Class A Exam Practice Test Questions

Water System Operations Specialist Class A Exam Practice Test Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of a water distribution system?
• Treating water
• Storing water
• Delivering safe water to consumers
• Removing sediments
• Delivering safe water to consumers

Rationale: The distribution system's main function is to provide

potable water to consumers reliably and safely.

• Which chemical is commonly used for primary disinfection in water

systems? 1 / 4

• Fluoride
• Chlorine
• Alum
• Carbon dioxide
• Chlorine

Rationale: Chlorine is widely used due to its effectiveness in

inactivating pathogens and maintaining residual disinfectant in the distribution system.

• What is the primary function of a water storage tank?
• Treat water
• Maintain system pressure and storage
• Remove bacteria
• Regulate water temperature
• Maintain system pressure and storage

Rationale: Storage tanks ensure sufficient pressure in the system and

provide a buffer for peak demand periods.

• What does “residual chlorine” in a distribution system indicate?
• The amount of chlorine used in treatment
• The chlorine remaining to maintain disinfection
• Chlorine lost during treatment
• Chlorine combined with fluoride
• The chlorine remaining to maintain disinfection 2 / 4

Rationale: Residual chlorine ensures water remains protected from

microbial contamination as it travels through the system.

• Which device prevents backflow in a water distribution system?
• Pressure regulator
• Air relief valve
• Backflow preventer
• Hydrant
• Backflow preventer

Rationale: Backflow preventers stop contaminated water from

entering the potable water system.

• What is the main cause of water hammer in pipelines?
• High chlorine residual
• Rapid valve closure or pump shutdown
• Low pressure
• Sediment buildup
• Rapid valve closure or pump shutdown

Rationale: Sudden changes in flow can create pressure surges known

as water hammer, which can damage pipes and equipment.

• Which type of pump is commonly used in high-head applications in

water systems?

• Centrifugal pump
• Positive displacement pump
• Gear pump 3 / 4

• Diaphragm pump
• Centrifugal pump

Rationale: Centrifugal pumps are widely used in water systems and

can handle high-head and high-flow applications efficiently.

• Which parameter is most important for corrosion control in a

distribution system?

• pH
• Chlorine residual
• Fluoride
• Turbidity
• pH

Rationale: Maintaining proper pH reduces the corrosiveness of water

and protects metal pipes and infrastructure.

• What is the maximum contaminant level goal (MCLG) for arsenic in

drinking water?

• 0 mg/L
• 0.01 mg/L
• 0.05 mg/L
• 0.1 mg/L
• 0 mg/L

Rationale: The MCLG for arsenic is set at zero because it is a known

human carcinogen, although the enforceable MCL is 0.010 mg/L.

• / 4