JOURNEYMAN PLUMBER LICENSING
EXAM QUESTIONS AND CORRECT
ANSWERS (VERIFIED ANSWERS) PLUS
RATIONALES 2026 Q&A | INSTANT
DOWNLOAD PDF
1. What is the standard slope for a 4-inch sewer line?
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 is the minimum recommended slope to
maintain self-cleaning velocity and prevent solids deposition.
2. What does “DWV” stand for in plumbing?
A. Drain, Waste, and Vent
B. Domestic Water Valve
C. Direct Water Velocity
D. Drainage Water Volume
Rationale: DWV refers to the system that removes sewage and venting
gases to prevent traps from being siphoned.
3. What material is commonly used for residential cold water supply lines?
A. Cast iron
B. Lead
C. Copper
D. Galvanized steel
, Rationale: Copper tubing (Type L or M) is widely accepted due to
durability and corrosion resistance.
4. Which type of pipe is prohibited for potable water in most jurisdictions?
A. PVC
B. PEX
C. Polybutylene
D. CPVC
Rationale: Polybutylene was banned due to widespread failures and leaks.
5. What device prevents backflow in a plumbing system?
A. Drain cock
B. Pressure reducer
C. Backflow preventer
D. Ball valve
Rationale: Backflow preventers protect potable water from contamination
due to reverse flow.
6. What is the minimum trap arm length before it can turn vertically?
A. 6 inches
B. 2 times pipe diameter
C. 3 feet
D. 12 inches
Rationale: Trap arm must be at least twice the pipe diameter to avoid
siphonage.
7. What is the typical PSI rating for residential water pressure?
A. 30–40 PSI
B. 40–80 PSI
C. 80–100 PSI
D. 100–120 PSI
Rationale: Most residential systems operate between 40–80 PSI for safety
and performance.
, 8. Where must a cleanout be installed on a horizontal drain?
A. At every 20 feet
B. Only at the building entrance
C. At changes of direction >45°
D. Only at the footer
Rationale: Cleanouts allow access for maintenance where blockage is
likely.
9. What is used to join two lengths of copper pipe?
A. Thread compound
B. Compression fitting
C. Soldered fitting
D. PVC cement
Rationale: Copper is commonly joined by soldering with flux to create a
watertight seal.
10.Which gas is dangerous if allowed to accumulate in the plumbing system?
A. Oxygen
B. Nitrogen
C. Hydrogen sulfide
D. Carbon monoxide
Rationale: Hydrogen sulfide in sewer gas is toxic and corrosive.
11.What is the purpose of a vent in plumbing?
A. Increase water pressure
B. Filter impurities
C. Equalize pressure and remove gases
D. Heat waste water
Rationale: Vents prevent traps from siphoning and allow sewer gas to
escape.
12.Which fitting changes pipe direction?
A. Coupling
B. Elbow
C. Tee
EXAM QUESTIONS AND CORRECT
ANSWERS (VERIFIED ANSWERS) PLUS
RATIONALES 2026 Q&A | INSTANT
DOWNLOAD PDF
1. What is the standard slope for a 4-inch sewer line?
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 is the minimum recommended slope to
maintain self-cleaning velocity and prevent solids deposition.
2. What does “DWV” stand for in plumbing?
A. Drain, Waste, and Vent
B. Domestic Water Valve
C. Direct Water Velocity
D. Drainage Water Volume
Rationale: DWV refers to the system that removes sewage and venting
gases to prevent traps from being siphoned.
3. What material is commonly used for residential cold water supply lines?
A. Cast iron
B. Lead
C. Copper
D. Galvanized steel
, Rationale: Copper tubing (Type L or M) is widely accepted due to
durability and corrosion resistance.
4. Which type of pipe is prohibited for potable water in most jurisdictions?
A. PVC
B. PEX
C. Polybutylene
D. CPVC
Rationale: Polybutylene was banned due to widespread failures and leaks.
5. What device prevents backflow in a plumbing system?
A. Drain cock
B. Pressure reducer
C. Backflow preventer
D. Ball valve
Rationale: Backflow preventers protect potable water from contamination
due to reverse flow.
6. What is the minimum trap arm length before it can turn vertically?
A. 6 inches
B. 2 times pipe diameter
C. 3 feet
D. 12 inches
Rationale: Trap arm must be at least twice the pipe diameter to avoid
siphonage.
7. What is the typical PSI rating for residential water pressure?
A. 30–40 PSI
B. 40–80 PSI
C. 80–100 PSI
D. 100–120 PSI
Rationale: Most residential systems operate between 40–80 PSI for safety
and performance.
, 8. Where must a cleanout be installed on a horizontal drain?
A. At every 20 feet
B. Only at the building entrance
C. At changes of direction >45°
D. Only at the footer
Rationale: Cleanouts allow access for maintenance where blockage is
likely.
9. What is used to join two lengths of copper pipe?
A. Thread compound
B. Compression fitting
C. Soldered fitting
D. PVC cement
Rationale: Copper is commonly joined by soldering with flux to create a
watertight seal.
10.Which gas is dangerous if allowed to accumulate in the plumbing system?
A. Oxygen
B. Nitrogen
C. Hydrogen sulfide
D. Carbon monoxide
Rationale: Hydrogen sulfide in sewer gas is toxic and corrosive.
11.What is the purpose of a vent in plumbing?
A. Increase water pressure
B. Filter impurities
C. Equalize pressure and remove gases
D. Heat waste water
Rationale: Vents prevent traps from siphoning and allow sewer gas to
escape.
12.Which fitting changes pipe direction?
A. Coupling
B. Elbow
C. Tee
