A local plumber is really needed at your house. He has the answers you seek.

Thanks for replying, bus_driver. I was hoping that someone might be able to say whether it's even allowed for a waste pipe to have any bends before asking someone for an estimate.

the answer is yes, to the question that you phrased, as to whether a drain pipe can ever have a bend in it. You've seen drains with bends in them before, no doubt. I confirm to you that what you saw really was a drain pipe that bended. The question you asked was general. No-one will ever say that adding unnecessary bends is a good thing to do, so you may meet up with a lot of resistance along the lines of "it's not ideal." But don't let that deter you from studying your options. In the end you will have learned a few things, and maybe you will have found some way to make something work better in your proposed basement floor plan.

Vertically a bend has to be a long sweep, which takes up a lot of space, so you may find that you are not happy with the options you will have since your ceiling height is only about 7' to start with. In other words, to get that pipe out of the way might mean you begin re-routing it from a much higher point, somewhere in the wall of the ground floor (above the basement.) Fun, fun, fun. Money and risk.

hope this helps.

"Vertically a bend has to be a long sweep"..That is not true. in fact, with the singular exception of a water closet ALL connections to a horizontal line MUST be made by means of a Wye & 1/8 bend or Combo'

There must be a clean out at all changes in direction which are 45deg or greater and a clean out on the upstream end of all drain lines.

A long radius bend as was suggest above is prohibited.

Before the line in question can be moved ever line attached to it must be identified as either a Vented Branch or a Fixture Arm. If any of the lines are Fixture Arms you much check to insure the proposed change would not extend the fixture arm longer than the code permitted length for the fixture arm line size. If the new TDL (total developed length) exceeds the code maximums you would be required to install an auxiliary vent on the fixture arm.

If the proposed change alters the total overall length of the line the entire line would have to be re pitched.

Thanks. It sounds even more complicated than I imagined. But at least it sounds like it can be done. I'll get a plumber to take a look at my situation.