might have to get the jack hammer out.
That being said,it must be from the flange glued into the 4" pipe if there are no other fittings between the
flange and the 90 deg ell 18" below the finished floor.
You can try to cut out the inside flange and install a 4" over the pipe flange.
There is no donut or 3" flex pipe that will help you.

Like Casher Chick mentioned, it can be split out if you cut the flange off, and then cut a portion out of the inside and then take a flat blade screwdriver and continue on around splitting it out.

any experience with this fix? Oatey 43650

Terry said:

Like Casher Chick mentioned, it can be split out if you cut the flange off, and then cut a portion out of the inside and then take a flat blade screwdriver and continue on around splitting it out.

Click to expand...

This part looks like it might seal against a scuffed interior wall of the 4" embedded pipe after I break out the bad glue joint. Any thoughts?

Purple primer will soften and smooth out the surface. Brush it in thoroughly before you glue up a new flange.

Good PVC flanges have a stainless steel mounting . The all plastic ones tend to crack.

The link you provided is being blocked. Here is a link to Oatey's site. The product is listed for use on cast iron, not ABS.

Purple primer is for PVC.