TEXAS CLASS D WATER LICENSE
PRACTICE QUESTIONS & ANSWERS
(COMPLETE SET)
Introduction
This 2025/2026 TCEQ Class D Water Operator License practice exam aligns with the
Texas Commission on Environmental Quality standards for entry-level operators,
covering basics, disinfection, safety, operations, math, and public health. Questions are
modeled after the 100-question exam (70% pass). Rationales reference TCEQ Class D
learning objectives, 30 TAC Chapter 290, and AWWA guidelines. Balanced distribution: 17
questions per domain. Use for certification prep; review TCEQ operator handbook.
Question [1]: As a Class D water operator, your primary responsibility is to?
A. Design new water systems
B. Monitor and maintain water quality and distribution
C. Perform advanced chemical analysis
D. Manage billing and customer service
Answer: B — Monitor and maintain water quality and distribution
Rationale: TCEQ Class D objectives emphasize basic operation and compliance with 30
TAC §290.38; design/advanced analysis for higher classes (A,C), billing administrative
(D).
Question [2]: The main components of a public water system include?
A. Only the treatment plant
B. Source, treatment, storage, and distribution
C. Billing software and meters
D. Laboratory equipment
Answer: B — Source, treatment, storage, and distribution
Rationale: TCEQ handbook: Full chain from raw water to consumer; treatment partial (A),
billing non-core (C), lab support (D).
,Question [3]: Water treatment processes typically begin with?
A. Disinfection
B. Coagulation and flocculation
C. pH adjustment
D. Filtration
Answer: B — Coagulation and flocculation
Rationale: TCEQ Class D: Removes particulates before sedimentation; disinfection final
(A), pH variable (C), filtration post (D).
Question [4]: A ground water source for a Class D system requires?
A. No treatment
B. Disinfection per Surface Water Treatment Rule
C. Chlorination only
D. Boiling
Answer: B — Disinfection per Surface Water Treatment Rule
Rationale: 30 TAC §290.109: GWR must disinfect for coliforms; no treatment risky (A),
chlorination one method (C), boiling not scalable (D).
Question [5]: The distribution system in a small Class D facility primarily ensures?
A. High pressure only
B. Adequate flow and pressure to consumers
C. Aesthetic quality
D. Color removal
Answer: B — Adequate flow and pressure to consumers
Rationale: TCEQ: Maintain 20-80 psi; pressure partial (A), aesthetic secondary (C,D).
Question [6]: Operator roles in a Class D system include reporting?
A. Monthly to TCEQ
B. Violations and monitoring results
C. Annual budgets
D. Daily weather
Answer: B — Violations and monitoring results
, Rationale: 30 TAC §290.38: Mandatory reporting for compliance; monthly specific (A),
budgets financial (C), weather irrelevant (D).
Question [7]: Chlorine residual in distribution system must be maintained at?
A. 0.0 mg/L
B. 0.2-4.0 mg/L
C. 5.0 mg/L
D. 10 mg/L
Answer: B — 0.2-4.0 mg/L
Rationale: TCEQ Class D: Minimum 0.2 mg/L free chlorine for disinfection; 0.0 none (A),
5-10 excessive taste (C,D).
Question [8]: The purpose of chlorine in water treatment is to?
A. Adjust pH
B. Disinfect and control microbial growth
C. Soften water
D. Remove color
Answer: B — Disinfect and control microbial growth
Rationale: TCEQ: Primary germicide; pH lime (A), softening zeolite (C), color activated
carbon (D).
Question [9]: Bacteriological sampling frequency for Class D system <25 connections?
A. Monthly
B. Quarterly
C. Annually
D. No sampling
Answer: A — Monthly
Rationale: 30 TAC §290.108: All systems monthly for coliforms; quarterly larger (B),
annual no (C,D).
Question [10]: Total coliform positive requires?
