Minnesota Journeyman Plumber Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the primary purpose of a plumbing trap?
A. To increase water pressure
B. To filter solid waste
C. To prevent sewer gases from entering the building
D. To improve drainage speed
C. To prevent sewer gases from entering the building
Rationale: Plumbing traps maintain a water seal that blocks sewer gases
from traveling back into occupied spaces. This protects building occupants
from harmful gases and unpleasant odors.
2. Which type of pipe is commonly approved for residential water
distribution systems?
,A. Black steel pipe
B. ABS foam core pipe
C. PEX tubing
D. Clay tile pipe
C. PEX tubing
Rationale: PEX tubing is widely accepted for residential potable water
systems because it is flexible, corrosion resistant, and easy to install
compared to rigid piping materials.
3. What is the minimum slope generally required for a 3-inch horizontal
drainage pipe?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 1 inch per foot
B. 1/4 inch per foot
Rationale: Most plumbing codes require a minimum slope of 1/4 inch per
foot for horizontal drainage piping 3 inches or smaller to ensure proper
waste flow and prevent blockages.
4. Which plumbing fixture requires a vent?
,A. Every trapped fixture
B. Only toilets
C. Only sinks
D. Only floor drains
A. Every trapped fixture
Rationale: Every trapped fixture requires venting to maintain atmospheric
pressure in the drainage system and protect trap seals from siphonage or
backpressure.
5. What device protects a potable water supply from contamination
caused by backsiphonage?
A. Pressure regulator
B. Water hammer arrestor
C. Backflow preventer
D. Expansion tank
C. Backflow preventer
Rationale: A backflow preventer stops contaminated water from reversing
direction and entering the potable water supply due to backsiphonage or
backpressure conditions.
6. Which fixture unit load is typically the greatest in a residential
bathroom group?
, A. Lavatory
B. Bathtub
C. Water closet
D. Bidet
C. Water closet
Rationale: Water closets generally carry the highest fixture unit value
because they discharge the largest volume of waste and water into the
drainage system.
7. What is the purpose of a cleanout in a drainage system?
A. To vent sewer gases
B. To increase water pressure
C. To provide access for cleaning pipes
D. To reduce pipe corrosion
C. To provide access for cleaning pipes
Rationale: Cleanouts allow plumbers to inspect and remove obstructions
from drainage piping without dismantling the plumbing system.
8. Which material is prohibited for potable water distribution due to
health concerns?
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the primary purpose of a plumbing trap?
A. To increase water pressure
B. To filter solid waste
C. To prevent sewer gases from entering the building
D. To improve drainage speed
C. To prevent sewer gases from entering the building
Rationale: Plumbing traps maintain a water seal that blocks sewer gases
from traveling back into occupied spaces. This protects building occupants
from harmful gases and unpleasant odors.
2. Which type of pipe is commonly approved for residential water
distribution systems?
,A. Black steel pipe
B. ABS foam core pipe
C. PEX tubing
D. Clay tile pipe
C. PEX tubing
Rationale: PEX tubing is widely accepted for residential potable water
systems because it is flexible, corrosion resistant, and easy to install
compared to rigid piping materials.
3. What is the minimum slope generally required for a 3-inch horizontal
drainage pipe?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 1 inch per foot
B. 1/4 inch per foot
Rationale: Most plumbing codes require a minimum slope of 1/4 inch per
foot for horizontal drainage piping 3 inches or smaller to ensure proper
waste flow and prevent blockages.
4. Which plumbing fixture requires a vent?
,A. Every trapped fixture
B. Only toilets
C. Only sinks
D. Only floor drains
A. Every trapped fixture
Rationale: Every trapped fixture requires venting to maintain atmospheric
pressure in the drainage system and protect trap seals from siphonage or
backpressure.
5. What device protects a potable water supply from contamination
caused by backsiphonage?
A. Pressure regulator
B. Water hammer arrestor
C. Backflow preventer
D. Expansion tank
C. Backflow preventer
Rationale: A backflow preventer stops contaminated water from reversing
direction and entering the potable water supply due to backsiphonage or
backpressure conditions.
6. Which fixture unit load is typically the greatest in a residential
bathroom group?
, A. Lavatory
B. Bathtub
C. Water closet
D. Bidet
C. Water closet
Rationale: Water closets generally carry the highest fixture unit value
because they discharge the largest volume of waste and water into the
drainage system.
7. What is the purpose of a cleanout in a drainage system?
A. To vent sewer gases
B. To increase water pressure
C. To provide access for cleaning pipes
D. To reduce pipe corrosion
C. To provide access for cleaning pipes
Rationale: Cleanouts allow plumbers to inspect and remove obstructions
from drainage piping without dismantling the plumbing system.
8. Which material is prohibited for potable water distribution due to
health concerns?
