Page 1 of 59
NORTH CAROLINA WATER DISTRIBUTION GRADE C CERTIFICATION EXAM
— COMPREHENSIVE —EXAM QUESTIONS LATEST EDITION 2026 – 2027
VERSION SOLVED QUESTIONS & ANSWERS
Q1. What is the primary purpose of a public water distribution system?
A) To treat wastewater for disposal
B) To deliver safe drinking water to consumers for residential, commercial, industrial,
and fire protection uses
C) To store water for agricultural use
D) To generate hydroelectric power
Correct Answer: B
Rationale: The distribution system's primary purpose is to transport potable water
safely from the treatment plant to consumers, including residential, commercial,
industrial, and fire protection uses. It must deliver water that is free of cross-
connections with unapproved sources and other potential contaminants .
Q2. Which of the following is NOT a component of a public water distribution
system?
A) Storage tanks
B) Pump stations
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C) Wastewater treatment plant
D) Service lines
Correct Answer: C
Rationale: A wastewater treatment plant is part of the wastewater collection and
treatment system, not the drinking water distribution system. Distribution system
components include pipes, valves, hydrants, service lines, meters, pump stations, and
storage tanks .
Q3. What is the definition of a public water system under North Carolina rules?
A) Any system that provides water for human consumption to 15 or more service
connections
B) Any system that provides water to at least 25 people daily for 60 or more days per
year
C) Both A and B
D) Any private well serving a single household
Correct Answer: C
Rationale: A public water system delivers water to customers for human consumption
and serves at least 15 service connections or regularly serves at least 25 people daily
for 60 or more days per year. It must be free of cross-connections with unapproved
water sources .
Q4. Which federal law provides uniform national standards for drinking water
quality?
A) Clean Water Act
B) Safe Drinking Water Act
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C) Resource Conservation and Recovery Act
D) Clean Air Act
Correct Answer: B
Rationale: The Safe Drinking Water Act (SDWA) provides uniform national standards for
drinking water quality, establishing maximum contaminant levels (MCLs) and treatment
requirements for public water systems .
Q5. What is the primary function of transmission mains in a water distribution
system?
A) To carry water directly to individual homes
B) To transport large volumes of water across the system
C) To store water for emergency use
D) To treat water before distribution
Correct Answer: B
Rationale: Transmission mains transport large volumes of water from treatment
facilities or wells to various parts of the distribution system. Distribution pipes carry
water to individual customers and are smaller than transmission mains .
Q6. What are the two main sources of drinking water?
A) Rivers and lakes only
B) Surface water and groundwater
C) Wells and reservoirs
D) Precipitation and runoff
Correct Answer: B
Rationale: The two main sources of drinking water are surface water (rivers, lakes,
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reservoirs) and groundwater (wells, aquifers). Both require treatment before distribution
to consumers .
Q7. What is the primary purpose of a fire hydrant in a water distribution system?
A) To measure water flow for billing purposes
B) To provide water for firefighting and emergency purposes
C) To reduce system pressure during peak demand
D) To add chlorine to the distribution system
Correct Answer: B
Rationale: Fire hydrants provide immediate access to water for firefighting. They also
serve secondary purposes including flushing mains and providing water for
construction .
Q8. Which type of valve is typically used to isolate a section of a distribution
system for maintenance?
A) Pressure relief valve
B) Check valve
C) Gate valve
D) Air release valve
Correct Answer: C
Rationale: Gate valves are designed to completely stop or allow flow in a distribution
main. They provide full shutoff with minimal friction loss when fully open, making them
ideal for isolation purposes .
Q9. A water system customer reports low pressure at their residence. Which of the
following is the most likely cause?
NORTH CAROLINA WATER DISTRIBUTION GRADE C CERTIFICATION EXAM
— COMPREHENSIVE —EXAM QUESTIONS LATEST EDITION 2026 – 2027
VERSION SOLVED QUESTIONS & ANSWERS
Q1. What is the primary purpose of a public water distribution system?
A) To treat wastewater for disposal
B) To deliver safe drinking water to consumers for residential, commercial, industrial,
and fire protection uses
C) To store water for agricultural use
D) To generate hydroelectric power
Correct Answer: B
Rationale: The distribution system's primary purpose is to transport potable water
safely from the treatment plant to consumers, including residential, commercial,
industrial, and fire protection uses. It must deliver water that is free of cross-
connections with unapproved sources and other potential contaminants .
Q2. Which of the following is NOT a component of a public water distribution
system?
A) Storage tanks
B) Pump stations
, Page 2 of 59
C) Wastewater treatment plant
D) Service lines
Correct Answer: C
Rationale: A wastewater treatment plant is part of the wastewater collection and
treatment system, not the drinking water distribution system. Distribution system
components include pipes, valves, hydrants, service lines, meters, pump stations, and
storage tanks .
Q3. What is the definition of a public water system under North Carolina rules?
A) Any system that provides water for human consumption to 15 or more service
connections
B) Any system that provides water to at least 25 people daily for 60 or more days per
year
C) Both A and B
D) Any private well serving a single household
Correct Answer: C
Rationale: A public water system delivers water to customers for human consumption
and serves at least 15 service connections or regularly serves at least 25 people daily
for 60 or more days per year. It must be free of cross-connections with unapproved
water sources .
Q4. Which federal law provides uniform national standards for drinking water
quality?
A) Clean Water Act
B) Safe Drinking Water Act
, Page 3 of 59
C) Resource Conservation and Recovery Act
D) Clean Air Act
Correct Answer: B
Rationale: The Safe Drinking Water Act (SDWA) provides uniform national standards for
drinking water quality, establishing maximum contaminant levels (MCLs) and treatment
requirements for public water systems .
Q5. What is the primary function of transmission mains in a water distribution
system?
A) To carry water directly to individual homes
B) To transport large volumes of water across the system
C) To store water for emergency use
D) To treat water before distribution
Correct Answer: B
Rationale: Transmission mains transport large volumes of water from treatment
facilities or wells to various parts of the distribution system. Distribution pipes carry
water to individual customers and are smaller than transmission mains .
Q6. What are the two main sources of drinking water?
A) Rivers and lakes only
B) Surface water and groundwater
C) Wells and reservoirs
D) Precipitation and runoff
Correct Answer: B
Rationale: The two main sources of drinking water are surface water (rivers, lakes,
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reservoirs) and groundwater (wells, aquifers). Both require treatment before distribution
to consumers .
Q7. What is the primary purpose of a fire hydrant in a water distribution system?
A) To measure water flow for billing purposes
B) To provide water for firefighting and emergency purposes
C) To reduce system pressure during peak demand
D) To add chlorine to the distribution system
Correct Answer: B
Rationale: Fire hydrants provide immediate access to water for firefighting. They also
serve secondary purposes including flushing mains and providing water for
construction .
Q8. Which type of valve is typically used to isolate a section of a distribution
system for maintenance?
A) Pressure relief valve
B) Check valve
C) Gate valve
D) Air release valve
Correct Answer: C
Rationale: Gate valves are designed to completely stop or allow flow in a distribution
main. They provide full shutoff with minimal friction loss when fully open, making them
ideal for isolation purposes .
Q9. A water system customer reports low pressure at their residence. Which of the
following is the most likely cause?
