Final answer:
Plumbing systems that require a permit are inspected by the local authority having jurisdiction (AHJ).
Step-by-step explanation:
In the context of building codes, plumbing systems that require a permit are inspected by the local authority having jurisdiction (AHJ). This could be the building department or the plumbing inspector, depending on the specific regulations of the area. The AHJ ensures that the plumbing system meets the standards set forth in the code and is safe for use.