Texas Class D Water License Exam Study Guide |
Complete Question Bank with Verified Correct Answers
and Detailed Rationales (100% Correct Solutions) |
Latest 2026/2027 Update – Already Graded A+
Question 1
Trenches for laying six-inch and larger pipe must be at least ___ inches wide and ___
inches wider than the pipe diameter.
A. 12 inches wide, 6 inches wider
B. 18 inches wide, 12 inches wider
C. 24 inches wide, 18 inches wider
D. 30 inches wide, 24 inches wider
Answer: B
Rationale: Trenches must be at least 18 inches wide and 12 inches wider than the pipe
diameter for proper installation and working space.
Question 2
A federal agency impacting the water utility industry is the:
A. FDA
B. EPA
C. USDA
D. DOE
Answer: B
Rationale: The Environmental Protection Agency (EPA) is the primary federal agency
that regulates drinking water quality and the water utility industry.
Question 3
Meter readers can be ambassadors of goodwill. (True/False)
Answer: True
Rationale: Meter readers are often the only utility employees customers interact with,
and they represent the utility's public image.
pg. 1
,Question 4
A system's filtered water must be __ Nephelometric Turbidity Units (NTU) or less in at
least __% of measurements taken each month, and no sample can exceed __ NTU.
A. 0.5 NTUs, 80%, 2 NTUs
B. 0.2 NTUs, 90%, 0.8 NTUs
C. 0.3 NTUs, 95%, 1 NTU
D. 0.4 NTUs, 75%, 1.5 NTUs
Answer: C
Rationale: Filtered water must be 0.3 NTU or less in at least 95% of measurements,
with no sample exceeding 1 NTU.
Question 5
_______ is a buildup of oxidized iron, calcium carbonate, or other chemicals in mains.
A. Sedimentation
B. Oxidation
C. Tuberculation
D. Mineralization
Answer: C
Rationale: Tuberculation is the buildup of oxidized iron, calcium carbonate, and other
deposits inside water mains, which reduces flow capacity.
Question 6
The TCEQ requires that distribution pressure never fall below ___ psi, even during
emergencies, and normal distribution pressure must be at least ___ psi.
A. Courteous treatment and answers to questions about water
B. Never fall below 20 psi; 35 psi (normal distribution)
C. False (meter readers often have the most contact)
D. False (only fill 100 ml unless the lab tells you otherwise)
Answer: B
Rationale: Distribution pressure must never fall below 20 psi even during
emergencies, and normal operating pressure must be at least 35 psi.
Question 7
Calcium hypochlorite is not dry chlorine. Dry chlorine is pure chlorine, liquid or gas,
containing less than ___ ppm water.
A. 200 ppm
B. 50 ppm
C. 100 ppm
pg. 2
,D. 150 ppm
Answer: D
Rationale: Dry chlorine contains less than 150 ppm water, whereas calcium
hypochlorite contains water and is not considered "dry chlorine."
Question 8
One bacteriological sample is required for each ___ feet of completed main.
A. 2,000 feet
B. 1,000 feet
C. 500 feet
D. 1,500 feet
Answer: B
Rationale: One bacteriological sample is required for each 1,000 feet of completed
main.
Question 9
Boat ramps, marinas, and docks should not be located within ___ feet of a water intake.
A. 1,500 feet
B. 1,000 feet
C. 250 feet
D. 500 feet
Answer: D
Rationale: Intakes must be at least 500 feet away from boat ramps, marinas, and
docks to prevent contamination.
Question 10
The four national safety and quality standards for drinking water covered in the Safe
Drinking Water Act are physical, chemical, ___ and radiological.
A. bacteriological
B. electrical
C. thermal
D. mechanical
Answer: A
Rationale: The four categories are physical, chemical, bacteriological, and radiological
standards.
pg. 3
, Question 11
Dosage is the amount of chemical applied, demand is the amount of chemical used up,
and ___ is the amount remaining after reacting with demand.
A. absorption
B. residual
C. efficiency
D. concentration
Answer: B
Rationale: Residual is the amount of chemical remaining after the demand has been
satisfied.
Question 12
The DPD and chlorine reaction turns the water a ______ color.
A. purple to violet
B. blue to green
C. pink to red
D. yellow to orange
Answer: C
Rationale: DPD indicator turns pink to red in the presence of chlorine.
Question 13
Mains must be no closer than ___ feet, in all directions, from sewers or manholes.
A. 12 feet
B. 6 feet
C. 9 feet
D. 3 feet
Answer: C
Rationale: Mains must be at least 9 feet from sewers or manholes to prevent
contamination.
Question 14
The most common pump in the water utility field is the ______ pump.
