PLUMBING CONTRACTOR LICENSE EXAM LATEST 2026 UPDATE
FAST REVIWED FROM ACTUAL TEST 150 QUESTIONS AND 100%
VERIFIED ANSWERS| A+ GRADE Q&A | INSTANT DOWNLOAD PDF
1. What is the primary purpose of a vent system in plumbing?
A. Increase water pressure
B. Prevent siphoning of traps
C. Heat water faster
D. Store wastewater
B. Prevent siphoning of traps
Vent systems allow air into the plumbing system to maintain trap seals and prevent sewer
gases from entering buildings.
2. Which pipe is commonly used for water distribution in modern plumbing?
A. Cast iron
B. Copper
C. Clay
D. Lead
B. Copper
Copper is durable, corrosion-resistant, and widely used for potable water systems.
3. What is the minimum slope for a 4-inch horizontal drain pipe?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. No slope required
A. 1/8 inch per foot
Larger pipes require less slope while still maintaining proper flow.
4. What device prevents backflow in a plumbing system?
A. Trap
B. Valve
C. Backflow preventer
D. Vent
C. Backflow preventer
It ensures contaminated water does not reverse into clean water supply.
5. Which fitting changes pipe direction 90 degrees?
A. Tee
B. Coupling
C. Elbow
D. Union
C. Elbow
Elbows are used to change direction in piping systems.
6. What is the function of a trap?
A. Increase flow speed
B. Prevent gas entry
C. Store water
D. Filter debris
, B. Prevent gas entry
Traps hold water to block sewer gases from entering buildings.
7. Which material is NOT typically used for water supply lines?
A. PVC
B. Copper
C. PEX
D. Lead
D. Lead
Lead is toxic and no longer used for potable water systems.
8. What is the standard pipe thread used in plumbing in the US system?
A. BSP
B. NPT
C. Metric thread
D. SAE
B. NPT
National Pipe Thread (NPT) is the standard in the US.
9. What does DWV stand for?
A. Drain Waste Vent
B. Domestic Water Valve
C. Drain Water Volume
D. Direct Water Ventilation
A. Drain Waste Vent
DWV systems remove waste and allow ventilation.
10. What is the main purpose of a cleanout?
A. Increase pressure
B. Access for pipe cleaning
C. Control water temperature
D. Filter water
B. Access for pipe cleaning
Cleanouts allow maintenance access to drain lines.
11. Which tool is used to cut copper pipe?
A. Hacksaw
B. Pipe cutter
C. Chisel
D. Hammer
B. Pipe cutter
Pipe cutters provide clean, precise cuts.
12. What causes water hammer?
A. High temperature
B. Sudden valve closure
C. Low pressure
D. Dirty water
B. Sudden valve closure
Rapid stopping of water flow causes pressure shock.
13. What is the purpose of a pressure regulator?
A. Increase pipe size
, B. Control water pressure
C. Heat water
D. Filter debris
B. Control water pressure
It reduces incoming pressure to safe levels.
14. Which pipe is flexible and commonly used for hot and cold water?
A. Steel
B. PEX
C. Clay
D. Cast iron
B. PEX
PEX is flexible and easy to install.
15. What is the minimum size of a building sewer line in most codes?
A. 2 inches
B. 3 inches
C. 4 inches
D. 6 inches
C. 4 inches
Most codes require at least 4-inch sewer lines.
16. What is the function of a vent stack?
A. Carry waste
B. Provide air circulation
C. Increase pressure
D. Store water
B. Provide air circulation
Vent stacks maintain neutral air pressure.
17. Which fixture requires the largest trap size?
A. Sink
B. Toilet
C. Shower
D. Urinal
B. Toilet
Toilets handle larger waste volumes.
18. What does PSI measure?
A. Pipe size
B. Water pressure
C. Flow rate
D. Temperature
B. Water pressure
PSI stands for pounds per square inch.
