North Carolina Water Distribution System
Operator — Grade D Certification Exam
Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A | Instant
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1. What is the primary purpose of a water distribution system?
A. To treat water for contaminants
B. To deliver potable water to consumers
C. To monitor rainfall levels
D. To disinfect wastewater
Answer: B
Ensuring safe drinking water reaches consumers is the system’s main
function.
2. The minimum pressure required at all points in a water distribution
system under normal flow is:
A. 10 psi
B. 20 psi
C. 35 psi
D. 60 psi
Answer: C
Most regulations require at least 35 psi to maintain adequate service.
3. The term “head loss” refers to:
,A. Loss of water customers
B. Decrease in pH
C. Loss of pressure due to friction
D. Loss of chlorine
Answer: C
Friction inside pipes reduces pressure as water flows.
4. A corporation stop is used to:
A. Measure flow
B. Add chemicals
C. Connect a service line to a main
D. Vent air
Answer: C
It is the valve tapped directly into the water main.
5. The most common material for small-diameter distribution pipe
today is:
A. Cast iron
B. Lead
C. Concrete
D. PVC
Answer: D
PVC is lightweight, corrosion resistant, and widely used.
6. The component that controls the flow into a storage tank is the:
A. Check valve
B. Pressure gauge
C. Air release valve
D. Altitude valve
, Answer: D
Altitude valves prevent overflow by shutting at a preset level.
7. What is the primary purpose of a hydrant?
A. Customer water use
B. Pressure measurement
C. Fire protection and flushing
D. Valve isolation
Answer: C
Hydrants provide high-flow access for fire and maintenance.
8. A dead-end main may cause:
A. High velocity
B. Poor water circulation
C. Reduced pH
D. Low tank levels
Answer: B
Lack of circulation causes stagnation and chlorine loss.
9. A service line delivers water:
A. Into the distribution main
B. To fire hydrants
C. From the main to the customer
D. From pumps to tanks
Answer: C
Service lines connect customers to the system.
10. The device used to prevent backflow is called a:
Operator — Grade D Certification Exam
Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A | Instant
Download Pdf
1. What is the primary purpose of a water distribution system?
A. To treat water for contaminants
B. To deliver potable water to consumers
C. To monitor rainfall levels
D. To disinfect wastewater
Answer: B
Ensuring safe drinking water reaches consumers is the system’s main
function.
2. The minimum pressure required at all points in a water distribution
system under normal flow is:
A. 10 psi
B. 20 psi
C. 35 psi
D. 60 psi
Answer: C
Most regulations require at least 35 psi to maintain adequate service.
3. The term “head loss” refers to:
,A. Loss of water customers
B. Decrease in pH
C. Loss of pressure due to friction
D. Loss of chlorine
Answer: C
Friction inside pipes reduces pressure as water flows.
4. A corporation stop is used to:
A. Measure flow
B. Add chemicals
C. Connect a service line to a main
D. Vent air
Answer: C
It is the valve tapped directly into the water main.
5. The most common material for small-diameter distribution pipe
today is:
A. Cast iron
B. Lead
C. Concrete
D. PVC
Answer: D
PVC is lightweight, corrosion resistant, and widely used.
6. The component that controls the flow into a storage tank is the:
A. Check valve
B. Pressure gauge
C. Air release valve
D. Altitude valve
, Answer: D
Altitude valves prevent overflow by shutting at a preset level.
7. What is the primary purpose of a hydrant?
A. Customer water use
B. Pressure measurement
C. Fire protection and flushing
D. Valve isolation
Answer: C
Hydrants provide high-flow access for fire and maintenance.
8. A dead-end main may cause:
A. High velocity
B. Poor water circulation
C. Reduced pH
D. Low tank levels
Answer: B
Lack of circulation causes stagnation and chlorine loss.
9. A service line delivers water:
A. Into the distribution main
B. To fire hydrants
C. From the main to the customer
D. From pumps to tanks
Answer: C
Service lines connect customers to the system.
10. The device used to prevent backflow is called a:
