What is the general rule or code about a waste line on the outside of the house? I have a "false" (rotting) retaining wall built up on a section of the back of my house which an engineer told me I could take out. As I began that work I came to realize there is a 2"- 2 1/2" waste line from the kitchen running through this bed. If I take out this bed do I have to run the waste through the house now? The foundation is slab and I do no have enough run to run it horizontally in the ground from the point where it exits the house now to where it connects into the main line into the septic. What are my options? Can a waste line be contained in an insulated "box" on the outside of the house?

Afraid you are going to have to say that again. What do you mean retaining wall, what do you mean "bed"?
Generally a retaining wall is a wall built to hold back the earth, soil or something.

There is no code that says the drain must be inside or outside. There may be codes in some places that say the drain line must be protected from freezing. I have seen (in Ireland) the entire stack on the exterior of the building. We generally put drains inside to protect from freezing and for aesthetics but if you want to put it outside, that's all right with me.

Sounds like someone had a problem with the kitchen drain (probably a crushed line under the slab) and ran a new drain outside and ran it under ground to the main sewer line, and boxed it in.

Tell us what you mean by "bed"

Hi hkstroud. Thanks for your reply. This is a retaining wall in the sense that it does have soil behind it and it is about 3.5 ft tall in one place, however, the term bed (as in flower bed) may be more appropriate since it's not structural. Engineers who have looked at it have commented they do not know why anyone would build such a beefy wall (railroad ties 3.5 ft tall) and then fill in behind to the house with soil. Its unattractive and impeding where I'd like to convert a window above it to a door. The iron waste line running through it (coming from the kitchen on the level above) seems a bit like someone being lazy to me. I'm planning to move this into the house and run the waste through the joists, assuming I can get the required drop and stay within the code for drilling joists, but if that can't be done I was trying to determine if there were some general requirements about keeping the line on the outside of the house. I'm searching for additional details in the NC plumbing code as well. Thanks!

I must have been clobbered with a stupid stick. I just spent 15 minutes reading these posts and still don't know what his problem is. As near as I can figure out he found a 2" kitchen drain line that either runs under or through a kind of retaining wall that sets on top of a flower bed. He wants to know what to do with the drain kine after he removes the wall. Then he talks about going in the house and redo the kitchen drain from inside.
I think I'll let you field this one Harold, it sounds too complicated for me.
Good luck with it. Tom