AR PL Plumbing Contractor Exam
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. The minimum slope for a 3-inch horizontal drainage pipe is:
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 3/4 inch per foot
Rationale: 1/4 inch per foot ensures adequate flow velocity to prevent solids
from settling.
2. The purpose of a trap in a plumbing fixture is to:
A. Increase water pressure
B. Trap debris before entering the sewer
C. Prevent sewer gas from entering the building
D. Reduce pipe corrosion
Rationale: The water seal in a trap blocks sewer gases from entering
occupied spaces.
3. A vent pipe must terminate at least how many feet above a roof surface?
A. 3 ft
B. 6 in
C. 12 in
D. 18 in
Rationale: Code requires terminations at least 6 inches above the roof to
prevent blockage by snow/debris.
,4. The minimum size for a building sewer serving a single-family dwelling is:
A. 2 inches
B. 4 inches
C. 3 inches
D. 6 inches
Rationale: Standard code minimum for building sewers is 4 inches to
ensure capacity.
5. A water heater temperature & pressure relief valve must be piped:
A. Upward
B. Horizontally
C. Downward to within 6 inches of the floor
D. Into a drain trap
Rationale: Discharge must be directed downward to prevent scalding and
terminate safely.
6. The maximum distance between cleanouts in a horizontal drain line is:
A. 25 ft
B. 50 ft
C. 100 ft
D. 150 ft
Rationale: Most plumbing codes require cleanouts every 100 feet for
accessibility.
7. Which backflow prevention device provides the highest level of
protection?
A. Dual-check valve
B. Vacuum breaker
C. Double-check assembly
D. Reduced pressure (RP) assembly
Rationale: The RP assembly provides protection against high hazard
backflow.
8. Copper tubing type suitable for underground installation is:
A. Type M
B. Type AA
C. Type K
, D. Type L
Rationale: Type K has the thickest wall, making it appropriate for burial.
9. A plumbing vent's main function is to:
A. Add oxygen to drainage
B. Increase water flow
C. Prevent siphonage of traps
D. Filter sewer gases
Rationale: Vents equalize pressure to prevent trap seal loss.
10. The minimum burial depth for water service piping in cold climates is
based on:
A. Soil type
B. Frost line depth
C. Pipe material
D. Water pressure
Rationale: Water piping must be buried below frost depth to prevent
freezing.
11. The maximum allowed water temperature in a public handwashing sink
is:
A. 140°F
B. 160°F
C. 110°F
D. 180°F
Rationale: Anti-scald regulations limit public lavatory temperatures to
110°F.
12. A wet vent is defined as a vent that also serves as:
A. A trap seal
B. A drain for another fixture
C. A cleanout point
D. A supply air vent
Rationale: Wet vents carry both drainage and ventilation for designated
fixtures.
13. Minimum size of a trap for a standard residential sink is:
A. 1 inch
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. The minimum slope for a 3-inch horizontal drainage pipe is:
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 3/4 inch per foot
Rationale: 1/4 inch per foot ensures adequate flow velocity to prevent solids
from settling.
2. The purpose of a trap in a plumbing fixture is to:
A. Increase water pressure
B. Trap debris before entering the sewer
C. Prevent sewer gas from entering the building
D. Reduce pipe corrosion
Rationale: The water seal in a trap blocks sewer gases from entering
occupied spaces.
3. A vent pipe must terminate at least how many feet above a roof surface?
A. 3 ft
B. 6 in
C. 12 in
D. 18 in
Rationale: Code requires terminations at least 6 inches above the roof to
prevent blockage by snow/debris.
,4. The minimum size for a building sewer serving a single-family dwelling is:
A. 2 inches
B. 4 inches
C. 3 inches
D. 6 inches
Rationale: Standard code minimum for building sewers is 4 inches to
ensure capacity.
5. A water heater temperature & pressure relief valve must be piped:
A. Upward
B. Horizontally
C. Downward to within 6 inches of the floor
D. Into a drain trap
Rationale: Discharge must be directed downward to prevent scalding and
terminate safely.
6. The maximum distance between cleanouts in a horizontal drain line is:
A. 25 ft
B. 50 ft
C. 100 ft
D. 150 ft
Rationale: Most plumbing codes require cleanouts every 100 feet for
accessibility.
7. Which backflow prevention device provides the highest level of
protection?
A. Dual-check valve
B. Vacuum breaker
C. Double-check assembly
D. Reduced pressure (RP) assembly
Rationale: The RP assembly provides protection against high hazard
backflow.
8. Copper tubing type suitable for underground installation is:
A. Type M
B. Type AA
C. Type K
, D. Type L
Rationale: Type K has the thickest wall, making it appropriate for burial.
9. A plumbing vent's main function is to:
A. Add oxygen to drainage
B. Increase water flow
C. Prevent siphonage of traps
D. Filter sewer gases
Rationale: Vents equalize pressure to prevent trap seal loss.
10. The minimum burial depth for water service piping in cold climates is
based on:
A. Soil type
B. Frost line depth
C. Pipe material
D. Water pressure
Rationale: Water piping must be buried below frost depth to prevent
freezing.
11. The maximum allowed water temperature in a public handwashing sink
is:
A. 140°F
B. 160°F
C. 110°F
D. 180°F
Rationale: Anti-scald regulations limit public lavatory temperatures to
110°F.
12. A wet vent is defined as a vent that also serves as:
A. A trap seal
B. A drain for another fixture
C. A cleanout point
D. A supply air vent
Rationale: Wet vents carry both drainage and ventilation for designated
fixtures.
13. Minimum size of a trap for a standard residential sink is:
A. 1 inch
