New Jersey Master Plumber Licensing
Examination Questions And Correct
Answers (Verified Answers) Plus
Rationale 2026 Q&A| Instant Download
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1. What is the minimum slope for a 3-inch horizontal drain per foot of
run?
A. 1/8"
B. 1/4"
C. 1/2"
D. 3/4"
Correct slope ensures proper drainage and prevents blockages.
2. The code requires a trap on every fixture. What is the primary purpose
of a trap?
A. Increase flow
B. Reduce pipe noise
C. Prevent sewer gases from entering the building
D. Provide access for cleaning
Traps create a water seal to block sewer gases.
3. What is the maximum distance a water closet can be from a vent?
A. 3 feet
B. 5 feet
C. 10 feet
D. 12 feet
Distance limits ensure effective venting.
4. A vent stack must extend at least how many inches above the roof?
A. 4"
, B. 6"
C. 12"
D. 24"
Minimum height prevents downdrafts and clogging from debris.
5. The protective atmosphere required around a gas vent termination is:
A. 2 feet from openings
B. 3 feet from openings
C. 6 inches
D. 1 foot
Clearance prevents combustion products entering the building.
6. Which of the following is used to join copper tubing to fittings?
A. PVC cement
B. Solder
C. Thread seal tape
D. Compression only
Soldering creates a leak-proof joint.
7. What is the minimum size for a residential water service?
A. 3/4"
B. 1"
C. 1-1/4"
D. 1-1/2"
1" service meets most NJ residential requirements.
8. Which device prevents backflow by allowing air into the system?
A. Check valve
B. Foot valve
C. Air gap
D. Pressure vacuum breaker
Air gaps provide physical separation to prevent backflow.
9. What is the minimum number of plumbing fixtures required in a
dwelling unit?
A. 1
B. 2
C. 3
D. 4
NJ Code generally requires a lavatory, water closet, and tub/shower.
, 10. What is the required clearance in front of a water closet?
A. 18"
B. 21"
C. 24"
D. 30"
Clearance ensures user comfort and access.
11. Which of the following materials is prohibited for underground
potable water service?
A. Copper
B. Galvanized steel
C. PEX
D. Ductile iron
Galvanized steel corrodes over time underground.
12. What type of valve must be installed on the building’s main
water supply?
A. Check valve
B. Shut-off valve
C. Vacuum breaker
D. Pressure regulator
Allows complete shut-off of water for maintenance or emergencies.
13. What is the minimum size trap arm for a lavatory?
A. 1-1/2"
B. 2"
C. 3"
D. 4"
Lavatories often require 2" to prevent siphoning.
14. What’s the maximum developed length of a horizontal drain
from a fixture to a vent for a 2-inch pipe?
A. 4 feet
B. 5 feet
C. 6 feet
D. 8 feet
This limit maintains trap seal integrity.
15. A water heater relief valve must be set to open at:
A. 100 psi
Examination Questions And Correct
Answers (Verified Answers) Plus
Rationale 2026 Q&A| Instant Download
1. What is the minimum slope for a 3-inch horizontal drain per foot of
run?
A. 1/8"
B. 1/4"
C. 1/2"
D. 3/4"
Correct slope ensures proper drainage and prevents blockages.
2. The code requires a trap on every fixture. What is the primary purpose
of a trap?
A. Increase flow
B. Reduce pipe noise
C. Prevent sewer gases from entering the building
D. Provide access for cleaning
Traps create a water seal to block sewer gases.
3. What is the maximum distance a water closet can be from a vent?
A. 3 feet
B. 5 feet
C. 10 feet
D. 12 feet
Distance limits ensure effective venting.
4. A vent stack must extend at least how many inches above the roof?
A. 4"
, B. 6"
C. 12"
D. 24"
Minimum height prevents downdrafts and clogging from debris.
5. The protective atmosphere required around a gas vent termination is:
A. 2 feet from openings
B. 3 feet from openings
C. 6 inches
D. 1 foot
Clearance prevents combustion products entering the building.
6. Which of the following is used to join copper tubing to fittings?
A. PVC cement
B. Solder
C. Thread seal tape
D. Compression only
Soldering creates a leak-proof joint.
7. What is the minimum size for a residential water service?
A. 3/4"
B. 1"
C. 1-1/4"
D. 1-1/2"
1" service meets most NJ residential requirements.
8. Which device prevents backflow by allowing air into the system?
A. Check valve
B. Foot valve
C. Air gap
D. Pressure vacuum breaker
Air gaps provide physical separation to prevent backflow.
9. What is the minimum number of plumbing fixtures required in a
dwelling unit?
A. 1
B. 2
C. 3
D. 4
NJ Code generally requires a lavatory, water closet, and tub/shower.
, 10. What is the required clearance in front of a water closet?
A. 18"
B. 21"
C. 24"
D. 30"
Clearance ensures user comfort and access.
11. Which of the following materials is prohibited for underground
potable water service?
A. Copper
B. Galvanized steel
C. PEX
D. Ductile iron
Galvanized steel corrodes over time underground.
12. What type of valve must be installed on the building’s main
water supply?
A. Check valve
B. Shut-off valve
C. Vacuum breaker
D. Pressure regulator
Allows complete shut-off of water for maintenance or emergencies.
13. What is the minimum size trap arm for a lavatory?
A. 1-1/2"
B. 2"
C. 3"
D. 4"
Lavatories often require 2" to prevent siphoning.
14. What’s the maximum developed length of a horizontal drain
from a fixture to a vent for a 2-inch pipe?
A. 4 feet
B. 5 feet
C. 6 feet
D. 8 feet
This limit maintains trap seal integrity.
15. A water heater relief valve must be set to open at:
A. 100 psi
