I'm installing subfloor on existing concrete slab. I've removed the toilet and the flange is flush with the slab and appears to be glued in place to the pipe. How can I extend the pipe 1 and a half inches or so to accommodate the subfloor I wish to install and the new flange for the toilet post-sub-floor-installation? Thanks.

 

I should have added that this is plastic pipe and flange. I've been told that it would be best to cut the flange out of the slab and then find pipe that will fit inside the existing pipe in the slab to extend the pipe up above the level of the sub-floor and allow installation of a new flange. Any advice or suggestions on possible pitfalls of that solution would be welcomed.

 

hawkjet, Welcome to the DIY Forums.
1-1/2" is quite a bit. If you have 4" pipe to the original flange, you could put a 3" to 4" reducing flange on it. If the pipe is now 3", you would probably have drainage problems later if you reduce it any more. I am not sure of the largest thickness of flange extenders.(they can be stacked) These are used to raise the height of the flange for ceramic tile. They have a bonding substance on one side to make a seal against the original flange. Flange extenders still have to be secured to the floor through the 4 holes in the original flange and the extender. Hope this helps. Good luck.