A. Ignore
B. Repeat and public notification if confirmed
C. Immediate shutdown
PRACTICE QUESTIONS & ANSWERS
(COMPLETE SET)
Introduction
This 2025/2026 TCEQ Class D Water Operator License practice exam aligns with the
Texas Commission on Environmental Quality standards for entry-level operators,
covering basics, disinfection, safety, operations, math, and public health. Questions are
modeled after the 100-question exam (70% pass). Rationales reference TCEQ Class D
learning objectives, 30 TAC Chapter 290, and AWWA guidelines. Balanced distribution: 17
questions per domain. Use for certification prep; review TCEQ operator handbook.
Question [1]: As a Class D water operator, your primary responsibility is to?
A. Design new water systems
B. Monitor and maintain water quality and distribution
C. Perform advanced chemical analysis
D. Manage billing and customer service
Answer: B — Monitor and maintain water quality and distribution
Rationale: TCEQ Class D objectives emphasize basic operation and compliance with 30
TAC §290.38; design/advanced analysis for higher classes (A,C), billing administrative
(D).
Question [2]: The main components of a public water system include?
A. Only the treatment plant
B. Source, treatment, storage, and distribution
C. Billing software and meters
D. Laboratory equipment
Answer: B — Source, treatment, storage, and distribution
Rationale: TCEQ handbook: Full chain from raw water to consumer; treatment partial (A),
billing non-core (C), lab support (D).
,Question [3]: Water treatment processes typically begin with?
A. Disinfection
B. Coagulation and flocculation
C. pH adjustment
D. Filtration
Answer: B — Coagulation and flocculation
Rationale: TCEQ Class D: Removes particulates before sedimentation; disinfection final
(A), pH variable (C), filtration post (D).
Question [4]: A ground water source for a Class D system requires?
A. No treatment
B. Disinfection per Surface Water Treatment Rule
C. Chlorination only
D. Boiling
Answer: B — Disinfection per Surface Water Treatment Rule
Rationale: 30 TAC §290.109: GWR must disinfect for coliforms; no treatment risky (A),
chlorination one method (C), boiling not scalable (D).
Question [5]: The distribution system in a small Class D facility primarily ensures?
A. High pressure only
B. Adequate flow and pressure to consumers
C. Aesthetic quality
D. Color removal
Answer: B — Adequate flow and pressure to consumers
Rationale: TCEQ: Maintain 20-80 psi; pressure partial (A), aesthetic secondary (C,D).
Question [6]: Operator roles in a Class D system include reporting?
A. Monthly to TCEQ
B. Violations and monitoring results
C. Annual budgets
D. Daily weather
Answer: B — Violations and monitoring results
, Rationale: 30 TAC §290.38: Mandatory reporting for compliance; monthly specific (A),
budgets financial (C), weather irrelevant (D).
Question [7]: Chlorine residual in distribution system must be maintained at?
A. 0.0 mg/L
B. 0.2-4.0 mg/L
C. 5.0 mg/L
D. 10 mg/L
Answer: B — 0.2-4.0 mg/L
Rationale: TCEQ Class D: Minimum 0.2 mg/L free chlorine for disinfection; 0.0 none (A),
5-10 excessive taste (C,D).
Question [8]: The purpose of chlorine in water treatment is to?
A. Adjust pH
B. Disinfect and control microbial growth
C. Soften water
D. Remove color
Answer: B — Disinfect and control microbial growth
Rationale: TCEQ: Primary germicide; pH lime (A), softening zeolite (C), color activated
carbon (D).
Question [9]: Bacteriological sampling frequency for Class D system <25 connections?
A. Monthly
B. Quarterly
C. Annually
D. No sampling
Answer: A — Monthly
Rationale: 30 TAC §290.108: All systems monthly for coliforms; quarterly larger (B),
annual no (C,D).
Question [10]: Total coliform positive requires?
A. Ignore
B. Repeat and public notification if confirmed
C. Immediate shutdown
