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CLASS D WATER OPERATOR License Exam TCEQ
Comprehensive Questions and Verified Detailed
Answers 2026
Meter readers bring in operating revenue and profoundly impact
_____ relations.
Public
The federal regulator of drinking water is the _____.
EPA
T/F: Duties of distribution operator include repairing leaks, making
taps, flushing mains, and taking radiological samples.
False (Repair leaks, Make taps, Flush mains, Operate pumps,
Take bacteriological samples)
A service area has 1000 service connections. What can we estimate
the population of this service area to be?
3,000 (multiply connections x 3)
T/F: The State must be notified after an existing facility is changed or
after construction of a new facility.
False (must notify before)
T/F: A Class "D" license is valid for 2 years at ground and purchase
water systems with 250 connections or less.
False (3 years)
T/F: The physical characteristics of water are color, taste, odor,
temperature, and turbidity.
True
An alkaline or basic solution has a pH greater than ____.
7
T/F: The terms mg/L and ppm are not interchangeable.
False (they are interchangeable)
Suspended solids in water cannot be filtered out.
False (they can)
Solids, water hardness, pH and gases are ____ characteristics.
Chemical
T/F: There are 2 hydrogen atoms and 1 oxygen atom in each water
molecule.
,2
True
T/F: The State recommends a water pH of less than 7 to be maintained
at all time.
False (The state recommends a pH slightly greater than 7 and for the water
to be non-corrosive.)
T/F: Taste and odor can come from organisms such as vegetation,
bacteria, and algae, and from certain chemicals and metals.
True
T/F: The deeper the well, the warmer the water.
True
T/F: The threshold odor number (TON) relates to the number of
dilutions needed for the water to be tasteless.
False (It reflects the number of dilutions needed for water sample to
be odorless)
One part per million or 1 mg/L means that for every ____ pounds of
water there is one pound of material in it.
1 million
The State requires filtered water to be equal to or less than ____
turbidity units in at least 95% of the monthly samples.
0.3
The State recommends a TON of ___ or less.
3
T/F: The State recommends 20 color units or less for a quality water.
False (The state recommends 15 units of color or less for drinking water.)
T/F: Examples of inorganic matter found in water include rock, sand,
metals, and minerals.
True
T/F: The red color caused by iron is an example of suspended or
apparent color and it can be removed by filtration.
True
Excessive calcium and _____ are the primary cause of hardness in
water.
Magnesium
T/F: The State recommends a maximum total dissolved solids content
of 500 mg/L
False (The state recommends that TDS not exceed 1000 mg/L)
, 3
There are 3 common gases found in water: methane, carbon dioxide,
and __________ ___________.
hydrogen sulfide
T/F: Turbidity must be limited because it shelters and nourishes
bacteria and interferes with disinfection.
True
T/F: Bleach or alcohol require less contact time than flaming to
disinfect a faucet.
False (flaming requires less contact time)
T/F: The "primary limits" refer to chemicals with maximum
contaminant levels that can be exceeded.
False (refers to chemicals with maximum contaminant levels (MCLs)
that CANNOT be exceeded.)
T/F: The term "total coliform" means fecal and non-fecal coliform.
True
T/F: Pathogens are disease-causing microorganisms.
True
If a routine sample is positive, flush the positive sample point, check
the chlorine residual, then resample within 24 days of notification.
False (If a routine sample is total coliform-positive, the PWS should flush
the positive sample point, check the chlorine residual, then resample
within 24 hrs of notification)
To prevent the formation of THMS in surface water, chlorine is
combined with _____ forming chloramine, combined chlorine
residual.
Ammonia
If there is no chlorine ______ at a faucet, do not sample, flush longer.
residual
T/F: All repeat samples must be collected on successive days.
False (Collect all repeat sample on the same day)
In the event of distribution pressure below ___ psi, _______ outages,
repeated bad samples or chlorine _____ below minimum, special
precautions must be instituted.
20/water/residual
Get the sample to the lab within ___________ or it will be rejected.
