Page 1 of 89
Class D Water License Texas Latest Update
Exam 2026 Questions And Answers
(Verified Answers), 100% Guaranteed Pass
||Complete A+ Guide
1. In Texas, all public water systems must have which type
of facilities?
a) Filtration
b) Fluoridation
c) Chlorination
d) Softening
Answer: c) Chlorination
Rationale: TCEQ rules (30 TAC 290) require chlorination
,Page 2 of 89
facilities for all public water systems to ensure disinfection and
protect public health.
2. What is the maximum time a Class D license is valid for a
system with 250 connections or less?
a) 1 year
b) 2 years
c) 3 years
d) 5 years
Answer: c) 3 years
Rationale: Unlike higher licenses that renew annually, Class D
licenses for small systems are valid for three years.
3. (Scenario) You are the operator of a rural water supply. A
customer calls and says their water is suddenly "milky"
white. After running the tap for 5 minutes, it clears up from
the bottom up. What is the most likely cause?
a) High iron content
b) Air entrainment (Air in the line)
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c) Chlorine gas leak
d) Sewage contamination
Answer: b) Air entrainment
Rationale: Milky water that clears from the bottom up
indicates tiny air bubbles. This is physical, not chemical, and
usually harmless. Contamination or gas leaks have different
odors/appearances.
4. The federal regulatory agency that sets drinking water
standards is the:
a) TCEQ
b) EPA
c) TWDB
d) OSHA
Answer: b) EPA
Rationale: The Environmental Protection Agency (EPA) sets the
national standards under the Safe Drinking Water Act, while
TCEQ enforces them in Texas.
, Page 4 of 89
5. (Scenario) A routine bacteriological sample comes back p. p. p. p. p. p.
p. "Total Coliform Positive." What is the immediate next step
p. p. p. p. p. p. p. p.
p. for the operator?
p. p.
a) Wait for the next scheduled sample day
p. p. p. p. p. p.
b) Boil the water notice
p. p. p.
c) Collect repeat samples within 24 hours
p. p. p. p. p.
d) Increase the chlorine to 10.0 mg/L p. p. p. p. p.
Answer: c) Collect repeat samples within 24 hours
p. p. p. p. p. p. p.
Rationale: The rule requires resampling at the original site and
p. p. p. p. p. p. p. p. p.
p. within 5 connections upstream/downstream within 24 hours of
p. p. p. p. p. p. p.
p. notification. A boil notice is not required until a confirmed positive
p. p. p. p. p. p. p. p. p. p.
p. (E. coli or repeat positives).
p. p. p. p.
6. According to TCEQ, "Potable" water means: p. p. p. p. p.
a) Water that tastes good p. p. p.
b) Water that is safe to drink and has a measurable chlorine
p. p. p. p. p. p. p. p. p. p.
p. residual
c) Distilled water only p. p.
d) Water that is soft p. p. p.
Class D Water License Texas Latest Update
Exam 2026 Questions And Answers
(Verified Answers), 100% Guaranteed Pass
||Complete A+ Guide
1. In Texas, all public water systems must have which type
of facilities?
a) Filtration
b) Fluoridation
c) Chlorination
d) Softening
Answer: c) Chlorination
Rationale: TCEQ rules (30 TAC 290) require chlorination
,Page 2 of 89
facilities for all public water systems to ensure disinfection and
protect public health.
2. What is the maximum time a Class D license is valid for a
system with 250 connections or less?
a) 1 year
b) 2 years
c) 3 years
d) 5 years
Answer: c) 3 years
Rationale: Unlike higher licenses that renew annually, Class D
licenses for small systems are valid for three years.
3. (Scenario) You are the operator of a rural water supply. A
customer calls and says their water is suddenly "milky"
white. After running the tap for 5 minutes, it clears up from
the bottom up. What is the most likely cause?
a) High iron content
b) Air entrainment (Air in the line)
,Page 3 of 89
c) Chlorine gas leak
d) Sewage contamination
Answer: b) Air entrainment
Rationale: Milky water that clears from the bottom up
indicates tiny air bubbles. This is physical, not chemical, and
usually harmless. Contamination or gas leaks have different
odors/appearances.
4. The federal regulatory agency that sets drinking water
standards is the:
a) TCEQ
b) EPA
c) TWDB
d) OSHA
Answer: b) EPA
Rationale: The Environmental Protection Agency (EPA) sets the
national standards under the Safe Drinking Water Act, while
TCEQ enforces them in Texas.
, Page 4 of 89
5. (Scenario) A routine bacteriological sample comes back p. p. p. p. p. p.
p. "Total Coliform Positive." What is the immediate next step
p. p. p. p. p. p. p. p.
p. for the operator?
p. p.
a) Wait for the next scheduled sample day
p. p. p. p. p. p.
b) Boil the water notice
p. p. p.
c) Collect repeat samples within 24 hours
p. p. p. p. p.
d) Increase the chlorine to 10.0 mg/L p. p. p. p. p.
Answer: c) Collect repeat samples within 24 hours
p. p. p. p. p. p. p.
Rationale: The rule requires resampling at the original site and
p. p. p. p. p. p. p. p. p.
p. within 5 connections upstream/downstream within 24 hours of
p. p. p. p. p. p. p.
p. notification. A boil notice is not required until a confirmed positive
p. p. p. p. p. p. p. p. p. p.
p. (E. coli or repeat positives).
p. p. p. p.
6. According to TCEQ, "Potable" water means: p. p. p. p. p.
a) Water that tastes good p. p. p.
b) Water that is safe to drink and has a measurable chlorine
p. p. p. p. p. p. p. p. p. p.
p. residual
c) Distilled water only p. p.
d) Water that is soft p. p. p.
