In our (badly designed) flat the upstairs waste pipes run straight through our bedrooms.
It's a shame as the outer corridor is right next to our bedroom, so it would have been sensible to put it in there.
Any recomendations on sound proofing a waste pipe?
EDIT:
Thanks for BMitch's answer, I forgot to add the information that the waste pipe is already enclosed.
Best Answer
If the pipe is exposed, you can enclose it with a small wall (several 2x4's for the framing and a little drywall). Make sure at any cleanout openings, you include an access panel in the wall. Then, before you install the drywall, put a bunch of insulation in there, surrounding the pipe. Avoid having anything solid connecting the pipe to the wall since that will transmit sound.
Edit: A post construction idea is to hang something that absorbs sound on the wall, such as an acoustical panel frequently used for home theaters or even a tapestry.