Trenches to a new or replaced sewer installation shall remain open until the sewer has been _______.

The appropriate completion for the statement regarding trenches for a new or replaced sewer installation is "Tested, Inspected, and Approved." This comprehensive process ensures that the sewer system is functioning correctly and complies with safety and health standards prior to backfilling the trench.

Testing typically involves checking for leaks, ensuring proper flow and drainage, and verifying that all joints and connections are secure. Inspection allows qualified professionals to examine the installation for conformity to local codes and regulations, while the approval signifies that the installation meets all necessary criteria.

In contrast, the other responses do not encompass the full scope of what is necessary before sealing off a sewer installation. Merely inspecting may overlook issues that testing might reveal, while cleaning or fixing implies a level of completion that isn't applicable before the installation is fully evaluated and sanctioned by regulatory standards. Therefore, the answer reflects the critical steps needed to ensure reliability and safety in sewer installations.