As e-plumber said, there will be a 3inch drain pipe or larger under the floor. If you see a waste pipe running down your wall, etc. into the floor, you will want to tie into it. This will involve a lot of effort and expense, such as excavating the floor, installing new pipes under th4 floor, etc. It would be wise to consult a plumber, if you are inexperienced.

: : I have laundry in my basement, and a sink. The only plumbung drains are a floor drain and a pipe sticking up from the floor. How do know if this drain is ok for putting in a bath or just a shower. My home was built in the 40s.

: Reply:
: You would need at least a 3" pipe underground to have a toilet installed, you do have one, the question is how far away is it from the proposed basement bathroom? Only a licensed plumber would be able to advise you after seeing the conditions.
: Good Luck. e-plumber