I have existing rough in plumbing in my basement. I would like to connect a new
Toilet to an existing 3" PVC pipe that extends about 18" in the air. What type of connection do I use at the floor level? The PVC is covered with tar paper as it disappears in the concrete.

You need to cut that pipe an inch below the floor and weld/glue in a toilet fange. Adjustable Level-Fit Closet Flange :: Oatey.com (http://www.oatey.com/Plumber/Shared/ProductGroupDetail/105/Adjustable+Level-Fit+Closet+Flange.html)

You need to cut that pipean inch below the floor and weld/glue in a toilet fange. Adjustable Level-Fit Closet Flange :: Oatey.com (http://www.oatey.com/Plumber/Shared/ProductGroupDetail/105/Adjustable+Level-Fit+Closet+Flange.html)

How do I cut the PVC 1" below the concrete? Isn't there something out there that I can just glue to the inside of the pipe at floor level? I am able to drill holes in the concrete to place anchor bolts in to hold this in place.

Are you building up the floor with a sub floor and tile? You can install a flange that fits inside the existing pipe but that flange may still be just a hair to tall. Chipping away the concrete to creat a flush mount is usually the route to follow. Tell me about your ideas for floor finish.

Are you building up the floor with a sub floor and tile? You can install a flange that fits inside the existing pipe but that flange may still be just a hair to tall. Chipping away the concrete to creat a flush mount is usually the route to follow. Tell me about your ideas for floor finish.

The existing floor is concrete. I will be using ceramic tile to finish the floor. If the flange
Is 1/4" - 1/2" thick I can build up the floor to match this height. I would prefer to do anything that works that does not require me to break up any concrete.

Here is the issue. Take a close look at the falnge I posted. If you had a 4" pipe the flange would fit inside the pipe like you were hoping. However, you have a 3" pipe so the flange fits over the pipe. You need to chip away enough of the concrete to make room for the neck of the flange. I am not talking about busting a hole in the floor but this chipping should only require a masonasry chisel and a small maul and about 5 minutes.