A. Centrifugal pump
B. Axial flow pump
C. Rotary vane pump
D. Submersible pump
Answer: A
Rationale: Centrifugal pumps are the most common type used in water distribution.
pg. 4
Complete Question Bank with Verified Correct Answers
and Detailed Rationales (100% Correct Solutions) |
Latest 2026/2027 Update – Already Graded A+
Question 1
Trenches for laying six-inch and larger pipe must be at least ___ inches wide and ___
inches wider than the pipe diameter.
A. 12 inches wide, 6 inches wider
B. 18 inches wide, 12 inches wider
C. 24 inches wide, 18 inches wider
D. 30 inches wide, 24 inches wider
Answer: B
Rationale: Trenches must be at least 18 inches wide and 12 inches wider than the pipe
diameter for proper installation and working space.
Question 2
A federal agency impacting the water utility industry is the:
A. FDA
B. EPA
C. USDA
D. DOE
Answer: B
Rationale: The Environmental Protection Agency (EPA) is the primary federal agency
that regulates drinking water quality and the water utility industry.
Question 3
Meter readers can be ambassadors of goodwill. (True/False)
Answer: True
Rationale: Meter readers are often the only utility employees customers interact with,
and they represent the utility's public image.
pg. 1
,Question 4
A system's filtered water must be __ Nephelometric Turbidity Units (NTU) or less in at
least __% of measurements taken each month, and no sample can exceed __ NTU.
A. 0.5 NTUs, 80%, 2 NTUs
B. 0.2 NTUs, 90%, 0.8 NTUs
C. 0.3 NTUs, 95%, 1 NTU
D. 0.4 NTUs, 75%, 1.5 NTUs
Answer: C
Rationale: Filtered water must be 0.3 NTU or less in at least 95% of measurements,
with no sample exceeding 1 NTU.
Question 5
_______ is a buildup of oxidized iron, calcium carbonate, or other chemicals in mains.
A. Sedimentation
B. Oxidation
C. Tuberculation
D. Mineralization
Answer: C
Rationale: Tuberculation is the buildup of oxidized iron, calcium carbonate, and other
deposits inside water mains, which reduces flow capacity.
Question 6
The TCEQ requires that distribution pressure never fall below ___ psi, even during
emergencies, and normal distribution pressure must be at least ___ psi.
A. Courteous treatment and answers to questions about water
B. Never fall below 20 psi; 35 psi (normal distribution)
C. False (meter readers often have the most contact)
D. False (only fill 100 ml unless the lab tells you otherwise)
Answer: B
Rationale: Distribution pressure must never fall below 20 psi even during
emergencies, and normal operating pressure must be at least 35 psi.
Question 7
Calcium hypochlorite is not dry chlorine. Dry chlorine is pure chlorine, liquid or gas,
containing less than ___ ppm water.
A. 200 ppm
B. 50 ppm
C. 100 ppm
pg. 2
,D. 150 ppm
Answer: D
Rationale: Dry chlorine contains less than 150 ppm water, whereas calcium
hypochlorite contains water and is not considered "dry chlorine."
Question 8
One bacteriological sample is required for each ___ feet of completed main.
A. 2,000 feet
B. 1,000 feet
C. 500 feet
D. 1,500 feet
Answer: B
Rationale: One bacteriological sample is required for each 1,000 feet of completed
main.
Question 9
Boat ramps, marinas, and docks should not be located within ___ feet of a water intake.
A. 1,500 feet
B. 1,000 feet
C. 250 feet
D. 500 feet
Answer: D
Rationale: Intakes must be at least 500 feet away from boat ramps, marinas, and
docks to prevent contamination.
Question 10
The four national safety and quality standards for drinking water covered in the Safe
Drinking Water Act are physical, chemical, ___ and radiological.
A. bacteriological
B. electrical
C. thermal
D. mechanical
Answer: A
Rationale: The four categories are physical, chemical, bacteriological, and radiological
standards.
pg. 3
, Question 11
Dosage is the amount of chemical applied, demand is the amount of chemical used up,
and ___ is the amount remaining after reacting with demand.
A. absorption
B. residual
C. efficiency
D. concentration
Answer: B
Rationale: Residual is the amount of chemical remaining after the demand has been
satisfied.
Question 12
The DPD and chlorine reaction turns the water a ______ color.
A. purple to violet
B. blue to green
C. pink to red
D. yellow to orange
Answer: C
Rationale: DPD indicator turns pink to red in the presence of chlorine.
Question 13
Mains must be no closer than ___ feet, in all directions, from sewers or manholes.
A. 12 feet
B. 6 feet
C. 9 feet
D. 3 feet
Answer: C
Rationale: Mains must be at least 9 feet from sewers or manholes to prevent
contamination.
Question 14
The most common pump in the water utility field is the ______ pump.
A. Centrifugal pump
B. Axial flow pump
C. Rotary vane pump
D. Submersible pump
Answer: A
Rationale: Centrifugal pumps are the most common type used in water distribution.
pg. 4
