ALABAMA PLUMBING CONTRACTOR
LICENSING EXAM —QUESTIONS AND
CORRECT DETAILED ANSWERS LATEST 2026
1. What plumbing code is currently identified by the Alabama
Plumbers & Gas Fitters Examining Board as the code used for
examination applicants?
A. 2018 International Plumbing Code
B. 2021 International Plumbing Code
C. 2024 International Plumbing Code
D. 2021 Uniform Plumbing Code
Correct Answer: B. 2021 International Plumbing Code
Rationale: The Alabama Board states that applicants are
tested on the 2021 International Plumbing Code.
2. What is the primary purpose of a plumbing vent system?
A. Increase water pressure
,B. Remove sediment from water
C. Protect trap seals and allow proper drainage airflow
D. Heat the drainage system
Correct Answer: C. Protect trap seals and allow proper
drainage airflow
Rationale: Venting permits air movement through the drainage
system and protects trap seals from siphonage and
backpressure.
3. What is the primary function of a plumbing trap?
A. Increase water flow
B. Prevent sewer gases from entering occupied spaces
C. Filter drinking water
D. Reduce water temperature
Correct Answer: B. Prevent sewer gases from entering
occupied spaces
Rationale: The water seal in a trap prevents sewer gases from
entering the building through the fixture drain.
,4. Which fixture normally requires a trap?
A. Water heater
B. Lavatory
C. Hose bibb
D. Water meter
Correct Answer: B. Lavatory
Rationale: Plumbing fixtures that discharge into the drainage
system generally require an approved trap.
5. What is a P-trap designed to maintain?
A. Water pressure
B. A water seal
C. Gas pressure
D. Pipe temperature
Correct Answer: B. A water seal
Rationale: The retained water in the trap blocks sewer gases
from entering the building.
, 6. What condition can cause a trap seal to be siphoned away?
A. Proper venting
B. Excessive negative pressure in the drainage system
C. Low water temperature
D. Oversized supply piping
Correct Answer: B. Excessive negative pressure in the
drainage system
Rationale: Negative pressure can siphon water out of a trap
unless the drainage system is properly vented.
7. What is backflow?
A. Normal downstream water movement
B. Reverse flow of water or other substances into the potable
water supply
C. Water flowing through a vent
D. Wastewater entering a trap
Correct Answer: B. Reverse flow of water or other
substances into the potable water supply
LICENSING EXAM —QUESTIONS AND
CORRECT DETAILED ANSWERS LATEST 2026
1. What plumbing code is currently identified by the Alabama
Plumbers & Gas Fitters Examining Board as the code used for
examination applicants?
A. 2018 International Plumbing Code
B. 2021 International Plumbing Code
C. 2024 International Plumbing Code
D. 2021 Uniform Plumbing Code
Correct Answer: B. 2021 International Plumbing Code
Rationale: The Alabama Board states that applicants are
tested on the 2021 International Plumbing Code.
2. What is the primary purpose of a plumbing vent system?
A. Increase water pressure
,B. Remove sediment from water
C. Protect trap seals and allow proper drainage airflow
D. Heat the drainage system
Correct Answer: C. Protect trap seals and allow proper
drainage airflow
Rationale: Venting permits air movement through the drainage
system and protects trap seals from siphonage and
backpressure.
3. What is the primary function of a plumbing trap?
A. Increase water flow
B. Prevent sewer gases from entering occupied spaces
C. Filter drinking water
D. Reduce water temperature
Correct Answer: B. Prevent sewer gases from entering
occupied spaces
Rationale: The water seal in a trap prevents sewer gases from
entering the building through the fixture drain.
,4. Which fixture normally requires a trap?
A. Water heater
B. Lavatory
C. Hose bibb
D. Water meter
Correct Answer: B. Lavatory
Rationale: Plumbing fixtures that discharge into the drainage
system generally require an approved trap.
5. What is a P-trap designed to maintain?
A. Water pressure
B. A water seal
C. Gas pressure
D. Pipe temperature
Correct Answer: B. A water seal
Rationale: The retained water in the trap blocks sewer gases
from entering the building.
, 6. What condition can cause a trap seal to be siphoned away?
A. Proper venting
B. Excessive negative pressure in the drainage system
C. Low water temperature
D. Oversized supply piping
Correct Answer: B. Excessive negative pressure in the
drainage system
Rationale: Negative pressure can siphon water out of a trap
unless the drainage system is properly vented.
7. What is backflow?
A. Normal downstream water movement
B. Reverse flow of water or other substances into the potable
water supply
C. Water flowing through a vent
D. Wastewater entering a trap
Correct Answer: B. Reverse flow of water or other
substances into the potable water supply
