CWEA Collection Systems Maintenance Grade 2 Exam
Actual 2024 with Detailed Rationales | Complete
Exam-Style Questions | Pass Guaranteed – A+ Graded
SECTION 1: COLLECTION SYSTEM COMPONENTS & OPERATIONS
(Q1–Q14)
Q1: What is the primary function of a force main in a wastewater collection system?
A. To transport wastewater by gravity flow to the treatment plant
B. To provide ventilation for sewer gases
C. To convey wastewater under pressure from a lift station
D. To serve as an emergency overflow during high-flow events
Correct Answer: C
Rationale: Correct because force mains are pressure pipes that convey wastewater
from pump (lift) stations to higher elevations or distant discharge points where
gravity flow cannot be maintained.
Q2: Which component is typically installed at the lowest point of a sewer line to allow
debris and grit to settle for removal?
A. Inverted siphon
B. Manhole
C. Grit chamber or catch basin
D. Air relief valve
Correct Answer: C
Rationale: Correct because grit chambers or catch basins are designed at low points
to intercept heavy solids and grit, preventing abrasion and blockages in downstream
piping.
Q3: A lift station is equipped with submersible pumps. What is the primary
advantage of this design over dry-pit pumps?
A. Lower initial capital cost
B. Easier access for maintenance and repair
C. Elimination of the need for a separate dry well and reduced odor issues
D. Higher energy efficiency at all flow rates
Correct Answer: C
,Rationale: Correct because submersible pumps operate directly in the wet well,
eliminating the need for a separate dry well, reducing construction costs, and
minimizing odor and noise concerns.
Q4: What is the purpose of an inverted siphon in a sewer system?
A. To increase flow velocity through the pipe
B. To carry sewage under an obstruction such as a stream or roadway
C. To ventilate sewer gases to the atmosphere
D. To provide a connection between storm and sanitary sewers
Correct Answer: C
Rationale: Correct because inverted siphons (depressed sewers) are used to carry
wastewater beneath rivers, highways, or other obstacles where a gravity line cannot
be maintained.
Q5: Which material is most commonly used for modern gravity sewer pipe due to its
durability, corrosion resistance, and long service life?
A. Steel
B. Reinforced concrete pipe (RCP) or PVC
C. Cast iron
D. Copper
Correct Answer: C
Rationale: Correct because reinforced concrete pipe (RCP) and polyvinyl chloride
(PVC) are the predominant materials for gravity sewers, offering excellent durability,
chemical resistance, and 50+ year service life.
Q6: What is the typical minimum slope for a 200 mm (8-inch) diameter residential
sewer line to ensure adequate self-cleansing velocity?
A. 0.1%
B. 0.2%
C. 0.4%
D. 1.0%
Correct Answer: C
Rationale: Correct because a minimum slope of approximately 0.4% (0.004 ft/ft) is
standard for 200 mm sewers to maintain a self-cleansing velocity of about 0.6–0.75
m/s (2–2.5 ft/s) during peak flows.
Q7: Which appurtenance is installed on a force main to prevent water hammer and
protect pumps and piping from pressure surges?
, A. Check valve
B. Plug valve
C. Surge relief valve or air/vacuum valve
D. Gate valve
Correct Answer: C
Rationale: Correct because surge relief valves and air/vacuum valves dissipate
pressure waves caused by pump cycling or power failures, preventing water hammer
damage to the force main.
Q8: In a combined sewer system, what is the primary purpose of a regulator or
overflow structure?
A. To increase flow velocity during dry weather
B. To divert excess wet-weather flow to an overflow outfall when capacity is
exceeded
C. To separate stormwater from sanitary flow
D. To inject odor-control chemicals
Correct Answer: C
Rationale: Correct because regulators (CSO structures) are designed to pass
dry-weather and small wet-weather flows to the treatment plant while diverting larger
storm flows to overflow outfalls to prevent system backups.
Q9: What is the primary operational concern when a gravity sewer line is operated at
or near full capacity?
A. Excessive velocity causing pipe erosion
B. Development of negative pressure and collapse
C. Reduced self-cleansing velocity and increased risk of surcharge or basement
backups
D. Freezing of wastewater in the pipe
Correct Answer: C
Rationale: Correct because operating at full capacity eliminates the air space needed
for proper ventilation, reduces scouring velocity, and increases the risk of
surcharging into manholes or building laterals.
Q10: Which type of pump is most commonly used in wastewater lift stations for its
ability to pass solids without clogging?
