Texas Wastewater Collection System Operator
Class III Exam QUESTIONS AND CORRECT ANSWERS
(VERIFIED ANSWERS) PLUS RATIONALES 2026 Q&A
|INSTANT DOWNLOAD PDF
1. Which of the following is the most common cause of sewer backups
in a collection system?
A. Excessive rainfall
B. Grease buildup
C. Tree root intrusion
D. Mechanical failure
*Correct answer: B. Grease buildup – Grease accumulation is a primary
cause of blockages because it adheres to pipe walls and narrows the
flow, causing backups.
2. What is the primary purpose of a manhole in a wastewater
collection system?
A. To treat wastewater
B. To provide access for inspection and maintenance
C. To store wastewater temporarily
D. To measure flow
*Correct answer: B. To provide access for inspection and maintenance
– Manholes allow operators to inspect, clean, and maintain sewer lines
safely.
3. Which type of pipe is most resistant to corrosion in a wastewater
collection system?
A. PVC
B. Cast iron
,C. Steel
D. Concrete
*Correct answer: A. PVC – PVC is chemically inert, highly resistant to
corrosion, and commonly used in wastewater systems.
4. Hydrogen sulfide (H₂S) in sewers is primarily responsible for:
A. Reducing flow velocity
B. Corroding concrete and metal structures
C. Increasing dissolved oxygen
D. Encouraging microbial growth
*Correct answer: B. Corroding concrete and metal structures – H₂S gas
converts to sulfuric acid when in contact with moisture, corroding pipes.
5. The primary method for preventing grease blockages is:
A. Flushing with hot water
B. Installing grease traps
C. Regularly flushing with chlorine
D. Reducing pipe slope
*Correct answer: B. Installing grease traps – Grease traps capture fats,
oils, and grease before they enter the sewer system.
6. What is the minimum slope for a 6-inch diameter sewer pipe to
maintain self-cleansing velocity?
A. 0.5%
B. 1%
C. 2%
D. 4%
*Correct answer: B. 1% – A 1% slope ensures adequate flow velocity to
prevent solids from settling in the pipe.
7. Which type of lift station pump is commonly used in Class III
systems?
A. Submersible centrifugal pump
, B. Positive displacement pump
C. Reciprocating pump
D. Diaphragm pump
*Correct answer: A. Submersible centrifugal pump – These pumps are
efficient, durable, and widely used in wastewater lift stations.
8. The best method to detect leaks in a sewer main is:
A. Smoke testing
B. Visual inspection from the surface
C. Manual digging along the pipe
D. Measuring flow at treatment plant
*Correct answer: A. Smoke testing – Smoke testing introduces non-toxic
smoke into the system to identify leaks and illegal connections.
9. What is the main purpose of a sewer flushing program?
A. To disinfect wastewater
B. To remove accumulated solids and debris
C. To test pipe strength
D. To increase H₂S production
*Correct answer: B. To remove accumulated solids and debris – Regular
flushing prevents blockages and maintains pipe flow.
10. In wastewater collection, what is the primary concern when sewer
gas accumulates in confined spaces?
A. Reduced microbial activity
B. Fire and explosion hazard
C. Increased flow velocity
D. Corrosion of PVC pipes
*Correct answer: B. Fire and explosion hazard – Methane and H₂S gases
can be explosive and pose serious safety risks.
11. Roots from nearby trees enter sewer lines primarily through:
A. Joints and cracks
Class III Exam QUESTIONS AND CORRECT ANSWERS
(VERIFIED ANSWERS) PLUS RATIONALES 2026 Q&A
|INSTANT DOWNLOAD PDF
1. Which of the following is the most common cause of sewer backups
in a collection system?
A. Excessive rainfall
B. Grease buildup
C. Tree root intrusion
D. Mechanical failure
*Correct answer: B. Grease buildup – Grease accumulation is a primary
cause of blockages because it adheres to pipe walls and narrows the
flow, causing backups.
2. What is the primary purpose of a manhole in a wastewater
collection system?
A. To treat wastewater
B. To provide access for inspection and maintenance
C. To store wastewater temporarily
D. To measure flow
*Correct answer: B. To provide access for inspection and maintenance
– Manholes allow operators to inspect, clean, and maintain sewer lines
safely.
3. Which type of pipe is most resistant to corrosion in a wastewater
collection system?
A. PVC
B. Cast iron
,C. Steel
D. Concrete
*Correct answer: A. PVC – PVC is chemically inert, highly resistant to
corrosion, and commonly used in wastewater systems.
4. Hydrogen sulfide (H₂S) in sewers is primarily responsible for:
A. Reducing flow velocity
B. Corroding concrete and metal structures
C. Increasing dissolved oxygen
D. Encouraging microbial growth
*Correct answer: B. Corroding concrete and metal structures – H₂S gas
converts to sulfuric acid when in contact with moisture, corroding pipes.
5. The primary method for preventing grease blockages is:
A. Flushing with hot water
B. Installing grease traps
C. Regularly flushing with chlorine
D. Reducing pipe slope
*Correct answer: B. Installing grease traps – Grease traps capture fats,
oils, and grease before they enter the sewer system.
6. What is the minimum slope for a 6-inch diameter sewer pipe to
maintain self-cleansing velocity?
A. 0.5%
B. 1%
C. 2%
D. 4%
*Correct answer: B. 1% – A 1% slope ensures adequate flow velocity to
prevent solids from settling in the pipe.
7. Which type of lift station pump is commonly used in Class III
systems?
A. Submersible centrifugal pump
, B. Positive displacement pump
C. Reciprocating pump
D. Diaphragm pump
*Correct answer: A. Submersible centrifugal pump – These pumps are
efficient, durable, and widely used in wastewater lift stations.
8. The best method to detect leaks in a sewer main is:
A. Smoke testing
B. Visual inspection from the surface
C. Manual digging along the pipe
D. Measuring flow at treatment plant
*Correct answer: A. Smoke testing – Smoke testing introduces non-toxic
smoke into the system to identify leaks and illegal connections.
9. What is the main purpose of a sewer flushing program?
A. To disinfect wastewater
B. To remove accumulated solids and debris
C. To test pipe strength
D. To increase H₂S production
*Correct answer: B. To remove accumulated solids and debris – Regular
flushing prevents blockages and maintains pipe flow.
10. In wastewater collection, what is the primary concern when sewer
gas accumulates in confined spaces?
A. Reduced microbial activity
B. Fire and explosion hazard
C. Increased flow velocity
D. Corrosion of PVC pipes
*Correct answer: B. Fire and explosion hazard – Methane and H₂S gases
can be explosive and pose serious safety risks.
11. Roots from nearby trees enter sewer lines primarily through:
A. Joints and cracks
