North Carolina Water Distribution System
Operator — Grade A 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. Increase groundwater recharge
B. Deliver safe, potable water to consumers
C. Maintain wastewater flow to treatment plants
D. Reduce chlorine decay
*Rationale: Providing safe drinking water is the core purpose of a
distribution system.
2. Hydrostatic pressure in a distribution main is primarily created by:
A. Consumer demand
B. Pumps and elevation differences
C. Temperature variations
D. Service connections
*Rationale: Pressure comes from pumps or gravity due to elevation.
3. A water main is typically defined as a pipe that:
,A. Feeds a single home
B. Supplies only hydrants
C. Supplies multiple service connections or hydrants
D. Carries raw water only
*Rationale: Mains serve multiple customers or hydrants.
4. Which unit measures water pressure?
A. Gallons per minute
B. Micromhos
C. Pounds per square inch (psi)
D. Milligrams per liter
*Rationale: Pressure is expressed in psi.
5. The recommended minimum pressure in a distribution system
during normal operation is:
A. 10 psi
B. 20 psi
C. 35 psi
D. 5 psi
*Rationale: Most systems target at least ~35 psi for adequate service.
6. Chlorine residual must be maintained to:
A. Reduce hardness
B. Prevent microbial contamination
C. Remove turbidity
, D. Bind metals
*Rationale: Residual chlorine prevents pathogen growth.
7. Water hammer is caused by:
A. Low chlorine levels
B. High temperatures
C. Sudden changes in flow velocity
D. pH fluctuations
*Rationale: Rapid valve closures or pump changes create water
hammer.
8. A gate valve is best used for:
A. Throttling flow
B. Full open or full close operation
C. Pressure regulation
D. Air release
*Rationale: Gate valves are not designed for throttling.
9. Which pipe material is most resistant to corrosion?
A. Unlined steel
B. Cast iron
C. PVC
D. Plain iron
*Rationale: PVC is non-metallic and corrosion-resistant.
Operator — Grade A 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. Increase groundwater recharge
B. Deliver safe, potable water to consumers
C. Maintain wastewater flow to treatment plants
D. Reduce chlorine decay
*Rationale: Providing safe drinking water is the core purpose of a
distribution system.
2. Hydrostatic pressure in a distribution main is primarily created by:
A. Consumer demand
B. Pumps and elevation differences
C. Temperature variations
D. Service connections
*Rationale: Pressure comes from pumps or gravity due to elevation.
3. A water main is typically defined as a pipe that:
,A. Feeds a single home
B. Supplies only hydrants
C. Supplies multiple service connections or hydrants
D. Carries raw water only
*Rationale: Mains serve multiple customers or hydrants.
4. Which unit measures water pressure?
A. Gallons per minute
B. Micromhos
C. Pounds per square inch (psi)
D. Milligrams per liter
*Rationale: Pressure is expressed in psi.
5. The recommended minimum pressure in a distribution system
during normal operation is:
A. 10 psi
B. 20 psi
C. 35 psi
D. 5 psi
*Rationale: Most systems target at least ~35 psi for adequate service.
6. Chlorine residual must be maintained to:
A. Reduce hardness
B. Prevent microbial contamination
C. Remove turbidity
, D. Bind metals
*Rationale: Residual chlorine prevents pathogen growth.
7. Water hammer is caused by:
A. Low chlorine levels
B. High temperatures
C. Sudden changes in flow velocity
D. pH fluctuations
*Rationale: Rapid valve closures or pump changes create water
hammer.
8. A gate valve is best used for:
A. Throttling flow
B. Full open or full close operation
C. Pressure regulation
D. Air release
*Rationale: Gate valves are not designed for throttling.
9. Which pipe material is most resistant to corrosion?
A. Unlined steel
B. Cast iron
C. PVC
D. Plain iron
*Rationale: PVC is non-metallic and corrosion-resistant.
