TCEQ Class C Water License Exam | Complete
Study Guides with Actual Exam Questions,
Verified Correct Answers and Detailed Rationales
| Latest Update 2026/2027
1. What is the primary purpose of a Class C water license in Texas?
A) To certify operators managing wastewater systems only
B) To allow operators to sell water treatment chemicals
C) To certify operators of small to medium public water systems
D) To license engineers designing water treatment plants
Answer C: To certify operators of small to medium public water systems
Rationale: The TCEQ Class C Water Operator License certifies individuals who
operate small to medium-sized public water supply systems in Texas .
2. Which federal law is the primary legislation governing public drinking
water safety in the United States?
A) Clean Water Act (CWA)
B) Resource Conservation and Recovery Act (RCRA)
C) Safe Drinking Water Act (SDWA)
D) National Environmental Policy Act (NEPA)
Answer C: Safe Drinking Water Act (SDWA)
,Rationale: The Safe Drinking Water Act (SDWA), enacted in 1974, is the primary
federal law that protects public drinking water supplies throughout the United
States .
3. What does MCL stand for in water quality regulations?
A) Maximum Contaminant Limit
B) Maximum Contaminant Level
C) Minimum Chlorine Limit
D) Mandatory Compliance Level
Answer B: Maximum Contaminant Level
Rationale: MCL stands for Maximum Contaminant Level, which is the highest
permissible level of a contaminant in drinking water. MCLs are enforceable
standards set by the EPA .
4. What is the MCLG for total coliforms in drinking water?
A) 1 CFU/100 mL
B) 5% positive samples per month
C) Zero
D) 0.5 CFU/100 mL
Answer C: Zero
Rationale: The Maximum Contaminant Level Goal (MCLG) for total coliforms is
zero because any coliform bacteria in drinking water may pose a health risk and
indicates possible contamination .
,5. Which of the following is a surface water source?
A) Artesian well
B) Confined aquifer
C) River
D) Water table well
Answer C: River
Rationale: Rivers are surface water sources. Surface water includes rivers, lakes,
reservoirs, and streams. Groundwater sources include wells and springs fed by
aquifers .
6. What is turbidity a measure of in water?
A) Bacterial count
B) Chemical oxygen demand
C) Cloudiness or haziness caused by suspended particles
D) Dissolved oxygen concentration
Answer C: Cloudiness or haziness caused by suspended particles
Rationale: Turbidity is a measure of water clarity. It reflects how much light is
scattered by suspended particles. High turbidity can interfere with disinfection .
7. What unit is turbidity measured in?
A) mg/L
, B) ppm
C) NTU (Nephelometric Turbidity Units)
D) JTU
Answer C: NTU (Nephelometric Turbidity Units)
Rationale: Turbidity is measured in Nephelometric Turbidity Units (NTU) using a
nephelometer, which measures light scattered at 90 degrees by suspended
particles .
8. The maximum turbidity allowed in treated drinking water leaving a
conventional filtration plant is:
A) 0.3 NTU for 95% of samples in a month
B) 0.5 NTU
C) 1.0 NTU
D) 5.0 NTU
Answer A: 0.3 NTU for 95% of samples in a month
Rationale: Conventional filtration plants must achieve turbidity ≤0.3 NTU in at
least 95% of monthly samples .
9. 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
D) Nothing unless two consecutive positives occur
Study Guides with Actual Exam Questions,
Verified Correct Answers and Detailed Rationales
| Latest Update 2026/2027
1. What is the primary purpose of a Class C water license in Texas?
A) To certify operators managing wastewater systems only
B) To allow operators to sell water treatment chemicals
C) To certify operators of small to medium public water systems
D) To license engineers designing water treatment plants
Answer C: To certify operators of small to medium public water systems
Rationale: The TCEQ Class C Water Operator License certifies individuals who
operate small to medium-sized public water supply systems in Texas .
2. Which federal law is the primary legislation governing public drinking
water safety in the United States?
A) Clean Water Act (CWA)
B) Resource Conservation and Recovery Act (RCRA)
C) Safe Drinking Water Act (SDWA)
D) National Environmental Policy Act (NEPA)
Answer C: Safe Drinking Water Act (SDWA)
,Rationale: The Safe Drinking Water Act (SDWA), enacted in 1974, is the primary
federal law that protects public drinking water supplies throughout the United
States .
3. What does MCL stand for in water quality regulations?
A) Maximum Contaminant Limit
B) Maximum Contaminant Level
C) Minimum Chlorine Limit
D) Mandatory Compliance Level
Answer B: Maximum Contaminant Level
Rationale: MCL stands for Maximum Contaminant Level, which is the highest
permissible level of a contaminant in drinking water. MCLs are enforceable
standards set by the EPA .
4. What is the MCLG for total coliforms in drinking water?
A) 1 CFU/100 mL
B) 5% positive samples per month
C) Zero
D) 0.5 CFU/100 mL
Answer C: Zero
Rationale: The Maximum Contaminant Level Goal (MCLG) for total coliforms is
zero because any coliform bacteria in drinking water may pose a health risk and
indicates possible contamination .
,5. Which of the following is a surface water source?
A) Artesian well
B) Confined aquifer
C) River
D) Water table well
Answer C: River
Rationale: Rivers are surface water sources. Surface water includes rivers, lakes,
reservoirs, and streams. Groundwater sources include wells and springs fed by
aquifers .
6. What is turbidity a measure of in water?
A) Bacterial count
B) Chemical oxygen demand
C) Cloudiness or haziness caused by suspended particles
D) Dissolved oxygen concentration
Answer C: Cloudiness or haziness caused by suspended particles
Rationale: Turbidity is a measure of water clarity. It reflects how much light is
scattered by suspended particles. High turbidity can interfere with disinfection .
7. What unit is turbidity measured in?
A) mg/L
, B) ppm
C) NTU (Nephelometric Turbidity Units)
D) JTU
Answer C: NTU (Nephelometric Turbidity Units)
Rationale: Turbidity is measured in Nephelometric Turbidity Units (NTU) using a
nephelometer, which measures light scattered at 90 degrees by suspended
particles .
8. The maximum turbidity allowed in treated drinking water leaving a
conventional filtration plant is:
A) 0.3 NTU for 95% of samples in a month
B) 0.5 NTU
C) 1.0 NTU
D) 5.0 NTU
Answer A: 0.3 NTU for 95% of samples in a month
Rationale: Conventional filtration plants must achieve turbidity ≤0.3 NTU in at
least 95% of monthly samples .
9. 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
D) Nothing unless two consecutive positives occur