19. Which valve allows flow in only one direction?
A. Gate valve
B. Ball valve
C. Check valve
D. Globe valve
FAST REVIWED FROM ACTUAL TEST 150 QUESTIONS AND 100%
VERIFIED ANSWERS| A+ GRADE Q&A | INSTANT DOWNLOAD PDF
1. What is the primary purpose of a vent system in plumbing?
A. Increase water pressure
B. Prevent siphoning of traps
C. Heat water faster
D. Store wastewater
B. Prevent siphoning of traps
Vent systems allow air into the plumbing system to maintain trap seals and prevent sewer
gases from entering buildings.
2. Which pipe is commonly used for water distribution in modern plumbing?
A. Cast iron
B. Copper
C. Clay
D. Lead
B. Copper
Copper is durable, corrosion-resistant, and widely used for potable water systems.
3. What is the minimum slope for a 4-inch horizontal drain pipe?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. No slope required
A. 1/8 inch per foot
Larger pipes require less slope while still maintaining proper flow.
4. What device prevents backflow in a plumbing system?
A. Trap
B. Valve
C. Backflow preventer
D. Vent
C. Backflow preventer
It ensures contaminated water does not reverse into clean water supply.
5. Which fitting changes pipe direction 90 degrees?
A. Tee
B. Coupling
C. Elbow
D. Union
C. Elbow
Elbows are used to change direction in piping systems.
6. What is the function of a trap?
A. Increase flow speed
B. Prevent gas entry
C. Store water
D. Filter debris
, B. Prevent gas entry
Traps hold water to block sewer gases from entering buildings.
7. Which material is NOT typically used for water supply lines?
A. PVC
B. Copper
C. PEX
D. Lead
D. Lead
Lead is toxic and no longer used for potable water systems.
8. What is the standard pipe thread used in plumbing in the US system?
A. BSP
B. NPT
C. Metric thread
D. SAE
B. NPT
National Pipe Thread (NPT) is the standard in the US.
9. What does DWV stand for?
A. Drain Waste Vent
B. Domestic Water Valve
C. Drain Water Volume
D. Direct Water Ventilation
A. Drain Waste Vent
DWV systems remove waste and allow ventilation.
10. What is the main purpose of a cleanout?
A. Increase pressure
B. Access for pipe cleaning
C. Control water temperature
D. Filter water
B. Access for pipe cleaning
Cleanouts allow maintenance access to drain lines.
11. Which tool is used to cut copper pipe?
A. Hacksaw
B. Pipe cutter
C. Chisel
D. Hammer
B. Pipe cutter
Pipe cutters provide clean, precise cuts.
12. What causes water hammer?
A. High temperature
B. Sudden valve closure
C. Low pressure
D. Dirty water
B. Sudden valve closure
Rapid stopping of water flow causes pressure shock.
13. What is the purpose of a pressure regulator?
A. Increase pipe size
, B. Control water pressure
C. Heat water
D. Filter debris
B. Control water pressure
It reduces incoming pressure to safe levels.
14. Which pipe is flexible and commonly used for hot and cold water?
A. Steel
B. PEX
C. Clay
D. Cast iron
B. PEX
PEX is flexible and easy to install.
15. What is the minimum size of a building sewer line in most codes?
A. 2 inches
B. 3 inches
C. 4 inches
D. 6 inches
C. 4 inches
Most codes require at least 4-inch sewer lines.
16. What is the function of a vent stack?
A. Carry waste
B. Provide air circulation
C. Increase pressure
D. Store water
B. Provide air circulation
Vent stacks maintain neutral air pressure.
17. Which fixture requires the largest trap size?
A. Sink
B. Toilet
C. Shower
D. Urinal
B. Toilet
Toilets handle larger waste volumes.
18. What does PSI measure?
A. Pipe size
B. Water pressure
C. Flow rate
D. Temperature
B. Water pressure
PSI stands for pounds per square inch.
19. Which valve allows flow in only one direction?
A. Gate valve
B. Ball valve
C. Check valve
D. Globe valve
