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North Carolina Irrigation Contractor Exam
Questions and Correct Answers with
EXPLANATIONS LATEST THIS YEAR
Summarized Exam Coverage — NC Irrigation Contractor
The NC Irrigation Contractor exam consists of three sections: Water Efficiency/Conservation (50
questions, 70% passing), Irrigation Contracting/Construction (60 questions, 70% passing), and Basic
Business Skills (40 questions, 70% passing) . Topics include: hydraulics, precipitation rate,
evapotranspiration (ET), soil water holding capacity, drip/micro-irrigation, backflow prevention (RPZ,
PVB, DCVA), low-voltage wiring (NEC), trenching safety (OSHA), rain/freeze sensors, cycle-and-soak,
distribution uniformity (DU), pressure-compensating emitters, friction loss (Hazen-Williams),
static/dynamic pressure, controller programming, pump operation, 811 utility locate, NC licensing laws
(Chapter 89G), surety bond ($10,000 required), continuing education (10 hours/year), exemptions, and
business math (profit margins, estimating, job costing) .
1. A homeowner requests an irrigation system for a 0.5-acre lot with clay soil. The sprinkler heads you
select have a precipitation rate higher than the soil's infiltration rate. What is the most likely
consequence?
A) Deep percolation beyond root zone
B) Surface runoff and ponding
C) Even water distribution
D) Reduced evaporation losses
Answer: B
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Rationale: When precipitation rate exceeds infiltration rate, water cannot enter soil fast enough, causing
runoff and ponding .
2. You are calculating the precipitation rate for a zone with four quarter-circle rotors, each discharging
2.0 GPM, spaced 40 feet apart in a square pattern. What is the precipitation rate in inches per hour?
A) 0.48 inches/hour
B) 0.96 inches/hour
C) 1.20 inches/hour
D) 1.44 inches/hour
Answer: A
*Rationale: PR = (96.25 × total GPM) / area; area = 40×40 = 1600 sq ft; total GPM = 4 × 2.0 × 0.25?
Wait—quarter-circle heads cover 1/4 of full, but formula uses actual discharge: each head 2.0 GPM × 4
heads = 8 GPM; (96.25×8)/1600 = 770/1600 = 0.48 in/hr.*
3. You are designing a drip irrigation system for a vegetable garden. The soil is sandy loam. What is the
most appropriate emitter flow rate and spacing?
A) 2.0 GPH every 24 inches
B) 0.5 GPH every 12 inches
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C) 1.0 GPH every 18 inches
D) 4.0 GPH every 36 inches
Answer: B
*Rationale: Sandy loam requires closely spaced, low-flow emitters (0.5-1.0 GPH every 12-18 inches) to
create a continuous wetting pattern .*
4. A commercial property has a backflow preventer that must be tested annually. Which device provides
the highest level of protection against back siphonage and back pressure?
A) Atmospheric Vacuum Breaker (AVB)
B) Pressure Vacuum Breaker (PVB)
C) Double Check Valve Assembly (DCVA)
D) Reduced Pressure Zone (RPZ) assembly
Answer: D
Rationale: RPZ provides highest protection, suitable for high-hazard applications (chemical injection,
fertilizers). It contains two check valves with a relief valve that discharges if pressure differential occurs .
5. You are installing a mainline pipe that will run 400 feet from the point of connection to the first valve.
Flow rate is 40 GPM. Using 2-inch Class 200 PVC (C=150), what is the approximate friction loss using the
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Hazen-Williams formula?
A) 4.2 psi
B) 8.4 psi
C) 12.6 psi
D) 16.8 psi
Answer: B
*Rationale: HL = (10.5 × Q^1.85 × L) / (C^1.85 × d^4.87). For 40 GPM, 2″ pipe, loss ~2.1 psi/100 ft; 400 ft
= 8.4 psi total .*
6. A customer complains that their irrigation system continues running during a rainstorm even though
they have a rain sensor. What is the most likely cause?
