Sewer appurtenances: Identify the incorrect statement regarding manholes, catch basins, and inlets in sewer systems.
-
AManholes are provided in sewer lines at suitable intervals for access and maintenance
-
BCatch basins are generally provided to intercept street drainage and prevent debris entering sewers
-
CInlets are generally provided in all sewers regardless of type and location
-
DNone of these
-
EManholes allow change of direction, grade, or junctions in sewers
Answer
Correct Answer: Inlets are generally provided in all sewers regardless of type and location
Explanation
Introduction / Context:
Sewer networks include several appurtenances—manholes for access, catch basins and inlets for street drainage interception. Understanding their correct placement helps ensure functionality and ease of maintenance.
Given Data / Assumptions:
- Combined versus separate sewer systems have different inlet strategies.
- Manholes are routine access points.
- Catch basins separate grit/debris from roadway runoff before entering storm sewers.
Concept / Approach:
It is incorrect to claim that inlets are provided in all sewers. Inlets are features of stormwater collection along curbs and streets; they are not required on sanitary-only sewers that receive flows from building laterals rather than street runoff.
Step-by-Step Solution:
Confirm manhole usage: access, alignment changes, and junctions.Note catch basins: first-line debris traps in storm systems.Identify the incorrect universal statement about inlets across all sewer types.Verification / Alternative check:
Separate sanitary systems have no street inlets by design; thus the statement claiming universality is false.
Why Other Options Are Wrong:
- Manhole statements are true and standard practice.
- None of these is wrong because one statement is indeed incorrect.
Common Pitfalls:
- Confusing combined systems (which may have inlets) with sanitary-only systems.
Final Answer:
Inlets are generally provided in all sewers regardless of type and location