TCEQ Class C Water License Examination 2026–
2027 | Comprehensive 150 -Question Practice
Test with Answers & Rationales| Free Pdf Access
Question 1
What is the primary state agency responsible for enforcing the Safe Drinking Water Act
(SDWA) in Texas?
A) Texas Department of State Health Services
B) Texas Water Development Board
C) Texas Commission on Environmental Quality (TCEQ)
D) Environmental Protection Agency (EPA)
Correct Answer: C
The Texas Commission on Environmental Quality (TCEQ) is the primary state agency
responsible for implementing and enforcing the Safe Drinking Water Act within Texas.
While the EPA sets the national standards, TCEQ is the delegated authority that enforces
them at the state level .
Question 2
What is the maximum contaminant level (MCL) for total coliform bacteria in a public
water system that collects 40 or more samples per month?
A) No more than 1 sample positive per month
B) No more than 5% of samples positive per month
C) 0% positive samples
D) No more than 10% positive samples
Correct Answer: B
Under the Revised Total Coliform Rule (RTCR), systems collecting 40 or more samples per
month must have no more than 5% of their samples test positive for total coliform.
Systems collecting fewer than 40 samples are allowed no more than one positive sample
,per month. The exam often emphasizes the stricter "zero tolerance" expectation for routine
compliance, making B the correct choice .
Question 3
A water sample tests positive for E. coli. What is the required action?
A) Collect a repeat sample within 24 hours
B) Issue a boil water notice within 24 hours
C) Collect 3 repeat samples within 24 hours and notify TCEQ within 24 hours
D) Nothing, unless two consecutive positives occur
Correct Answer: C
An E. coli positive is considered an acute violation and requires immediate action. The
system must collect 3 repeat samples (one at the original site, one upstream, and one
downstream) and notify TCEQ within 24 hours. A boil water notice must also be issued to
the public .
Question 4
What is the maximum turbidity level allowed for an individual filter effluent at any time
in a conventional treatment plant?
A) 0.3 NTU
B) 0.5 NTU
C) 1.0 NTU
D) 5.0 NTU
Correct Answer: C
For systems using conventional or direct filtration, the maximum turbidity for an
individual filter at any time is 1.0 NTU. The monthly compliance limit is that at least 95%
of the samples must be at or below 0.3 NTU .
Question 5
What is the minimum required free chlorine residual that must be maintained
throughout the distribution system at all times?
A) 0.2 mg/L
B) 0.5 mg/L
C) 1.0 mg/L
D) 0.1 mg/L
Correct Answer: A
,TCEQ rules (30 TAC 290.113) require a free chlorine residual of at least 0.2 mg/L
throughout the distribution system at all times. If the system uses chloramines, the total
chlorine residual must be at least 0.5 mg/L .
Question 6
What is the action level for lead in drinking water based on the 90th percentile of tap
samples?
A) 0.015 mg/L
B) 0.005 mg/L
C) 0.10 mg/L
D) 0.001 mg/L
Correct Answer: A
The action level for lead under the Lead and Copper Rule is 0.015 mg/L (15 parts per
billion). If the 90th percentile of samples exceeds this level, the system must take
additional actions such as corrosion control treatment and public education .
Question 7
What is the minimum operating pressure required in a distribution system under normal
conditions?
A) 20 psi
B) 35 psi
C) 50 psi
D) 60 psi
Correct Answer: B
TCEQ rules require that water distribution systems maintain a minimum pressure of 35 psi
under normal operating conditions and must not fall below 20 psi during emergencies.
Maintaining proper pressure helps prevent backflow and contamination .
Question 8
What is the pH scale range?
A) 1 to 10
B) 0 to 14
C) 5 to 15
D) 2 to 12
Correct Answer: B
, The pH scale ranges from 0 to 14. A pH of 7 is neutral; below 7 is acidic, and above 7 is
basic (alkaline). Water with a pH below 6.5 is considered acidic .
Question 9
What is the primary purpose of coagulation in the surface water treatment process?
A) To kill bacteria and viruses
B) To neutralize the electrical charges of suspended particles so they can clump together
C) To filter out large debris
D) To add fluoride to the water
Correct Answer: B
Coagulation is the process of adding chemicals to raw water to neutralize the electrical
charges of suspended particles. This allows the particles to clump together into larger
masses called floc, which can then be removed during sedimentation and filtration .
Question 10
What is drawdown in a well?
A) The total depth of the well
B) The amount of water a well produces per minute
C) The difference between the static water level and the pumping water level
D) The pressure at the bottom of the well
Correct Answer: C
Drawdown is the drop in the water level in a well that occurs when it is pumped. It is
calculated as the difference between the static water level (when the well is not pumping)
and the pumping water level (when the well is pumping) .
Question 11
What is the most common type of pump used in water distribution systems?
