Size of Plumbing Drain Pipes

[woodworker2000]

What is the "standard" size for a drain pipe for a toilet and for a sink? I am considering finishing out my walk-up attic and thinking about putting a bathroom in it. When I had the house built, I had the builder run 3 3" PVC (schedule 40) pipes from the basement to the attic. At the time, I was thinking that I might use them for electrical chases but now I'm wondering if I can use one of them for a drain pipe for a bathroom in the attic. My first question is whether 3" pipe would be sufficient for a toilet dran and a sink drain. My second question is whether I can use one 3" pipe for both the toilet and the sink.

A related question (which might have to go in the electrical code forum) is whether I can use one of the pvc pipes as a chase to run NM wire and telephone and data cable (from the basement to the attic). Of course, I would only be able to secure the cable at the entrance and exit of the chase and couldn't secure it while it is in the chase.

Thanks.

[homebild]

Minimum drain pipe size for a water closet is 3"

Minimum drain size for a lavatory is 1 1/4".

You could use a 3" pipe to drain both.