Sewer maintenance methods: Which statements about cleaning small, medium, and large sewers are correct?

Introduction / Context:
Sewer operation and maintenance requires different methods depending on pipe size, access, and nature of deposits. Proper technique selection maintains hydraulic capacity, prevents blockages, and protects public health.

Given Data / Assumptions:

• “Small”, “medium”, and “large” refer to typical municipal diameters.
• Deposits include grit, grease, roots, and organic solids.
• Access via manholes is available.

Concept / Approach:

Small sewers are often flushed using water jets or periodic surges. Medium sewers can be cleared using cane rodding or wooden pills (also called cleaning balls or pigs) that push or entrain deposits. Large sewers typically require entry or remote equipment to remove deposits using buckets, jetting trucks, or mechanical scrapers.

Step-by-Step Solution:

Verification / Alternative check:

Utility SOPs and O&M manuals align with this tiered approach, adding modern tools like high-pressure jetting and CCTV inspections.

Why Other Options Are Wrong:

Options (a) to (d) are each correct individually; the best consolidated choice is (e) “All of the above”.

Common Pitfalls:

Using excessive flushing where surcharge risk exists; rodding fragile pipes; entering large sewers without proper confined-space procedures.

Final Answer:

All of the above