My house is a bit of a strange design. Although the living room appears to be an addition to the home, it was actually built at the same time as the rest of the house. Looking at the front of the house, the living room is the left 1/3 of the house and has a "crawl space" and the rest of the house is built on a basement. The basement has 9ft ceilings and has a door that opens to the area under the living room. The area under the living room is about 11 ft high. Stepping out of the door, the ground is about two feet below the level of the basement floor.
There is currently no plumbing in the basement, so the main drain pipe coming from the house above extends through the wall into the area under the living room, and then drops at about a 45 degree angle and extends across the length of the living room and exits at ground level on the other side of the living room (left-most wall of the house). I would like to add a restroom in the basement and wondered if there would be any problem connecting the drain pipes directly to that angled dropping pipe as long as I stay above the lowest point of the pipe?
Here's a rudimentary diagram of what I'm talking about:
I'll not be doing the work myself as I know my limitations, but I would like to get an idea if this is feasible and if there are any gotchas I might need to be aware of before I bring a plumber in to look at it.
Thanks in advance for any pointers you might have.