A customer complains of a sewage smell emanating from their rarely used basement floor drain. What is the most probable cause?

Question: A customer complains of a sewage smell emanating from their rarely used basement floor drain. What is the most probable cause?

Answer options:

• A blockage in the main sewer line
• A broken vent pipe ✅ An evaporated trap seal
• A crack in the drain pipe

Correct answer: An evaporated trap seal

Explanation: For a rarely used floor drain, an evaporated trap seal is the most probable cause of a sewage smell. The water in the trap evaporates over time, allowing sewer gases to enter the living space. A blockage would typically cause backups, and a broken vent pipe would affect drainage and create gurgling sounds.