Journeyman Plumber Licensing Exam

Journeyman Plumber Licensing Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the minimum slope required for a 3-inch horizontal drain line?
• 1/8 inch per foot
• 1/4 inch per foot
• 3/8 inch per foot
• 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.

• 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?

• 30 feet
• 50 feet 1 / 4

• 75 feet
• 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:

• Prevent freezing of the system
• Provide water for traps
• Equalize air pressure and prevent trap siphonage
• Drain rainwater

Rationale: Vents equalize air pressure in the drainage system, maintaining

trap seals and preventing siphonage.

• Which type of pipe is most commonly used for natural gas distribution?

A. PVC

B. CPVC

• Black steel
• Copper

Rationale: Black steel pipe is the standard material for natural gas piping

due to strength and compatibility.

• / 4

• The minimum air gap for a fixture outlet above the flood-level rim of a

receptor shall be:

• One pipe diameter
• Two pipe diameters
• Three pipe diameters
• Four pipe diameters

Rationale: Codes specify a minimum air gap of two pipe diameters to

prevent backflow contamination.

• What is the minimum trap diameter required for a kitchen sink?
• 1 inch
• 1 1/4 inches
• 1 1/2 inches
• 2 inches

Rationale: Kitchen sinks require 1 1/2-inch traps to handle grease and

solids without clogging.

• What is the primary function of a cleanout fitting?
• To test system pressure
• To allow access for drain cleaning
• To provide venting
• To trap debris 3 / 4

Rationale: Cleanouts allow access for mechanical cleaning of drainage

pipes.

• The minimum distance between a water closet and a side wall (center to

wall) is:

• 10 inches
• 15 inches
• 18 inches
• 24 inches

Rationale: The plumbing code requires at least 15 inches from the

centerline of a water closet to the nearest obstruction.

• What is the standard water pressure range for most residential systems?
• 10–30 psi
• 40–80 psi
• 90–120 psi
• 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:

• 1/2 inch and 1 inch
• / 4