After the conduit is installed in a trench and been backfilled, but before any surface construction begins, it is common practice to check duct quality because certain plastic conduits can become oval-shaped, pierced or broken. This Recommendation describes inspection methods such as test mandrel and CCTV system to check duct quality, and also describes various methods that are utilized to repair underground conduits. Repairing methods without digging, called "trenchless techniques," are introduced and traditional repairing methods (dig and replace) is also presented. Additionally, guideline for selecting an appropriate repairing method is proposed. It is expected that this Recommendation will provide alternative solutions for inspecting and repairing work.