Arizona (AZ) CR37, C37 Plumbing Practice Exam 200 Practice Questions
and Correct Answers Based on Arizona Registrar of Contractors (ROC)
Exam Blueprint 2026 Edition
Plumbing Systems and Components (Questions 1-50)
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1. What is the primary purpose of a trap in a plumbing fixture?
A) To filter debris from wastewater
B) To prevent sewer gases from entering the building
C) To regulate water flow
D) To reduce water consumption
Correct Answer: B) To prevent sewer gases from entering the building
Explanation: A trap maintains a water seal that blocks sewer gases from entering the building,
ensuring a sanitary, odor-free interior. This is a fundamental principle in all plumbing systems .
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2. Which type of trap is most commonly used under a lavatory sink?
A) S-trap
B) P-trap
C) Drum trap
,D) Bell trap
Correct Answer: B) P-trap
Explanation: P-traps are the standard under sinks because they reliably maintain a water seal,
are easy to clean and maintain, and comply with modern plumbing code requirements .
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3. In a drainage system, what is the purpose of a vent pipe?
A) To carry waste to the sewer
B) To provide a path for heat to escape
C) To filter waste before disposal
D) To allow fresh air into the system to prevent vacuum formation and prevent siphoning of
traps
Correct Answer: D) To allow fresh air into the system to prevent vacuum formation and prevent
siphoning of traps
Explanation: Vent pipes equalize air pressure in drain-waste-vent (DWV) systems, preventing
trap siphonage and allowing wastewater to flow smoothly .
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4. Which material is most suitable for drainage-waste-vent (DWV) piping in heavy-duty
commercial installations?
A) PVC
,B) ABS
C) Cast iron
D) Copper
Correct Answer: C) Cast iron
Explanation: Cast iron is durable, handles heat well, and is commonly used in commercial or
heavy-duty DWV systems—especially where rigidity and fire-resistance matter .
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5. What is the minimum diameter commonly used for a residential bathroom sink (lavatory)
drain line under typical plumbing code?
A) 1 inch
B) 1.25 inches
C) 1.5 inches
D) 2 inches
Correct Answer: C) 1.5 inches
Explanation: A 1.5-inch drain line gives adequate capacity for typical sink waste water flow and
is widely accepted under plumbing codes for lavatories .
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6. What is the function of a cleanout in a drainage system?
A) To prevent backflow of waste into the fixture
, B) To provide access for cleaning and maintaining the drainage system
C) To allow connection of additional fixtures
D) To filter waste before disposal
Correct Answer: B) To provide access for cleaning and maintaining the drainage system
Explanation: Cleanouts provide maintenance access so blockages or buildup can be cleared—
essential for maintaining system function over time .
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7. What is the typical slope required for a horizontal drainage pipe to ensure proper flow?
A) Level / no slope
B) 1/16 inch per foot
C) 1/8 inch per foot
D) 1/2 inch per foot
Correct Answer: C) 1/8 inch per foot
Explanation: A slope of 1/8 inch per foot is generally acceptable for gravity-assisted flow
without excessive velocity or risk of siphoning .
---
8. Which backflow prevention device is commonly used in commercial or industrial applications
with high contamination hazard?
A) Air gap
and Correct Answers Based on Arizona Registrar of Contractors (ROC)
Exam Blueprint 2026 Edition
Plumbing Systems and Components (Questions 1-50)
---
1. What is the primary purpose of a trap in a plumbing fixture?
A) To filter debris from wastewater
B) To prevent sewer gases from entering the building
C) To regulate water flow
D) To reduce water consumption
Correct Answer: B) To prevent sewer gases from entering the building
Explanation: A trap maintains a water seal that blocks sewer gases from entering the building,
ensuring a sanitary, odor-free interior. This is a fundamental principle in all plumbing systems .
---
2. Which type of trap is most commonly used under a lavatory sink?
A) S-trap
B) P-trap
C) Drum trap
,D) Bell trap
Correct Answer: B) P-trap
Explanation: P-traps are the standard under sinks because they reliably maintain a water seal,
are easy to clean and maintain, and comply with modern plumbing code requirements .
---
3. In a drainage system, what is the purpose of a vent pipe?
A) To carry waste to the sewer
B) To provide a path for heat to escape
C) To filter waste before disposal
D) To allow fresh air into the system to prevent vacuum formation and prevent siphoning of
traps
Correct Answer: D) To allow fresh air into the system to prevent vacuum formation and prevent
siphoning of traps
Explanation: Vent pipes equalize air pressure in drain-waste-vent (DWV) systems, preventing
trap siphonage and allowing wastewater to flow smoothly .
---
4. Which material is most suitable for drainage-waste-vent (DWV) piping in heavy-duty
commercial installations?
A) PVC
,B) ABS
C) Cast iron
D) Copper
Correct Answer: C) Cast iron
Explanation: Cast iron is durable, handles heat well, and is commonly used in commercial or
heavy-duty DWV systems—especially where rigidity and fire-resistance matter .
---
5. What is the minimum diameter commonly used for a residential bathroom sink (lavatory)
drain line under typical plumbing code?
A) 1 inch
B) 1.25 inches
C) 1.5 inches
D) 2 inches
Correct Answer: C) 1.5 inches
Explanation: A 1.5-inch drain line gives adequate capacity for typical sink waste water flow and
is widely accepted under plumbing codes for lavatories .
---
6. What is the function of a cleanout in a drainage system?
A) To prevent backflow of waste into the fixture
, B) To provide access for cleaning and maintaining the drainage system
C) To allow connection of additional fixtures
D) To filter waste before disposal
Correct Answer: B) To provide access for cleaning and maintaining the drainage system
Explanation: Cleanouts provide maintenance access so blockages or buildup can be cleared—
essential for maintaining system function over time .
---
7. What is the typical slope required for a horizontal drainage pipe to ensure proper flow?
A) Level / no slope
B) 1/16 inch per foot
C) 1/8 inch per foot
D) 1/2 inch per foot
Correct Answer: C) 1/8 inch per foot
Explanation: A slope of 1/8 inch per foot is generally acceptable for gravity-assisted flow
without excessive velocity or risk of siphoning .
---
8. Which backflow prevention device is commonly used in commercial or industrial applications
with high contamination hazard?
A) Air gap
