Journeyman Plumber Licensing Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the minimum slope required for a 3-inch horizontal drain line?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 3/8 inch per foot
D. 1/2 inch per foot
Rationale: Plumbing codes require a minimum slope of 1/4 inch per foot
for 2 1/2-inch through 3-inch pipes to ensure proper drainage velocity.
2. The maximum developed length of a 1/2-inch water supply line to a
fixture should not exceed how many feet before upsizing is required?
A. 30 feet
B. 50 feet
,C. 75 feet
D. 100 feet
Rationale: Pressure loss limits for 1/2-inch lines are typically around 50
feet; beyond this, upsizing prevents insufficient flow.
3. The purpose of a vent system in a plumbing installation is to:
A. Prevent freezing of the system
B. Provide water for traps
C. Equalize air pressure and prevent trap siphonage
D. Drain rainwater
Rationale: Vents equalize air pressure in the drainage system, maintaining
trap seals and preventing siphonage.
4. Which type of pipe is most commonly used for natural gas distribution?
A. PVC
B. CPVC
C. Black steel
D. Copper
Rationale: Black steel pipe is the standard material for natural gas piping
due to strength and compatibility.
,5. The minimum air gap for a fixture outlet above the flood-level rim of a
receptor shall be:
A. One pipe diameter
B. Two pipe diameters
C. Three pipe diameters
D. Four pipe diameters
Rationale: Codes specify a minimum air gap of two pipe diameters to
prevent backflow contamination.
6. What is the minimum trap diameter required for a kitchen sink?
A. 1 inch
B. 1 1/4 inches
C.1 1/2 inches
D. 2 inches
Rationale: Kitchen sinks require 1 1/2-inch traps to handle grease and
solids without clogging.
7. What is the primary function of a cleanout fitting?
A. To test system pressure
B. To allow access for drain cleaning
C. To provide venting
D. To trap debris
, Rationale: Cleanouts allow access for mechanical cleaning of drainage
pipes.
8. The minimum distance between a water closet and a side wall (center to
wall) is:
A. 10 inches
B. 15 inches
C. 18 inches
D. 24 inches
Rationale: The plumbing code requires at least 15 inches from the
centerline of a water closet to the nearest obstruction.
9. What is the standard water pressure range for most residential systems?
A. 10–30 psi
B. 40–80 psi
C. 90–120 psi
D. 130–150 psi
Rationale: The typical safe and functional residential water pressure range
is 40–80 psi.
10. A trap seal depth should be between:
A. 1/2 inch and 1 inch
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the minimum slope required for a 3-inch horizontal drain line?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 3/8 inch per foot
D. 1/2 inch per foot
Rationale: Plumbing codes require a minimum slope of 1/4 inch per foot
for 2 1/2-inch through 3-inch pipes to ensure proper drainage velocity.
2. The maximum developed length of a 1/2-inch water supply line to a
fixture should not exceed how many feet before upsizing is required?
A. 30 feet
B. 50 feet
,C. 75 feet
D. 100 feet
Rationale: Pressure loss limits for 1/2-inch lines are typically around 50
feet; beyond this, upsizing prevents insufficient flow.
3. The purpose of a vent system in a plumbing installation is to:
A. Prevent freezing of the system
B. Provide water for traps
C. Equalize air pressure and prevent trap siphonage
D. Drain rainwater
Rationale: Vents equalize air pressure in the drainage system, maintaining
trap seals and preventing siphonage.
4. Which type of pipe is most commonly used for natural gas distribution?
A. PVC
B. CPVC
C. Black steel
D. Copper
Rationale: Black steel pipe is the standard material for natural gas piping
due to strength and compatibility.
,5. The minimum air gap for a fixture outlet above the flood-level rim of a
receptor shall be:
A. One pipe diameter
B. Two pipe diameters
C. Three pipe diameters
D. Four pipe diameters
Rationale: Codes specify a minimum air gap of two pipe diameters to
prevent backflow contamination.
6. What is the minimum trap diameter required for a kitchen sink?
A. 1 inch
B. 1 1/4 inches
C.1 1/2 inches
D. 2 inches
Rationale: Kitchen sinks require 1 1/2-inch traps to handle grease and
solids without clogging.
7. What is the primary function of a cleanout fitting?
A. To test system pressure
B. To allow access for drain cleaning
C. To provide venting
D. To trap debris
, Rationale: Cleanouts allow access for mechanical cleaning of drainage
pipes.
8. The minimum distance between a water closet and a side wall (center to
wall) is:
A. 10 inches
B. 15 inches
C. 18 inches
D. 24 inches
Rationale: The plumbing code requires at least 15 inches from the
centerline of a water closet to the nearest obstruction.
9. What is the standard water pressure range for most residential systems?
A. 10–30 psi
B. 40–80 psi
C. 90–120 psi
D. 130–150 psi
Rationale: The typical safe and functional residential water pressure range
is 40–80 psi.
10. A trap seal depth should be between:
A. 1/2 inch and 1 inch
