Journeyman Plumber Licensing Examination
Questions With Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A | Instant
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1.
What is the primary purpose of a P-trap in a plumbing system?
A. Increase water pressure
B. Prevent sewer gases from entering the building
C. Increase drainage speed
D. Filter solid waste
Answer: B
Rationale: A P-trap holds a small amount of water that creates a seal,
preventing sewer gases and odors from traveling back into the
occupied space.
2.
What is the minimum slope required for a 3-inch horizontal drain pipe
under most plumbing codes?
,A. 1/16 inch per foot
B. 1/8 inch per foot
C. 1/4 inch per foot
D. 1 inch per foot
Answer: B
Rationale: A 3-inch drain typically requires a minimum slope of 1/8
inch per foot to maintain proper flow velocity and prevent solids from
settling.
3.
Which pipe material is most commonly used for residential cold water
supply lines today?
A. Cast iron
B. Galvanized steel
C. PEX
D. Lead
Answer: C
Rationale: PEX is widely used due to its flexibility, corrosion resistance,
and ease of installation compared to older metallic piping systems.
,4.
What is the function of a vent pipe in a drainage system?
A. Carry wastewater to the sewer
B. Increase water pressure
C. Allow air into the system to maintain neutral pressure
D. Filter debris from wastewater
Answer: C
Rationale: Vent pipes prevent vacuum formation and allow air into the
system, ensuring smooth drainage and preventing trap siphonage.
5.
Which fitting is used to change direction 90 degrees in a drain line with
minimal flow resistance?
A. Sanitary tee
B. Elbow
C. Wye fitting
D. Coupling
Answer: C
Rationale: A wye fitting provides a smoother directional change,
, reducing turbulence and maintaining better flow compared to a sharp
elbow.
6.
What is backflow in plumbing?
A. Water flowing forward faster than normal
B. Reverse flow of contaminated water into clean water supply
C. Air entering drain lines
D. Increase in pipe pressure
Answer: B
Rationale: Backflow occurs when contaminated water flows backward
into potable water lines, posing a health hazard.
7.
Which device is used to prevent backflow in potable water systems?
A. Pressure gauge
B. Backflow preventer
C. Ball valve
D. Trap primer
Questions With Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A | Instant
Download Pdf
1.
What is the primary purpose of a P-trap in a plumbing system?
A. Increase water pressure
B. Prevent sewer gases from entering the building
C. Increase drainage speed
D. Filter solid waste
Answer: B
Rationale: A P-trap holds a small amount of water that creates a seal,
preventing sewer gases and odors from traveling back into the
occupied space.
2.
What is the minimum slope required for a 3-inch horizontal drain pipe
under most plumbing codes?
,A. 1/16 inch per foot
B. 1/8 inch per foot
C. 1/4 inch per foot
D. 1 inch per foot
Answer: B
Rationale: A 3-inch drain typically requires a minimum slope of 1/8
inch per foot to maintain proper flow velocity and prevent solids from
settling.
3.
Which pipe material is most commonly used for residential cold water
supply lines today?
A. Cast iron
B. Galvanized steel
C. PEX
D. Lead
Answer: C
Rationale: PEX is widely used due to its flexibility, corrosion resistance,
and ease of installation compared to older metallic piping systems.
,4.
What is the function of a vent pipe in a drainage system?
A. Carry wastewater to the sewer
B. Increase water pressure
C. Allow air into the system to maintain neutral pressure
D. Filter debris from wastewater
Answer: C
Rationale: Vent pipes prevent vacuum formation and allow air into the
system, ensuring smooth drainage and preventing trap siphonage.
5.
Which fitting is used to change direction 90 degrees in a drain line with
minimal flow resistance?
A. Sanitary tee
B. Elbow
C. Wye fitting
D. Coupling
Answer: C
Rationale: A wye fitting provides a smoother directional change,
, reducing turbulence and maintaining better flow compared to a sharp
elbow.
6.
What is backflow in plumbing?
A. Water flowing forward faster than normal
B. Reverse flow of contaminated water into clean water supply
C. Air entering drain lines
D. Increase in pipe pressure
Answer: B
Rationale: Backflow occurs when contaminated water flows backward
into potable water lines, posing a health hazard.
7.
Which device is used to prevent backflow in potable water systems?
A. Pressure gauge
B. Backflow preventer
C. Ball valve
D. Trap primer
