Custom Pipe Rule that checks to see the angle between pipes and checks to make sure wall thickness between pipes along the outside structure wall is allowable.

Steps

1. Make a copy of C3DPiperules.xml and replace with this one: C3DPiperules.xml (the folder location is C:\ProgramData\Autodesk\C3D 2009\enu\ in Vista, don't recall what it is in XP)
2. Copy this file in the same folder that the C3DPiperules.xml was in: C3DCustomPipeRules.dvb
3. If Civil 3D is open, close and restart.
4. Add the new rule to a rule set.
5. The default value looks like it changes to something large after adding it, change it the value that you want, even if you wanted the 80 degree default value.
6. Try it out and see if it works.