North Carolina (NC) Public Utilities Contractor
Actual Question Comprehensive Practice Exam
with Verified Answers and Detailed Rationales
(2025/2026 Edition)|PDF
Overview:
This Real exam is specifically designed for contractors preparing for the North Carolina Public
Utilities (PU) licensing exam. It contains 300 realistic, multiple-choice questions covering all
critical topics necessary for exam success, including:
Key Topics Covered:
1. Water Distribution Systems
o Water main installation, jointing methods, and pipe materials
o Valves (gate, check, globe, pressure-reducing)
o Fire hydrants, blow-offs, and pressure testing
o Thrust blocks, deadman anchors, and air release valves
o Hydraulic grade line and pressure calculations
2. Sewer Collection Systems
o Gravity and force main design
o Slope requirements and self-cleansing velocity
o Manholes, cleanouts, and drop connections
o Sewer force mains and lift stations
o PVC, ductile iron, and concrete pipe materials
3. Stormwater Management & BMPs
o Infiltration basins, swales, and erosion control
o Environmental compliance and best management practices
4. Backflow Prevention & Cross-Connection Control
o Check valves, double check assemblies, and RPZ devices
o Prevention of contamination in potable water systems
5. Construction Safety & Regulations
o Trench safety (shoring, sloping, protective systems)
o OSHA requirements and utility safety
o Call Before You Dig (811) procedures
6. Testing & System Maintenance
o Hydrostatic testing, pressure testing, and air testing
o Flushing procedures, chlorination, and water quality maintenance
o Flow tests, monitoring, and SCADA basics
,1. What is the minimum depth a water main should be buried in North Carolina to prevent
freezing?
A. 12 inches
B. 18 inches
C. 36 inches
D. 48 inches
Answer: C. 36 inches
Rationale: Water mains in North Carolina are typically installed below the frost line to prevent
freezing, which is generally around 36 inches. Local codes may vary slightly.
2. Which of the following pipe materials is most resistant to corrosion in a sewer system?
A. PVC
B. Ductile iron
C. Concrete
D. Galvanized steel
Answer: A. PVC
Rationale: PVC is chemically inert and highly resistant to corrosion, making it preferred for
sewer applications.
3. According to OSHA, what is the maximum allowable slope for a trench less than 20 feet
deep in stable rock?
A. 1/2:1
B. 1:1
C. 3/4:1
D. 1 1/2:1
Answer: B. 1:1
Rationale: OSHA trenching regulations allow a 1:1 slope for trenches in stable rock under 20
feet deep to ensure worker safety.
,4. When connecting a new water service to an existing main, what is the correct procedure
to minimize contamination?
A. Tap while the main is under full pressure
B. Tap after depressurizing and disinfecting the connection
C. Tap at night to reduce water usage
D. Tap using a high-speed drill without isolation
Answer: B. Tap after depressurizing and disinfecting the connection
Rationale: Depressurizing and disinfecting prevents contamination of the main and ensures
public safety.
5. Which type of valve is typically used for isolating water mains?
A. Butterfly valve
B. Gate valve
C. Check valve
D. Pressure relief valve
Answer: B. Gate valve
Rationale: Gate valves are commonly used for isolating sections of water mains because they
provide full flow when open and tight closure when closed.
6. The minimum separation between a water main and a sewer main should be:
A. 6 inches
B. 10 feet
C. 18 inches horizontally
D. 3 feet vertically
Answer: C. 18 inches horizontally
Rationale: NC plumbing and public utility standards typically require a minimum horizontal
separation of 18 inches to prevent contamination.
7. What is the standard slope for a gravity sewer line to ensure proper flow?
A. 0.1%
B. 0.5%–1%
C. 2%–5%
D. 10%
, Answer: B. 0.5%–1%
Rationale: Gravity sewers need a slope of about 0.5%–1% to maintain self-cleansing velocity
and avoid blockages.
8. When installing a manhole on a sewer line, the minimum distance from the nearest pipe
joint should be:
A. 1 foot
B. 2 feet
C. 3 feet
D. 5 feet
Answer: C. 3 feet
Rationale: Installing a manhole at least 3 feet from the nearest joint ensures proper structural
support and prevents leakage.
9. Which of the following is a primary consideration when selecting trench shoring
methods?
A. Cost of materials
B. Soil type and depth of excavation
C. Number of workers on site
D. Time of year
Answer: B. Soil type and depth of excavation
Rationale: Proper shoring depends on soil stability and trench depth to prevent cave-ins and
comply with OSHA regulations.
10. A contractor notices a discrepancy between the as-built survey and design plans during
construction. What should be done?
A. Continue construction as per original plans
B. Modify the plans without approval
C. Stop work and notify the engineer or authority
D. Make temporary adjustments in the field
Answer: C. Stop work and notify the engineer or authority
Rationale: Any discrepancies must be reviewed and approved by the engineer to prevent errors
or code violations.
