TCEQ Class D Water Operator License Practice Exam by Texas
Commission on Environmental Quality (TCEQ) Training Staff
2026/2027| Actual Complete Questions and Verified
Answers| 100% Success(A+)
T/F: In Texas, about 75% of all water is used for commercial, industrial, or agricultural
purposes. - ✔✔✔ ANSWER-True
Water covers approximately ________ of Earth's surface. - ✔✔✔ ANSWER-71%
The pH of water indicates whether it is acidic or basic and is expressed by a scale of
numbers ranging from:
a) 0 - 7
b) 0 - 14
c) 1 - 7
d) 1 - 14
e) none of the above - ✔✔✔ ANSWER-b) 0 - 14
Before a new main is placed into service, it must be properly disinfected with a
minimum chlorine dosage of:
a) 50 mg/L
b) 30 mg/L
c) 40 mg/L
,d) 75 mg/L
e) 25 mg/L - ✔✔✔ ANSWER-a) 50 mg/L
A common chemical used for disinfecting a small public water supply is:
a) soda ash
b) copper sulfate
c) sodium hypochlorite
d) fluoride
e) sodium chloride - ✔✔✔ ANSWER-c) sodium hypochlorite
Gravity filters will remove which of the following from surface water supplies:
a) turbidity
b) taste and odors
c) nitrates
d) hardness
e) chlorides - ✔✔✔ ANSWER-a) turbidity
If you added 3.5 mg/L of chlorine to your storage tank and 30 minutes later measured
the residual at 1.2 mg/L, what was the chlorine demand in the tank?
a) 4.2
b) 2.9
c) 0.3
d) 2.3
, e) 4.7 - ✔✔✔ ANSWER-d) 2.3
Your ground storage tank is 15 feet high and 30 feet in diameter. About how much
water can it hold?
a) 31,700 gallons
b) 79,270 gallons
c) 50, 490 gallons
d) 25,150 gallons
e) 10,600 gallons - ✔✔✔ ANSWER-...
When fecal coliform organisms are found in a water supply, it is an indication that:
a) the water supply is contaminated
b) pathogenic organisms might be present
c) the water may be unsuitable for drinking
d) follow-up sampling must take place
e) all of the above - ✔✔✔ ANSWER-e) all of the above
Which of the following is an acceptable level of residual chlorine in the far reaches of a
distribution system?
a) 0.2 mg/L of free chlorine for a small GWS
b) 0.5 mg/L of chloramine for a large SWS
c) 1.0 mg/L of combined when using ammoniation facilities
d) 1.0 mg/L of total for a large SWS
Commission on Environmental Quality (TCEQ) Training Staff
2026/2027| Actual Complete Questions and Verified
Answers| 100% Success(A+)
T/F: In Texas, about 75% of all water is used for commercial, industrial, or agricultural
purposes. - ✔✔✔ ANSWER-True
Water covers approximately ________ of Earth's surface. - ✔✔✔ ANSWER-71%
The pH of water indicates whether it is acidic or basic and is expressed by a scale of
numbers ranging from:
a) 0 - 7
b) 0 - 14
c) 1 - 7
d) 1 - 14
e) none of the above - ✔✔✔ ANSWER-b) 0 - 14
Before a new main is placed into service, it must be properly disinfected with a
minimum chlorine dosage of:
a) 50 mg/L
b) 30 mg/L
c) 40 mg/L
,d) 75 mg/L
e) 25 mg/L - ✔✔✔ ANSWER-a) 50 mg/L
A common chemical used for disinfecting a small public water supply is:
a) soda ash
b) copper sulfate
c) sodium hypochlorite
d) fluoride
e) sodium chloride - ✔✔✔ ANSWER-c) sodium hypochlorite
Gravity filters will remove which of the following from surface water supplies:
a) turbidity
b) taste and odors
c) nitrates
d) hardness
e) chlorides - ✔✔✔ ANSWER-a) turbidity
If you added 3.5 mg/L of chlorine to your storage tank and 30 minutes later measured
the residual at 1.2 mg/L, what was the chlorine demand in the tank?
a) 4.2
b) 2.9
c) 0.3
d) 2.3
, e) 4.7 - ✔✔✔ ANSWER-d) 2.3
Your ground storage tank is 15 feet high and 30 feet in diameter. About how much
water can it hold?
a) 31,700 gallons
b) 79,270 gallons
c) 50, 490 gallons
d) 25,150 gallons
e) 10,600 gallons - ✔✔✔ ANSWER-...
When fecal coliform organisms are found in a water supply, it is an indication that:
a) the water supply is contaminated
b) pathogenic organisms might be present
c) the water may be unsuitable for drinking
d) follow-up sampling must take place
e) all of the above - ✔✔✔ ANSWER-e) all of the above
Which of the following is an acceptable level of residual chlorine in the far reaches of a
distribution system?
a) 0.2 mg/L of free chlorine for a small GWS
b) 0.5 mg/L of chloramine for a large SWS
c) 1.0 mg/L of combined when using ammoniation facilities
d) 1.0 mg/L of total for a large SWS