A) Positive displacement pump
B) Centrifugal pump
C) Turbine pump
D) Airlift pump
Correct Answer: B
2027 | Comprehensive 150 -Question Practice
Test with Answers & Rationales| Free Pdf Access
Question 1
What is the primary state agency responsible for enforcing the Safe Drinking Water Act
(SDWA) in Texas?
A) Texas Department of State Health Services
B) Texas Water Development Board
C) Texas Commission on Environmental Quality (TCEQ)
D) Environmental Protection Agency (EPA)
Correct Answer: C
The Texas Commission on Environmental Quality (TCEQ) is the primary state agency
responsible for implementing and enforcing the Safe Drinking Water Act within Texas.
While the EPA sets the national standards, TCEQ is the delegated authority that enforces
them at the state level .
Question 2
What is the maximum contaminant level (MCL) for total coliform bacteria in a public
water system that collects 40 or more samples per month?
A) No more than 1 sample positive per month
B) No more than 5% of samples positive per month
C) 0% positive samples
D) No more than 10% positive samples
Correct Answer: B
Under the Revised Total Coliform Rule (RTCR), systems collecting 40 or more samples per
month must have no more than 5% of their samples test positive for total coliform.
Systems collecting fewer than 40 samples are allowed no more than one positive sample
,per month. The exam often emphasizes the stricter "zero tolerance" expectation for routine
compliance, making B the correct choice .
Question 3
A water sample tests positive for E. coli. What is the required action?
A) Collect a repeat sample within 24 hours
B) Issue a boil water notice within 24 hours
C) Collect 3 repeat samples within 24 hours and notify TCEQ within 24 hours
D) Nothing, unless two consecutive positives occur
Correct Answer: C
An E. coli positive is considered an acute violation and requires immediate action. The
system must collect 3 repeat samples (one at the original site, one upstream, and one
downstream) and notify TCEQ within 24 hours. A boil water notice must also be issued to
the public .
Question 4
What is the maximum turbidity level allowed for an individual filter effluent at any time
in a conventional treatment plant?
A) 0.3 NTU
B) 0.5 NTU
C) 1.0 NTU
D) 5.0 NTU
Correct Answer: C
For systems using conventional or direct filtration, the maximum turbidity for an
individual filter at any time is 1.0 NTU. The monthly compliance limit is that at least 95%
of the samples must be at or below 0.3 NTU .
Question 5
What is the minimum required free chlorine residual that must be maintained
throughout the distribution system at all times?
A) 0.2 mg/L
B) 0.5 mg/L
C) 1.0 mg/L
D) 0.1 mg/L
Correct Answer: A
,TCEQ rules (30 TAC 290.113) require a free chlorine residual of at least 0.2 mg/L
throughout the distribution system at all times. If the system uses chloramines, the total
chlorine residual must be at least 0.5 mg/L .
Question 6
What is the action level for lead in drinking water based on the 90th percentile of tap
samples?
A) 0.015 mg/L
B) 0.005 mg/L
C) 0.10 mg/L
D) 0.001 mg/L
Correct Answer: A
The action level for lead under the Lead and Copper Rule is 0.015 mg/L (15 parts per
billion). If the 90th percentile of samples exceeds this level, the system must take
additional actions such as corrosion control treatment and public education .
Question 7
What is the minimum operating pressure required in a distribution system under normal
conditions?
A) 20 psi
B) 35 psi
C) 50 psi
D) 60 psi
Correct Answer: B
TCEQ rules require that water distribution systems maintain a minimum pressure of 35 psi
under normal operating conditions and must not fall below 20 psi during emergencies.
Maintaining proper pressure helps prevent backflow and contamination .
Question 8
What is the pH scale range?
A) 1 to 10
B) 0 to 14
C) 5 to 15
D) 2 to 12
Correct Answer: B
, The pH scale ranges from 0 to 14. A pH of 7 is neutral; below 7 is acidic, and above 7 is
basic (alkaline). Water with a pH below 6.5 is considered acidic .
Question 9
What is the primary purpose of coagulation in the surface water treatment process?
A) To kill bacteria and viruses
B) To neutralize the electrical charges of suspended particles so they can clump together
C) To filter out large debris
D) To add fluoride to the water
Correct Answer: B
Coagulation is the process of adding chemicals to raw water to neutralize the electrical
charges of suspended particles. This allows the particles to clump together into larger
masses called floc, which can then be removed during sedimentation and filtration .
Question 10
What is drawdown in a well?
A) The total depth of the well
B) The amount of water a well produces per minute
C) The difference between the static water level and the pumping water level
D) The pressure at the bottom of the well
Correct Answer: C
Drawdown is the drop in the water level in a well that occurs when it is pumped. It is
calculated as the difference between the static water level (when the well is not pumping)
and the pumping water level (when the well is pumping) .
Question 11
What is the most common type of pump used in water distribution systems?
A) Positive displacement pump
B) Centrifugal pump
C) Turbine pump
D) Airlift pump
Correct Answer: B