Actual Question Comprehensive Practice Exam
with Verified Answers and Detailed Rationales
(2025/2026 Edition)|PDF
Overview:
This Real exam is specifically designed for contractors preparing for the North Carolina Public
Utilities (PU) licensing exam. It contains 300 realistic, multiple-choice questions covering all
critical topics necessary for exam success, including:
Key Topics Covered:
1. Water Distribution Systems
o Water main installation, jointing methods, and pipe materials
o Valves (gate, check, globe, pressure-reducing)
o Fire hydrants, blow-offs, and pressure testing
o Thrust blocks, deadman anchors, and air release valves
o Hydraulic grade line and pressure calculations
2. Sewer Collection Systems
o Gravity and force main design
o Slope requirements and self-cleansing velocity
o Manholes, cleanouts, and drop connections
o Sewer force mains and lift stations
o PVC, ductile iron, and concrete pipe materials
3. Stormwater Management & BMPs
o Infiltration basins, swales, and erosion control
o Environmental compliance and best management practices
4. Backflow Prevention & Cross-Connection Control
o Check valves, double check assemblies, and RPZ devices
o Prevention of contamination in potable water systems
5. Construction Safety & Regulations
o Trench safety (shoring, sloping, protective systems)
o OSHA requirements and utility safety
o Call Before You Dig (811) procedures
6. Testing & System Maintenance
o Hydrostatic testing, pressure testing, and air testing
o Flushing procedures, chlorination, and water quality maintenance
o Flow tests, monitoring, and SCADA basics
,1. What is the minimum depth a water main should be buried in North Carolina to prevent
freezing?
A. 12 inches
B. 18 inches
C. 36 inches
D. 48 inches
Answer: C. 36 inches
Rationale: Water mains in North Carolina are typically installed below the frost line to prevent
freezing, which is generally around 36 inches. Local codes may vary slightly.
2. Which of the following pipe materials is most resistant to corrosion in a sewer system?
A. PVC
B. Ductile iron
C. Concrete
D. Galvanized steel
Answer: A. PVC
Rationale: PVC is chemically inert and highly resistant to corrosion, making it preferred for
sewer applications.
3. According to OSHA, what is the maximum allowable slope for a trench less than 20 feet
deep in stable rock?
A. 1/2:1
B. 1:1
C. 3/4:1
D. 1 1/2:1
Answer: B. 1:1
Rationale: OSHA trenching regulations allow a 1:1 slope for trenches in stable rock under 20
feet deep to ensure worker safety.
,4. When connecting a new water service to an existing main, what is the correct procedure
to minimize contamination?
A. Tap while the main is under full pressure
B. Tap after depressurizing and disinfecting the connection
C. Tap at night to reduce water usage
D. Tap using a high-speed drill without isolation
Answer: B. Tap after depressurizing and disinfecting the connection
Rationale: Depressurizing and disinfecting prevents contamination of the main and ensures
public safety.
5. Which type of valve is typically used for isolating water mains?
A. Butterfly valve
B. Gate valve
C. Check valve
D. Pressure relief valve
Answer: B. Gate valve
Rationale: Gate valves are commonly used for isolating sections of water mains because they
provide full flow when open and tight closure when closed.
6. The minimum separation between a water main and a sewer main should be:
A. 6 inches
B. 10 feet
C. 18 inches horizontally
D. 3 feet vertically
Answer: C. 18 inches horizontally
Rationale: NC plumbing and public utility standards typically require a minimum horizontal
separation of 18 inches to prevent contamination.
7. What is the standard slope for a gravity sewer line to ensure proper flow?
A. 0.1%
B. 0.5%–1%
C. 2%–5%
D. 10%
, Answer: B. 0.5%–1%
Rationale: Gravity sewers need a slope of about 0.5%–1% to maintain self-cleansing velocity
and avoid blockages.
8. When installing a manhole on a sewer line, the minimum distance from the nearest pipe
joint should be:
A. 1 foot
B. 2 feet
C. 3 feet
D. 5 feet
Answer: C. 3 feet
Rationale: Installing a manhole at least 3 feet from the nearest joint ensures proper structural
support and prevents leakage.
9. Which of the following is a primary consideration when selecting trench shoring
methods?
A. Cost of materials
B. Soil type and depth of excavation
C. Number of workers on site
D. Time of year
Answer: B. Soil type and depth of excavation
Rationale: Proper shoring depends on soil stability and trench depth to prevent cave-ins and
comply with OSHA regulations.
10. A contractor notices a discrepancy between the as-built survey and design plans during
construction. What should be done?
A. Continue construction as per original plans
B. Modify the plans without approval
C. Stop work and notify the engineer or authority
D. Make temporary adjustments in the field
Answer: C. Stop work and notify the engineer or authority
Rationale: Any discrepancies must be reviewed and approved by the engineer to prevent errors
or code violations.
