Class D Water Operator License Exam TCEQ EXAM PREP QUESTIONS
AND CORRECT VERIFIED ANSWERS/ EXAM 2025/ S (NEW!)
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
e) all of the above - ANSWER-e) all of the above
, The purpose of an air line on a well is to:
a) aerate the well
b) determine the depth of the aquifer
c) inject chlorine into the well
d) allow the well to breathe
e) determine the water level - ANSWER-e) determine the water level
The drawdown of a well is determined by:
a) a properly installed air line
b) the difference between the static and pumping level
c) a psi gage calibrated in feet of water
d) a tape measure
e) an electronic sounder - ANSWER-b) the difference between the static and pumping level
A common type of oxidant that is used at most SW treatment plants to kill bacteria and to prevent
trihalomethane formation is:
a) total chlorine
b) combined chlorine
c) chlorine dioxide
d) free chlorine
e) ozonation - ANSWER-b) combined chlorine
A PWS is responsible for providing:
a) potable water
b) adequate water pressure
c) an adequate quantity of water
d) all of the above
e) soft water - ANSWER-d) all of the above
The amount of chlorine in mg/L that is used up by reactions with organics and inorganics is called:
a) dosage
AND CORRECT VERIFIED ANSWERS/ EXAM 2025/ S (NEW!)
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
e) all of the above - ANSWER-e) all of the above
, The purpose of an air line on a well is to:
a) aerate the well
b) determine the depth of the aquifer
c) inject chlorine into the well
d) allow the well to breathe
e) determine the water level - ANSWER-e) determine the water level
The drawdown of a well is determined by:
a) a properly installed air line
b) the difference between the static and pumping level
c) a psi gage calibrated in feet of water
d) a tape measure
e) an electronic sounder - ANSWER-b) the difference between the static and pumping level
A common type of oxidant that is used at most SW treatment plants to kill bacteria and to prevent
trihalomethane formation is:
a) total chlorine
b) combined chlorine
c) chlorine dioxide
d) free chlorine
e) ozonation - ANSWER-b) combined chlorine
A PWS is responsible for providing:
a) potable water
b) adequate water pressure
c) an adequate quantity of water
d) all of the above
e) soft water - ANSWER-d) all of the above
The amount of chlorine in mg/L that is used up by reactions with organics and inorganics is called:
a) dosage
