CWEA COLLECTIONS SYSTEM MAINTENANCE
GRADE 3 PRACTICE EXAM QUESTIONS AND
CORRECT DETAILED ANSWERS LATEST
UPDATES 2026-2027 (VERIFIED ANSWERS)
ALREADY GRADED A+
This study guide contains 100 advanced CWEA Collections System Maintenance Grade 3 practice questions
designed to simulate the difficulty of the real certification exam. Each question includes multiple-choice answers,
clearly highlighted correct responses, and detailed explanations to help you understand key wastewater collection
system concepts such as sewer maintenance, lift stations, infiltration and inflow, gas safety, inspection techniques, and
preventive maintenance strategies.
Use this resource to test your knowledge, identify weak areas, and build confidence before taking the CWEA
Grade 3 exam.
1.
A sewer cleaning crew uses a combination jet/vac truck to remove heavy grease from a line. What is the
primary purpose of the high-pressure jetting nozzle?
A. Pump sewage to a treatment plant
B. Break up and flush debris toward the manhole
C. Measure sewer flow
D. Seal the pipe interior
Rationale: Jetting nozzles use high-pressure water to dislodge debris and push it downstream toward the
vacuum hose for removal.
2.
Which gas is most commonly responsible for the “rotten egg” odor in sewer systems?
A. Carbon dioxide
B. Methane
,C. Hydrogen sulfide
D. Nitrogen
Rationale: Hydrogen sulfide (H₂S) is produced by anaerobic bacteria and has a characteristic rotten egg smell.
3.
A confined space entry into a sewer requires atmospheric testing. Which gas should be tested first?
A. Hydrogen sulfide
B. Carbon monoxide
C. Methane
D. Oxygen
Rationale: Oxygen concentration must be checked first to ensure the environment can support life before
testing for toxic gases.
4.
Which device is most commonly used to measure wastewater flow in a partially full sewer pipe?
A. Pitot tube
B. Parshall flume
C. Hydrometer
D. Thermometer
Rationale: Parshall flumes measure open channel flow using water depth and channel geometry.
5.
A sewer line that flows without pumps using gravity is called:
A. Force main
B. Lift line
C. Gravity sewer
D. Pressure conduit
Rationale: Gravity sewers rely on pipe slope to move wastewater naturally.
, 6.
What is the primary purpose of a lift station?
A. Filter wastewater
B. Measure sewer gases
C. Pump wastewater from a lower to a higher elevation
D. Remove grease
Rationale: Lift stations move wastewater when gravity flow is not possible.
7.
Which condition most commonly causes sanitary sewer overflows (SSOs)?
A. Low pipe slope
B. Blockages or capacity overloads
C. High oxygen levels
D. Chlorine injection
Rationale: SSOs are often caused by blockages from grease, roots, or debris.
8.
Tree roots most commonly enter sewer pipes through:
A. Pipe walls
B. Pipe center
C. Pipe joints or cracks
D. Manhole covers
Rationale: Roots infiltrate through small openings where moisture and nutrients are present.
9.
Which tool is commonly used to cut tree roots in sewer lines?
GRADE 3 PRACTICE EXAM QUESTIONS AND
CORRECT DETAILED ANSWERS LATEST
UPDATES 2026-2027 (VERIFIED ANSWERS)
ALREADY GRADED A+
This study guide contains 100 advanced CWEA Collections System Maintenance Grade 3 practice questions
designed to simulate the difficulty of the real certification exam. Each question includes multiple-choice answers,
clearly highlighted correct responses, and detailed explanations to help you understand key wastewater collection
system concepts such as sewer maintenance, lift stations, infiltration and inflow, gas safety, inspection techniques, and
preventive maintenance strategies.
Use this resource to test your knowledge, identify weak areas, and build confidence before taking the CWEA
Grade 3 exam.
1.
A sewer cleaning crew uses a combination jet/vac truck to remove heavy grease from a line. What is the
primary purpose of the high-pressure jetting nozzle?
A. Pump sewage to a treatment plant
B. Break up and flush debris toward the manhole
C. Measure sewer flow
D. Seal the pipe interior
Rationale: Jetting nozzles use high-pressure water to dislodge debris and push it downstream toward the
vacuum hose for removal.
2.
Which gas is most commonly responsible for the “rotten egg” odor in sewer systems?
A. Carbon dioxide
B. Methane
,C. Hydrogen sulfide
D. Nitrogen
Rationale: Hydrogen sulfide (H₂S) is produced by anaerobic bacteria and has a characteristic rotten egg smell.
3.
A confined space entry into a sewer requires atmospheric testing. Which gas should be tested first?
A. Hydrogen sulfide
B. Carbon monoxide
C. Methane
D. Oxygen
Rationale: Oxygen concentration must be checked first to ensure the environment can support life before
testing for toxic gases.
4.
Which device is most commonly used to measure wastewater flow in a partially full sewer pipe?
A. Pitot tube
B. Parshall flume
C. Hydrometer
D. Thermometer
Rationale: Parshall flumes measure open channel flow using water depth and channel geometry.
5.
A sewer line that flows without pumps using gravity is called:
A. Force main
B. Lift line
C. Gravity sewer
D. Pressure conduit
Rationale: Gravity sewers rely on pipe slope to move wastewater naturally.
, 6.
What is the primary purpose of a lift station?
A. Filter wastewater
B. Measure sewer gases
C. Pump wastewater from a lower to a higher elevation
D. Remove grease
Rationale: Lift stations move wastewater when gravity flow is not possible.
7.
Which condition most commonly causes sanitary sewer overflows (SSOs)?
A. Low pipe slope
B. Blockages or capacity overloads
C. High oxygen levels
D. Chlorine injection
Rationale: SSOs are often caused by blockages from grease, roots, or debris.
8.
Tree roots most commonly enter sewer pipes through:
A. Pipe walls
B. Pipe center
C. Pipe joints or cracks
D. Manhole covers
Rationale: Roots infiltrate through small openings where moisture and nutrients are present.
9.
Which tool is commonly used to cut tree roots in sewer lines?
