Journeyman Plumber Licensing Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the minimum size of a trap arm for a water closet?
A) 2 inches
B) 3 inches
C) 4 inches
D) 1½ inches
Rationale: Water closets require a minimum 3-inch trap arm to properly
handle waste discharge and prevent clogging.
2. The main purpose of a plumbing vent is to:
A) Provide water to fixtures
B) Equalize air pressure in the drainage system
C) Stop sewer gas leaks
D) Increase water flow
,Rationale: Vents prevent negative pressure that could siphon traps and
allow smooth waste flow.
3. What type of fitting is used to connect two pipes of different sizes in a
straight line?
A) Elbow
B) Reducer coupling
C) Cross
D) Wye
Rationale: A reducer coupling transitions between different pipe diameters
while maintaining alignment.
4. The minimum slope for a 3-inch horizontal drainage pipe is:
A) ¼ inch per foot
B) ⅛ inch per foot
C) ½ inch per foot
D) 1 inch per foot
Rationale: ⅛ inch per foot is sufficient for 3-inch or larger pipes to maintain
flow without excessive velocity.
5. A plumbing trap must:
A) Be vented on the outlet side only
,B) Hold at least 4 inches of water
C) Seal against sewer gases
D) Be installed vertically
Rationale: The trap’s water seal blocks sewer gases from entering living
spaces.
6. What type of valve is commonly used on gas lines?
A) Gate valve
B) Globe valve
C) Ball valve
D) Check valve
Rationale: Ball valves allow quick shutoff and are suitable for gas line
safety.
7. A water heater’s temperature relief valve must discharge:
A) Into a vent stack
B) Into a floor drain
C) Onto the floor
D) To an approved discharge location by gravity
Rationale: T&P valves must safely discharge by gravity to prevent scalding
or pressure buildup.
, 8. Which of the following materials is approved for underground drainage
piping?
A) Galvanized steel
B) PVC (Schedule 40)
C) Copper DWV
D) Lead
Rationale: PVC Schedule 40 is corrosion-resistant and widely approved for
underground use.
9. The maximum trap seal depth allowed by code is typically:
A) ½ inch
B) 1 inch
C) 4 inches
D) 6 inches
Rationale: Excessive trap seal depth can slow drainage and lead to
siphonage.
10. What is the minimum distance between a cleanout and the wall it faces?
A) 6 inches
B) 12 inches
C) 18 inches
D) 24 inches
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the minimum size of a trap arm for a water closet?
A) 2 inches
B) 3 inches
C) 4 inches
D) 1½ inches
Rationale: Water closets require a minimum 3-inch trap arm to properly
handle waste discharge and prevent clogging.
2. The main purpose of a plumbing vent is to:
A) Provide water to fixtures
B) Equalize air pressure in the drainage system
C) Stop sewer gas leaks
D) Increase water flow
,Rationale: Vents prevent negative pressure that could siphon traps and
allow smooth waste flow.
3. What type of fitting is used to connect two pipes of different sizes in a
straight line?
A) Elbow
B) Reducer coupling
C) Cross
D) Wye
Rationale: A reducer coupling transitions between different pipe diameters
while maintaining alignment.
4. The minimum slope for a 3-inch horizontal drainage pipe is:
A) ¼ inch per foot
B) ⅛ inch per foot
C) ½ inch per foot
D) 1 inch per foot
Rationale: ⅛ inch per foot is sufficient for 3-inch or larger pipes to maintain
flow without excessive velocity.
5. A plumbing trap must:
A) Be vented on the outlet side only
,B) Hold at least 4 inches of water
C) Seal against sewer gases
D) Be installed vertically
Rationale: The trap’s water seal blocks sewer gases from entering living
spaces.
6. What type of valve is commonly used on gas lines?
A) Gate valve
B) Globe valve
C) Ball valve
D) Check valve
Rationale: Ball valves allow quick shutoff and are suitable for gas line
safety.
7. A water heater’s temperature relief valve must discharge:
A) Into a vent stack
B) Into a floor drain
C) Onto the floor
D) To an approved discharge location by gravity
Rationale: T&P valves must safely discharge by gravity to prevent scalding
or pressure buildup.
, 8. Which of the following materials is approved for underground drainage
piping?
A) Galvanized steel
B) PVC (Schedule 40)
C) Copper DWV
D) Lead
Rationale: PVC Schedule 40 is corrosion-resistant and widely approved for
underground use.
9. The maximum trap seal depth allowed by code is typically:
A) ½ inch
B) 1 inch
C) 4 inches
D) 6 inches
Rationale: Excessive trap seal depth can slow drainage and lead to
siphonage.
10. What is the minimum distance between a cleanout and the wall it faces?
A) 6 inches
B) 12 inches
C) 18 inches
D) 24 inches
