My house had an option of a second bathroom. The original owner did not go for this option & the plumber put cement in the hub of a 3 inch cast iron waste pipe. I want to now add the second bathroom and I need to use this pipe since it is in the right location. Running a new pipe is out of the question since I am on a concrete slab. There is a kitchen sink located three feet away from this pipe which makes me believe that this pipe is not totally dead. My questions are: Do you think the cement is just at the hub? Or further down the pipe? Is it possible to get this cement out & how? So that this pipe can be used...

Thanks,
John

It is likely the cement is just in the first few inches and I'd give a try at removing it. Get a hammer drill and a good masonary 1/2" bit. Drill 3-4, or more, holes in the cement near the edge. Do not chisel until you have broken loose the cement core. You need to fish out all of the cement chunks.

Bal gave you very good advice. The cement is probably just a plug. You now have your main drain. Let m e give you the details of a typical bath installation. Most bathroom groups are roughed in like this.
Toilet connects to sewer main or the stack vent. Lavatory connects to toilet drain and runs a vent off the top the stubout tee out the roof or revents back into a dry vent in the attic.. The toilet wet vents through the lavatory vent and the tub/shower connects to the lavatory drain and is wet vented by it. This is a normal rough in and is acceptable both by local and state codes and also The Standard Plumbing Code Book in 90 percent of the country. Check your local codes.to make sure you're not in the excluded 10 percent. Good luck, Tom