Minnesota Restricted Journeyman
Plumber Exam Practice Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
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1. What is the primary purpose of a plumbing trap?
A) To increase water pressure
B) To prevent sewer gases from entering the building
C) To increase drainage speed
D) To filter solid waste
Answer: B
A plumbing trap maintains a water seal that blocks sewer gases and
odors from entering occupied spaces while still allowing wastewater
to pass through.
2. Which of the following is the minimum slope for a 2-inch horizontal
drain line under most plumbing codes?
A) 1/8 inch per foot
, B) 1/4 inch per foot
C) 1/2 inch per foot
D) 1 inch per foot
Answer: B
A 1/4 inch per foot slope ensures adequate flow velocity to carry
solids without causing excessive drainage speed or pipe noise issues.
3. What material is commonly used for DWV systems in modern
residential plumbing?
A) Copper Type L
B) Galvanized steel
C) PVC
D) Brass
Answer: C
PVC is widely used in drain-waste-vent systems due to its corrosion
resistance, affordability, and ease of installation.
4. What is the purpose of a vent system in plumbing?
A) To carry waste to the sewer
B) To supply oxygen to water heaters
C) To allow air into the drainage system for proper flow
D) To increase water pressure
Answer: C
A vent system equalizes air pressure in drain pipes, preventing
siphoning of traps and ensuring smooth wastewater flow.
,5. Which fitting is used to change direction in a drain line with minimal
resistance?
A) Sanitary tee
B) Closet flange
C) Long-sweep elbow
D) Cap
Answer: C
Long-sweep elbows are designed to reduce turbulence and maintain
flow efficiency in drainage systems.
6. What is the function of a cleanout in a drainage system?
A) To increase water flow
B) To allow access for removing blockages
C) To regulate pressure
D) To filter solids
Answer: B
Cleanouts provide access points for maintenance and clearing
obstructions in drain lines.
7. Which pipe is commonly used for hot and cold water distribution in
residential systems?
A) ABS
B) PEX
C) Clay pipe
D) Cast iron
, Answer: B
PEX tubing is flexible, resistant to scale and chlorine, and widely used
for potable water distribution.
8. What is the minimum required air gap for a dishwasher drain line?
A) 1 inch
B) 2 inches
C) 4 inches
D) 6 inches
Answer: B
A 2-inch air gap prevents backflow contamination between the
dishwasher and potable water supply.
9. Which device prevents backflow in a plumbing system?
A) Pressure gauge
B) Backflow preventer
C) Expansion tank
D) Air chamber
Answer: B
Backflow preventers ensure contaminated water cannot reverse flow
into clean water supplies.
10. What is the main function of a P-trap?
A) Increase pressure
B) Store debris
C) Maintain water seal against sewer gases
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 prevent sewer gases from entering the building
C) To increase drainage speed
D) To filter solid waste
Answer: B
A plumbing trap maintains a water seal that blocks sewer gases and
odors from entering occupied spaces while still allowing wastewater
to pass through.
2. Which of the following is the minimum slope for a 2-inch horizontal
drain line under most plumbing codes?
A) 1/8 inch per foot
, B) 1/4 inch per foot
C) 1/2 inch per foot
D) 1 inch per foot
Answer: B
A 1/4 inch per foot slope ensures adequate flow velocity to carry
solids without causing excessive drainage speed or pipe noise issues.
3. What material is commonly used for DWV systems in modern
residential plumbing?
A) Copper Type L
B) Galvanized steel
C) PVC
D) Brass
Answer: C
PVC is widely used in drain-waste-vent systems due to its corrosion
resistance, affordability, and ease of installation.
4. What is the purpose of a vent system in plumbing?
A) To carry waste to the sewer
B) To supply oxygen to water heaters
C) To allow air into the drainage system for proper flow
D) To increase water pressure
Answer: C
A vent system equalizes air pressure in drain pipes, preventing
siphoning of traps and ensuring smooth wastewater flow.
,5. Which fitting is used to change direction in a drain line with minimal
resistance?
A) Sanitary tee
B) Closet flange
C) Long-sweep elbow
D) Cap
Answer: C
Long-sweep elbows are designed to reduce turbulence and maintain
flow efficiency in drainage systems.
6. What is the function of a cleanout in a drainage system?
A) To increase water flow
B) To allow access for removing blockages
C) To regulate pressure
D) To filter solids
Answer: B
Cleanouts provide access points for maintenance and clearing
obstructions in drain lines.
7. Which pipe is commonly used for hot and cold water distribution in
residential systems?
A) ABS
B) PEX
C) Clay pipe
D) Cast iron
, Answer: B
PEX tubing is flexible, resistant to scale and chlorine, and widely used
for potable water distribution.
8. What is the minimum required air gap for a dishwasher drain line?
A) 1 inch
B) 2 inches
C) 4 inches
D) 6 inches
Answer: B
A 2-inch air gap prevents backflow contamination between the
dishwasher and potable water supply.
9. Which device prevents backflow in a plumbing system?
A) Pressure gauge
B) Backflow preventer
C) Expansion tank
D) Air chamber
Answer: B
Backflow preventers ensure contaminated water cannot reverse flow
into clean water supplies.
10. What is the main function of a P-trap?
A) Increase pressure
B) Store debris
C) Maintain water seal against sewer gases
