A two inch threaded plastic fitting ______________________________.

The appropriate choice indicates that a two-inch threaded plastic fitting may not be used underground. This stems from the Omaha Plumbing Code, which has specific regulations regarding materials and fittings utilized in underground applications. Threaded plastic fittings, particularly those with a diameter of two inches, are generally not permitted for underground installation due to concerns about potential damage, leakage, or improper sealing over time.

Underground installations require fittings that can withstand external pressures and potential ground movement, characteristics that may not be adequately met by threaded fittings. The use of slip fittings, which provide a more secure and leak-proof seal, is typically mandated in these situations. This cautious approach helps ensure the integrity of the plumbing system and complies with safety and performance standards, thus promoting longevity and reliability in plumbing installations.

In contrast to this choice, other options might imply that threaded fittings could be permissible under certain conditions, which does not align with the typical regulations guiding underground plumbing practices within the code.