A short note on splitting pipes. This pretty standard functionality in the Revit MEP user interface can be a bit tricky to find in the API:
Question: The UI provides the split command (SL) to split a pipe into two without losing other connected elements. How can I achieve the same in API?
Answer: You can use the PlumbingUtils BreakCurve method.
This is also available for duct work in MechanicalUtils BreakCurve.