AZ ROC – C-37 Plumbing Contractor
Examination (Commercial Plumbing)
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A| Instant
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Question 1
In a commercial plumbing system, what is the primary purpose of a trap
seal?
A. To increase water pressure
B. To prevent sewer gases from entering the building
C. To increase drainage velocity
D. To prevent water hammer
Answer: B. To prevent sewer gases from entering the building
Rationale: A plumbing trap retains a specific amount of water that
forms a seal between the drainage system and the occupied space.
,This water barrier helps prevent sewer gases, odors, and potentially
hazardous contaminants from entering the building.
Question 2
Which component is primarily used to protect a potable water supply
from backsiphonage?
A. Cleanout
B. Backflow prevention assembly
C. P-trap
D. Expansion joint
Answer: B. Backflow prevention assembly
Rationale: Backflow prevention devices protect potable water from
contamination caused by reverse flow. The appropriate device
depends on the degree of hazard and the type of backflow condition
that must be prevented.
Question 3
What is the primary function of a plumbing vent system?
,A. Increase the pressure in the water distribution system
B. Provide additional water to fixtures
C. Protect trap seals and allow drainage systems to operate properly
D. Remove sediment from water heaters
Answer: C. Protect trap seals and allow drainage systems to operate
properly
Rationale: Drainage vents allow air to enter and leave the drainage
piping system. Proper venting helps equalize pressure, protects trap
seals from siphonage or backpressure, and promotes proper drainage.
Question 4
Which fitting is generally used to change the direction of a drainage
pipe?
A. Elbow
B. Coupling
C. Union
D. Adapter
Answer: A. Elbow
, Rationale: Elbows are designed to change the direction of piping. In
drainage systems, fittings must be selected and oriented so that they
provide proper flow and minimize the possibility of blockages.
Question 5
What is the purpose of a cleanout in a commercial drainage system?
A. To regulate water temperature
B. To provide access for inspection and clearing of drainage piping
C. To increase fixture pressure
D. To prevent thermal expansion
Answer: B. To provide access for inspection and clearing of drainage
piping
Rationale: Cleanouts provide accessible openings through which
drainage piping can be inspected, cleaned, or cleared of obstructions.
Commercial systems often require strategically located cleanouts
because of their size and complexity.
Question 6
Examination (Commercial Plumbing)
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A| Instant
Download Pdf
Question 1
In a commercial plumbing system, what is the primary purpose of a trap
seal?
A. To increase water pressure
B. To prevent sewer gases from entering the building
C. To increase drainage velocity
D. To prevent water hammer
Answer: B. To prevent sewer gases from entering the building
Rationale: A plumbing trap retains a specific amount of water that
forms a seal between the drainage system and the occupied space.
,This water barrier helps prevent sewer gases, odors, and potentially
hazardous contaminants from entering the building.
Question 2
Which component is primarily used to protect a potable water supply
from backsiphonage?
A. Cleanout
B. Backflow prevention assembly
C. P-trap
D. Expansion joint
Answer: B. Backflow prevention assembly
Rationale: Backflow prevention devices protect potable water from
contamination caused by reverse flow. The appropriate device
depends on the degree of hazard and the type of backflow condition
that must be prevented.
Question 3
What is the primary function of a plumbing vent system?
,A. Increase the pressure in the water distribution system
B. Provide additional water to fixtures
C. Protect trap seals and allow drainage systems to operate properly
D. Remove sediment from water heaters
Answer: C. Protect trap seals and allow drainage systems to operate
properly
Rationale: Drainage vents allow air to enter and leave the drainage
piping system. Proper venting helps equalize pressure, protects trap
seals from siphonage or backpressure, and promotes proper drainage.
Question 4
Which fitting is generally used to change the direction of a drainage
pipe?
A. Elbow
B. Coupling
C. Union
D. Adapter
Answer: A. Elbow
, Rationale: Elbows are designed to change the direction of piping. In
drainage systems, fittings must be selected and oriented so that they
provide proper flow and minimize the possibility of blockages.
Question 5
What is the purpose of a cleanout in a commercial drainage system?
A. To regulate water temperature
B. To provide access for inspection and clearing of drainage piping
C. To increase fixture pressure
D. To prevent thermal expansion
Answer: B. To provide access for inspection and clearing of drainage
piping
Rationale: Cleanouts provide accessible openings through which
drainage piping can be inspected, cleaned, or cleared of obstructions.
Commercial systems often require strategically located cleanouts
because of their size and complexity.
Question 6