A) Rain sensor is wired in series with the common wire and is bypassed
B) Rain sensor is wired in parallel with the valve solenoid
C) Controller is set to "off" position
D) Rain sensor battery is low
Answer: A
North Carolina Irrigation Contractor Exam
Questions and Correct Answers with
EXPLANATIONS LATEST THIS YEAR
Summarized Exam Coverage — NC Irrigation Contractor
The NC Irrigation Contractor exam consists of three sections: Water Efficiency/Conservation (50
questions, 70% passing), Irrigation Contracting/Construction (60 questions, 70% passing), and Basic
Business Skills (40 questions, 70% passing) . Topics include: hydraulics, precipitation rate,
evapotranspiration (ET), soil water holding capacity, drip/micro-irrigation, backflow prevention (RPZ,
PVB, DCVA), low-voltage wiring (NEC), trenching safety (OSHA), rain/freeze sensors, cycle-and-soak,
distribution uniformity (DU), pressure-compensating emitters, friction loss (Hazen-Williams),
static/dynamic pressure, controller programming, pump operation, 811 utility locate, NC licensing laws
(Chapter 89G), surety bond ($10,000 required), continuing education (10 hours/year), exemptions, and
business math (profit margins, estimating, job costing) .
1. A homeowner requests an irrigation system for a 0.5-acre lot with clay soil. The sprinkler heads you
select have a precipitation rate higher than the soil's infiltration rate. What is the most likely
consequence?
A) Deep percolation beyond root zone
B) Surface runoff and ponding
C) Even water distribution
D) Reduced evaporation losses
Answer: B
, Page 2 of 174
Rationale: When precipitation rate exceeds infiltration rate, water cannot enter soil fast enough, causing
runoff and ponding .
2. You are calculating the precipitation rate for a zone with four quarter-circle rotors, each discharging
2.0 GPM, spaced 40 feet apart in a square pattern. What is the precipitation rate in inches per hour?
A) 0.48 inches/hour
B) 0.96 inches/hour
C) 1.20 inches/hour
D) 1.44 inches/hour
Answer: A
*Rationale: PR = (96.25 × total GPM) / area; area = 40×40 = 1600 sq ft; total GPM = 4 × 2.0 × 0.25?
Wait—quarter-circle heads cover 1/4 of full, but formula uses actual discharge: each head 2.0 GPM × 4
heads = 8 GPM; (96.25×8)/1600 = 770/1600 = 0.48 in/hr.*
3. You are designing a drip irrigation system for a vegetable garden. The soil is sandy loam. What is the
most appropriate emitter flow rate and spacing?
A) 2.0 GPH every 24 inches
B) 0.5 GPH every 12 inches
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C) 1.0 GPH every 18 inches
D) 4.0 GPH every 36 inches
Answer: B
*Rationale: Sandy loam requires closely spaced, low-flow emitters (0.5-1.0 GPH every 12-18 inches) to
create a continuous wetting pattern .*
4. A commercial property has a backflow preventer that must be tested annually. Which device provides
the highest level of protection against back siphonage and back pressure?
A) Atmospheric Vacuum Breaker (AVB)
B) Pressure Vacuum Breaker (PVB)
C) Double Check Valve Assembly (DCVA)
D) Reduced Pressure Zone (RPZ) assembly
Answer: D
Rationale: RPZ provides highest protection, suitable for high-hazard applications (chemical injection,
fertilizers). It contains two check valves with a relief valve that discharges if pressure differential occurs .
5. You are installing a mainline pipe that will run 400 feet from the point of connection to the first valve.
Flow rate is 40 GPM. Using 2-inch Class 200 PVC (C=150), what is the approximate friction loss using the
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Hazen-Williams formula?
A) 4.2 psi
B) 8.4 psi
C) 12.6 psi
D) 16.8 psi
Answer: B
*Rationale: HL = (10.5 × Q^1.85 × L) / (C^1.85 × d^4.87). For 40 GPM, 2″ pipe, loss ~2.1 psi/100 ft; 400 ft
= 8.4 psi total .*
6. A customer complains that their irrigation system continues running during a rainstorm even though
they have a rain sensor. What is the most likely cause?
A) Rain sensor is wired in series with the common wire and is bypassed
B) Rain sensor is wired in parallel with the valve solenoid
C) Controller is set to "off" position
D) Rain sensor battery is low
Answer: A
