AR PL Plumbing Contractor Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2027
Q&A | Instant Download Pdf
Q1. What is the primary purpose of a plumbing trap?
A. Increase water pressure
B. Prevent sewer gases from entering a building
C. Increase drainage flow
D. Reduce pipe diameter
Answer: B. Prevent sewer gases from entering a building
Rationale: A properly installed trap maintains a water seal that prevents
sewer gases and odors from entering occupied spaces while allowing
wastewater to drain.
Q2. Which fitting is commonly used to change the direction of a drainage
pipe by 90 degrees while maintaining relatively smooth flow?
,A. Sanitary tee
B. Wye
C. Long-sweep elbow
D. Straight coupling
Answer: C. Long-sweep elbow
Rationale: A long-sweep elbow provides a gradual change in direction,
reducing turbulence and the likelihood of blockage in drainage piping.
Q3. What is the main function of a plumbing vent system?
A. Supply drinking water
B. Increase water temperature
C. Protect trap seals and allow proper drainage flow
D. Store wastewater
Answer: C. Protect trap seals and allow proper drainage flow
Rationale: Venting equalizes pressure in the drainage system and helps
prevent siphonage or backpressure that could compromise trap seals.
Q4. Which pipe material is commonly used for cold-water distribution
systems?
A. PVC
B. Cast iron soil pipe
,C. Clay tile
D. Vitrified brick
Answer: A. PVC
Rationale: PVC is widely used for cold-water distribution where permitted
because it is corrosion-resistant, lightweight, and relatively easy to install.
Q5. What does a water hammer arrestor control?
A. Sewer gas
B. Thermal expansion
C. Sudden pressure surges caused by flowing water stopping abruptly
D. Low water temperature
Answer: C. Sudden pressure surges caused by flowing water stopping
abruptly
Rationale: Water hammer occurs when moving water is stopped suddenly.
An arrestor provides an air or gas cushion that absorbs the pressure surge.
Q6. Which device is designed to prevent contaminated water from flowing
backward into a potable water supply?
A. Pressure gauge
B. Backflow prevention device
, C. Cleanout
D. Trap primer
Answer: B. Backflow prevention device
Rationale: Backflow prevention devices protect potable water systems
from contamination caused by backpressure or backsiphonage.
Q7. What is the purpose of a plumbing cleanout?
A. Increase water temperature
B. Provide access for cleaning and clearing drainage piping
C. Reduce water pressure
D. Prevent pipe expansion
Answer: B. Provide access for cleaning and clearing drainage piping
Rationale: Cleanouts provide accessible openings through which drain lines
can be inspected, rodded, or otherwise cleared of obstructions.
Q8. Which fitting is generally preferred for connecting a branch drain to a
horizontal drainage pipe?
A. Wye
B. Cap
C. Coupling
D. Reducing bushing
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2027
Q&A | Instant Download Pdf
Q1. What is the primary purpose of a plumbing trap?
A. Increase water pressure
B. Prevent sewer gases from entering a building
C. Increase drainage flow
D. Reduce pipe diameter
Answer: B. Prevent sewer gases from entering a building
Rationale: A properly installed trap maintains a water seal that prevents
sewer gases and odors from entering occupied spaces while allowing
wastewater to drain.
Q2. Which fitting is commonly used to change the direction of a drainage
pipe by 90 degrees while maintaining relatively smooth flow?
,A. Sanitary tee
B. Wye
C. Long-sweep elbow
D. Straight coupling
Answer: C. Long-sweep elbow
Rationale: A long-sweep elbow provides a gradual change in direction,
reducing turbulence and the likelihood of blockage in drainage piping.
Q3. What is the main function of a plumbing vent system?
A. Supply drinking water
B. Increase water temperature
C. Protect trap seals and allow proper drainage flow
D. Store wastewater
Answer: C. Protect trap seals and allow proper drainage flow
Rationale: Venting equalizes pressure in the drainage system and helps
prevent siphonage or backpressure that could compromise trap seals.
Q4. Which pipe material is commonly used for cold-water distribution
systems?
A. PVC
B. Cast iron soil pipe
,C. Clay tile
D. Vitrified brick
Answer: A. PVC
Rationale: PVC is widely used for cold-water distribution where permitted
because it is corrosion-resistant, lightweight, and relatively easy to install.
Q5. What does a water hammer arrestor control?
A. Sewer gas
B. Thermal expansion
C. Sudden pressure surges caused by flowing water stopping abruptly
D. Low water temperature
Answer: C. Sudden pressure surges caused by flowing water stopping
abruptly
Rationale: Water hammer occurs when moving water is stopped suddenly.
An arrestor provides an air or gas cushion that absorbs the pressure surge.
Q6. Which device is designed to prevent contaminated water from flowing
backward into a potable water supply?
A. Pressure gauge
B. Backflow prevention device
, C. Cleanout
D. Trap primer
Answer: B. Backflow prevention device
Rationale: Backflow prevention devices protect potable water systems
from contamination caused by backpressure or backsiphonage.
Q7. What is the purpose of a plumbing cleanout?
A. Increase water temperature
B. Provide access for cleaning and clearing drainage piping
C. Reduce water pressure
D. Prevent pipe expansion
Answer: B. Provide access for cleaning and clearing drainage piping
Rationale: Cleanouts provide accessible openings through which drain lines
can be inspected, rodded, or otherwise cleared of obstructions.
Q8. Which fitting is generally preferred for connecting a branch drain to a
horizontal drainage pipe?
A. Wye
B. Cap
C. Coupling
D. Reducing bushing
