Arizona (AZ) CR37 / C37 Plumbing Practice Exam 200 Practice
Questions and Answers
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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
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 .
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
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
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 many plumbing installations?
A) PVC
B) ABS
C) Cast iron
D) Copper
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
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
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
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
B) Double check valve assembly (DCVA)
C) Reduced pressure zone (RPZ) valve
D) Atmospheric vacuum breaker (AVB)
Answer: C) Reduced pressure zone (RPZ) valve
Questions and Answers
---
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
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 .
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
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
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 many plumbing installations?
A) PVC
B) ABS
C) Cast iron
D) Copper
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
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
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
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
B) Double check valve assembly (DCVA)
C) Reduced pressure zone (RPZ) valve
D) Atmospheric vacuum breaker (AVB)
Answer: C) Reduced pressure zone (RPZ) valve
