How should I repair a pvc flange set into concrete slab?
I would install a toilet Flange repair ring. This is a metal ring you mount on top this method cost about 10$. The other route is to cut the old flange out and install a new compression flange. This method cost about 35-40$ and is more work but the advantage is it works well with the new height of the flooring. Both methods work but I prefer the compression flange when changing flooring height.