I want to put a bathroom in my basement. The main drain line is under the basement floor in the concrete. I know that I will have to bust up the floor some, but how do I tie the new bathroom drain pipe into the current pipe? Can all of the new drains (shower, sink and toilet) go into one line that ties into the current drain pipe?

I want to put a bathroom in my basement. The main drain line is under the basement floor in the concrete. I know that I will have to bust up the floor some, but how do I tie the new bathroom drain pipe into the current pipe? Can all of the new drains (shower, sink and toilet) go into one line that ties into the current drain pipe?

You will cut in a wye or a combination wye and eighth bend in the main to pick up the toilet drain line, (4" in my area).
The hardest part about installing a bathroom in a "add on remodel job" is the drainage and venting. The floor has to be jackhammered up and the sewer main located. Then after you branch off the main you have to jackhammer the cement up and trench to pick up each fixture. Water will also have to connected and laid in the trenches to supply the fixtures. A bathroom group vent will then have to installed off the lavatory and go through the roof or revent back into a existing vent in the attic. In a two story house this can be a real hassle. Then the basement floor will have to be patched and tiled over to hide the patches.
Let me show you a typical, (in my area) bathroom group rough in. This configuration only uses one vent for the entire group.
4" ,(under cement and basements) 3" (on first and second floor) from the toilet to the main. The lavatory to connect to the toilet drain line and vent to the roof or revent back in the attic to a existing roof vent. The tub/shower to connect to the lavatory drain line and be wet vented by it as will the toilet. Be advised to always check local codes before changing or remodeling your drainage system. Good luck, Tom

Best if you post a sketch of your project and we will draw it for you into your sketch...