30 hours (for BacT samples)
CLASS D WATER OPERATOR License Exam TCEQ
Comprehensive Questions and Verified Detailed
Answers 2026
Meter readers bring in operating revenue and profoundly impact
_____ relations.
Public
The federal regulator of drinking water is the _____.
EPA
T/F: Duties of distribution operator include repairing leaks, making
taps, flushing mains, and taking radiological samples.
False (Repair leaks, Make taps, Flush mains, Operate pumps,
Take bacteriological samples)
A service area has 1000 service connections. What can we estimate
the population of this service area to be?
3,000 (multiply connections x 3)
T/F: The State must be notified after an existing facility is changed or
after construction of a new facility.
False (must notify before)
T/F: A Class "D" license is valid for 2 years at ground and purchase
water systems with 250 connections or less.
False (3 years)
T/F: The physical characteristics of water are color, taste, odor,
temperature, and turbidity.
True
An alkaline or basic solution has a pH greater than ____.
7
T/F: The terms mg/L and ppm are not interchangeable.
False (they are interchangeable)
Suspended solids in water cannot be filtered out.
False (they can)
Solids, water hardness, pH and gases are ____ characteristics.
Chemical
T/F: There are 2 hydrogen atoms and 1 oxygen atom in each water
molecule.
,2
True
T/F: The State recommends a water pH of less than 7 to be maintained
at all time.
False (The state recommends a pH slightly greater than 7 and for the water
to be non-corrosive.)
T/F: Taste and odor can come from organisms such as vegetation,
bacteria, and algae, and from certain chemicals and metals.
True
T/F: The deeper the well, the warmer the water.
True
T/F: The threshold odor number (TON) relates to the number of
dilutions needed for the water to be tasteless.
False (It reflects the number of dilutions needed for water sample to
be odorless)
One part per million or 1 mg/L means that for every ____ pounds of
water there is one pound of material in it.
1 million
The State requires filtered water to be equal to or less than ____
turbidity units in at least 95% of the monthly samples.
0.3
The State recommends a TON of ___ or less.
3
T/F: The State recommends 20 color units or less for a quality water.
False (The state recommends 15 units of color or less for drinking water.)
T/F: Examples of inorganic matter found in water include rock, sand,
metals, and minerals.
True
T/F: The red color caused by iron is an example of suspended or
apparent color and it can be removed by filtration.
True
Excessive calcium and _____ are the primary cause of hardness in
water.
Magnesium
T/F: The State recommends a maximum total dissolved solids content
of 500 mg/L
False (The state recommends that TDS not exceed 1000 mg/L)
, 3
There are 3 common gases found in water: methane, carbon dioxide,
and __________ ___________.
hydrogen sulfide
T/F: Turbidity must be limited because it shelters and nourishes
bacteria and interferes with disinfection.
True
T/F: Bleach or alcohol require less contact time than flaming to
disinfect a faucet.
False (flaming requires less contact time)
T/F: The "primary limits" refer to chemicals with maximum
contaminant levels that can be exceeded.
False (refers to chemicals with maximum contaminant levels (MCLs)
that CANNOT be exceeded.)
T/F: The term "total coliform" means fecal and non-fecal coliform.
True
T/F: Pathogens are disease-causing microorganisms.
True
If a routine sample is positive, flush the positive sample point, check
the chlorine residual, then resample within 24 days of notification.
False (If a routine sample is total coliform-positive, the PWS should flush
the positive sample point, check the chlorine residual, then resample
within 24 hrs of notification)
To prevent the formation of THMS in surface water, chlorine is
combined with _____ forming chloramine, combined chlorine
residual.
Ammonia
If there is no chlorine ______ at a faucet, do not sample, flush longer.
residual
T/F: All repeat samples must be collected on successive days.
False (Collect all repeat sample on the same day)
In the event of distribution pressure below ___ psi, _______ outages,
repeated bad samples or chlorine _____ below minimum, special
precautions must be instituted.
20/water/residual
Get the sample to the lab within ___________ or it will be rejected.
30 hours (for BacT samples)