A. Centrifugal pump with closed impeller
B. Positive displacement piston pump
C. Non-clog centrifugal pump with open or vortex impeller
D. Jet pump
Actual 2024 with Detailed Rationales | Complete
Exam-Style Questions | Pass Guaranteed – A+ Graded
SECTION 1: COLLECTION SYSTEM COMPONENTS & OPERATIONS
(Q1–Q14)
Q1: What is the primary function of a force main in a wastewater collection system?
A. To transport wastewater by gravity flow to the treatment plant
B. To provide ventilation for sewer gases
C. To convey wastewater under pressure from a lift station
D. To serve as an emergency overflow during high-flow events
Correct Answer: C
Rationale: Correct because force mains are pressure pipes that convey wastewater
from pump (lift) stations to higher elevations or distant discharge points where
gravity flow cannot be maintained.
Q2: Which component is typically installed at the lowest point of a sewer line to allow
debris and grit to settle for removal?
A. Inverted siphon
B. Manhole
C. Grit chamber or catch basin
D. Air relief valve
Correct Answer: C
Rationale: Correct because grit chambers or catch basins are designed at low points
to intercept heavy solids and grit, preventing abrasion and blockages in downstream
piping.
Q3: A lift station is equipped with submersible pumps. What is the primary
advantage of this design over dry-pit pumps?
A. Lower initial capital cost
B. Easier access for maintenance and repair
C. Elimination of the need for a separate dry well and reduced odor issues
D. Higher energy efficiency at all flow rates
Correct Answer: C
,Rationale: Correct because submersible pumps operate directly in the wet well,
eliminating the need for a separate dry well, reducing construction costs, and
minimizing odor and noise concerns.
Q4: What is the purpose of an inverted siphon in a sewer system?
A. To increase flow velocity through the pipe
B. To carry sewage under an obstruction such as a stream or roadway
C. To ventilate sewer gases to the atmosphere
D. To provide a connection between storm and sanitary sewers
Correct Answer: C
Rationale: Correct because inverted siphons (depressed sewers) are used to carry
wastewater beneath rivers, highways, or other obstacles where a gravity line cannot
be maintained.
Q5: Which material is most commonly used for modern gravity sewer pipe due to its
durability, corrosion resistance, and long service life?
A. Steel
B. Reinforced concrete pipe (RCP) or PVC
C. Cast iron
D. Copper
Correct Answer: C
Rationale: Correct because reinforced concrete pipe (RCP) and polyvinyl chloride
(PVC) are the predominant materials for gravity sewers, offering excellent durability,
chemical resistance, and 50+ year service life.
Q6: What is the typical minimum slope for a 200 mm (8-inch) diameter residential
sewer line to ensure adequate self-cleansing velocity?
A. 0.1%
B. 0.2%
C. 0.4%
D. 1.0%
Correct Answer: C
Rationale: Correct because a minimum slope of approximately 0.4% (0.004 ft/ft) is
standard for 200 mm sewers to maintain a self-cleansing velocity of about 0.6–0.75
m/s (2–2.5 ft/s) during peak flows.
Q7: Which appurtenance is installed on a force main to prevent water hammer and
protect pumps and piping from pressure surges?
, A. Check valve
B. Plug valve
C. Surge relief valve or air/vacuum valve
D. Gate valve
Correct Answer: C
Rationale: Correct because surge relief valves and air/vacuum valves dissipate
pressure waves caused by pump cycling or power failures, preventing water hammer
damage to the force main.
Q8: In a combined sewer system, what is the primary purpose of a regulator or
overflow structure?
A. To increase flow velocity during dry weather
B. To divert excess wet-weather flow to an overflow outfall when capacity is
exceeded
C. To separate stormwater from sanitary flow
D. To inject odor-control chemicals
Correct Answer: C
Rationale: Correct because regulators (CSO structures) are designed to pass
dry-weather and small wet-weather flows to the treatment plant while diverting larger
storm flows to overflow outfalls to prevent system backups.
Q9: What is the primary operational concern when a gravity sewer line is operated at
or near full capacity?
A. Excessive velocity causing pipe erosion
B. Development of negative pressure and collapse
C. Reduced self-cleansing velocity and increased risk of surcharge or basement
backups
D. Freezing of wastewater in the pipe
Correct Answer: C
Rationale: Correct because operating at full capacity eliminates the air space needed
for proper ventilation, reduces scouring velocity, and increases the risk of
surcharging into manholes or building laterals.
Q10: Which type of pump is most commonly used in wastewater lift stations for its
ability to pass solids without clogging?
A. Centrifugal pump with closed impeller
B. Positive displacement piston pump
C. Non-clog centrifugal pump with open or vortex impeller
D. Jet pump
