Louisiana (LA) Plumbing
Contractor Exam Questions
And Correct Answers (Verified
Answers) Plus Rationales 2025
Q&A | Instant Download Pdf
1. What is the minimum slope for a horizontal drain pipe 3
inches or less in diameter?
A. 1/4 inch per foot
B. 1/8 inch per foot
C. 1/2 inch per foot
D. Level
Answer: A
Rationale: Plumbing code requires 1/4 inch per foot slope for
proper drainage and to prevent solids buildup.
2. What is the purpose of a trap in a plumbing system?
A. Increase water pressure
,B. Prevent sewer gases from entering the building
C. Filter debris
D. Increase flow rate
Answer: B
Rationale: Traps hold water to create a seal that blocks sewer
gases.
3. What is the standard vent pipe size minimum for a water
closet?
A. 1 inch
B. 1 1/4 inches
C. 1 1/2 inches
D. 2 inches
Answer: C
Rationale: Minimum vent size for fixtures like toilets is
typically 1 1/2 inches.
4. Which pipe is commonly used for DWV systems today?
A. Copper
,B. Galvanized steel
C. PVC
D. Lead
Answer: C
Rationale: PVC is widely used for DWV due to corrosion
resistance and cost.
5. What is the minimum air gap required for a dishwasher?
A. 1 inch
B. 2 inches
C. Twice the pipe diameter
D. 3 inches
Answer: C
Rationale: Air gap must be at least twice the inlet pipe
diameter for backflow prevention.
6. What does DWV stand for?
A. Drain Waste Vent
, B. Domestic Water Valve
C. Drain Water Vacuum
D. Domestic Waste Valve
Answer: A
Rationale: DWV refers to Drain, Waste, and Vent systems.
7. Which fitting changes the direction of flow by 90 degrees?
A. Tee
B. Wye
C. Elbow
D. Coupling
Answer: C
Rationale: Elbows are used to change direction in piping
systems.
8. What is the function of a cleanout?
A. Increase flow
B. Provide access for clearing blockages
Contractor Exam Questions
And Correct Answers (Verified
Answers) Plus Rationales 2025
Q&A | Instant Download Pdf
1. What is the minimum slope for a horizontal drain pipe 3
inches or less in diameter?
A. 1/4 inch per foot
B. 1/8 inch per foot
C. 1/2 inch per foot
D. Level
Answer: A
Rationale: Plumbing code requires 1/4 inch per foot slope for
proper drainage and to prevent solids buildup.
2. What is the purpose of a trap in a plumbing system?
A. Increase water pressure
,B. Prevent sewer gases from entering the building
C. Filter debris
D. Increase flow rate
Answer: B
Rationale: Traps hold water to create a seal that blocks sewer
gases.
3. What is the standard vent pipe size minimum for a water
closet?
A. 1 inch
B. 1 1/4 inches
C. 1 1/2 inches
D. 2 inches
Answer: C
Rationale: Minimum vent size for fixtures like toilets is
typically 1 1/2 inches.
4. Which pipe is commonly used for DWV systems today?
A. Copper
,B. Galvanized steel
C. PVC
D. Lead
Answer: C
Rationale: PVC is widely used for DWV due to corrosion
resistance and cost.
5. What is the minimum air gap required for a dishwasher?
A. 1 inch
B. 2 inches
C. Twice the pipe diameter
D. 3 inches
Answer: C
Rationale: Air gap must be at least twice the inlet pipe
diameter for backflow prevention.
6. What does DWV stand for?
A. Drain Waste Vent
, B. Domestic Water Valve
C. Drain Water Vacuum
D. Domestic Waste Valve
Answer: A
Rationale: DWV refers to Drain, Waste, and Vent systems.
7. Which fitting changes the direction of flow by 90 degrees?
A. Tee
B. Wye
C. Elbow
D. Coupling
Answer: C
Rationale: Elbows are used to change direction in piping
systems.
8. What is the function of a cleanout?
A. Increase flow
B. Provide access for clearing blockages
