Virginia Waterworks Operator Class 5
Exam Questions With 100% Correct
Answers.
1. What is the minimum free chlorine residual required in the distribution system per
Virginia regulations?
A) 0.1 mg/L
B) 0.2 mg/L
C) 0.5 mg/L
D) 1.0 mg/L
Answer: B
Explanation: Virginia regulations require a minimum free chlorine residual of 0.2 mg/L in
the distribution system to ensure disinfection and prevent microbial regrowth.
2. A Class 5 operator is primarily responsible for:
A) Designing water treatment plants
B) Operating small waterworks under direct supervision
C) Managing statewide water permits
D) Performing laboratory certification
Answer: B
Explanation: Class 5 is the entry-level certification for small waterworks; operators work
under the supervision of a higher-class operator.
,3. Which chemical is most commonly used to adjust pH in drinking water?
A) Chlorine gas
B) Sodium hydroxide (caustic soda)
C) Ferric chloride
D) Potassium permanganate
Answer: B
Explanation: Sodium hydroxide raises pH; it is used to control corrosion and optimize
coagulation.
4. What is the purpose of a backflow prevention device?
A) Increase water pressure
B) Prevent contamination from cross-connections
C) Measure flow velocity
D) Filter sediment
Answer: B
Explanation: Backflow prevention stops reverse flow that could draw contaminants into
the public water system.
5. How often must a Class 5 waterworks collect bacteriological samples?
A) Once per week
B) Once per month
C) Once per quarter
D) Daily
,Answer: B
Explanation: Small systems typically collect at least one routine bacteriological sample
per month, per Virginia requirements.
6. The maximum contaminant level (MCL) for total coliform bacteria is:
A) 5% positive samples
B) No more than 1 positive sample per month for systems collecting ≥40 samples
C) Zero tolerance for all systems
D) 10% positive samples
Answer: B
Explanation: For systems collecting at least 40 samples/month, no more than 5%
positive; for smaller, any positive is a violation unless repeat samples are all negative.
7. A chlorine gas leak can be detected by:
A) Rotten egg smell
B) Bleach smell and white cloud
C) Sweet odor
D) No odor at all
Answer: B
Explanation: Chlorine gas has a pungent bleach-like odor and forms a greenish-white
cloud when leaking.
, 8. The safe storage capacity for a water storage tank should be at least:
A) 1 day of average demand
B) 1 day of peak demand
C) 50% of daily flow
D) Depends on system size but often 1 day’s average demand
Answer: D
Explanation: Storage should meet peak and emergency needs; typical design is one day
of average demand.
9. Which valve is used to regulate flow in a pipe?
A) Gate valve
B) Butterfly valve
C) Globe valve
D) Check valve
Answer: C
Explanation: Globe valves are designed for throttling flow; gate valves are for on/off,
check valves prevent backflow.
10. What does SCADA stand for?
A) Systematic Control and Data Acquisition
B) Supervisory Control and Data Acquisition
C) Safety Control and Distribution Alert
D) Source Collection and Distribution Agency
Exam Questions With 100% Correct
Answers.
1. What is the minimum free chlorine residual required in the distribution system per
Virginia regulations?
A) 0.1 mg/L
B) 0.2 mg/L
C) 0.5 mg/L
D) 1.0 mg/L
Answer: B
Explanation: Virginia regulations require a minimum free chlorine residual of 0.2 mg/L in
the distribution system to ensure disinfection and prevent microbial regrowth.
2. A Class 5 operator is primarily responsible for:
A) Designing water treatment plants
B) Operating small waterworks under direct supervision
C) Managing statewide water permits
D) Performing laboratory certification
Answer: B
Explanation: Class 5 is the entry-level certification for small waterworks; operators work
under the supervision of a higher-class operator.
,3. Which chemical is most commonly used to adjust pH in drinking water?
A) Chlorine gas
B) Sodium hydroxide (caustic soda)
C) Ferric chloride
D) Potassium permanganate
Answer: B
Explanation: Sodium hydroxide raises pH; it is used to control corrosion and optimize
coagulation.
4. What is the purpose of a backflow prevention device?
A) Increase water pressure
B) Prevent contamination from cross-connections
C) Measure flow velocity
D) Filter sediment
Answer: B
Explanation: Backflow prevention stops reverse flow that could draw contaminants into
the public water system.
5. How often must a Class 5 waterworks collect bacteriological samples?
A) Once per week
B) Once per month
C) Once per quarter
D) Daily
,Answer: B
Explanation: Small systems typically collect at least one routine bacteriological sample
per month, per Virginia requirements.
6. The maximum contaminant level (MCL) for total coliform bacteria is:
A) 5% positive samples
B) No more than 1 positive sample per month for systems collecting ≥40 samples
C) Zero tolerance for all systems
D) 10% positive samples
Answer: B
Explanation: For systems collecting at least 40 samples/month, no more than 5%
positive; for smaller, any positive is a violation unless repeat samples are all negative.
7. A chlorine gas leak can be detected by:
A) Rotten egg smell
B) Bleach smell and white cloud
C) Sweet odor
D) No odor at all
Answer: B
Explanation: Chlorine gas has a pungent bleach-like odor and forms a greenish-white
cloud when leaking.
, 8. The safe storage capacity for a water storage tank should be at least:
A) 1 day of average demand
B) 1 day of peak demand
C) 50% of daily flow
D) Depends on system size but often 1 day’s average demand
Answer: D
Explanation: Storage should meet peak and emergency needs; typical design is one day
of average demand.
9. Which valve is used to regulate flow in a pipe?
A) Gate valve
B) Butterfly valve
C) Globe valve
D) Check valve
Answer: C
Explanation: Globe valves are designed for throttling flow; gate valves are for on/off,
check valves prevent backflow.
10. What does SCADA stand for?
A) Systematic Control and Data Acquisition
B) Supervisory Control and Data Acquisition
C) Safety Control and Distribution Alert
D) Source Collection and Distribution Agency
