Sewer network terminology: Which sewer specifically conveys sewage from the collection system to the treatment works (i.e., unloads at the treatment point)?

Introduction / Context:
Correct terminology prevents design and O&M confusion. The outfall sewer links the collection system to the treatment plant or final disposal location. Knowing this term helps when reading layout drawings and preparing specifications.

Given Data / Assumptions:

• Hierarchical sewer system: house/lateral → branch → main/trunk → outfall.
• Final destination: treatment works.

Concept / Approach:
Outfall sewer is the terminal conduit of the collection system. It carries large combined flows, often with minimal local connections, and is sized for peak wet-weather conditions where applicable. It “unloads” the sewage at the plant headworks.

Step-by-Step Solution:
Identify the last link before the plant.Match term to function: “outfall sewer”.

Verification / Alternative check:
Standard sewer system schematics clearly label the final conduit to the plant as the outfall sewer.

Why Other Options Are Wrong:
Main/branch/lateral/house sewers are upstream collectors with different service areas.

Common Pitfalls:

• Using “main” and “outfall” interchangeably; the outfall is specifically the delivery line to the plant.

Final Answer:
Outfall sewer