New Jersey Master Plumber Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A Instant Download Pdf
1. What is the minimum diameter of a building sewer that connects to a
private septic tank?
A. 2 inches
B. 3 inches
C. 4 inches
D. 6 inches
Rationale: New Jersey plumbing code requires a minimum 4-inch diameter
building sewer to ensure adequate flow and prevent clogging.
2. What is the maximum water supply pressure allowed for residential
plumbing fixtures?
A. 40 psi
B. 80 psi
C. 100 psi
D. 120 psi
Rationale: To prevent damage to fixtures and appliances, residential
plumbing systems are generally limited to 80 psi.
3. Which type of pipe is most commonly used for water service lines in New
Jersey?
A. PVC
, B. ABS
C. Copper
D. Galvanized steel
Rationale: Copper tubing is widely used for water service lines due to its
durability and code compliance in New Jersey.
4. What is the minimum slope for a 4-inch diameter horizontal building drain?
A. 1/16 inch per foot
B. 1/8 inch per foot
C. 1/4 inch per foot
D. 1/2 inch per foot
Rationale: Proper drainage requires a 1/4 inch per foot slope for a 4-inch
horizontal building drain to prevent sediment accumulation.
5. Which valve is required to be installed on the water supply to a residential
water heater?
A. Ball valve only
B. Temperature and pressure relief valve
C. Gate valve
D. Check valve
Rationale: A T&P relief valve protects against excessive temperature or
pressure, which could cause water heater failure or explosion.
6. For a water closet, what is the minimum trap size?
A. 1-1/4 inches
B. 3 inches
C. 4 inches
D. 6 inches
Rationale: The code specifies a minimum 3-inch trap for water closets to
ensure proper trap seal and prevent siphoning.
7. How often must a backflow prevention assembly on a fire sprinkler system
be tested in New Jersey?
A. Monthly
B. Annually
, C. Every 12 months
D. Every 5 years
Rationale: New Jersey regulations require annual testing of backflow
preventers to maintain safe drinking water protection.
8. What is the minimum distance a water service line must be buried below
frost line in New Jersey?
A. 12 inches
B. 24 inches
C. 36 inches
D. 48 inches
Rationale: Burying water lines below the frost line prevents freezing; in
NJ, 36 inches is typical for most areas.
9. Which fixture is required to have an air gap between the supply and the
fixture?
A. Toilet
B. Lavatory
C. Kitchen sink
D. Bathtub
Rationale: Air gaps are required on fixtures like kitchen sinks to prevent
cross-connection contamination from sinks to potable water supply.
10.What is the maximum horizontal spacing between supports for 1-inch Type
L copper water tubing?
A. 3 feet
B. 4 feet
C. 6 feet
D. 8 feet
Rationale: Code specifies supports every 6 feet for 1-inch Type L copper to
prevent sagging and stress.
11.What is the minimum trap seal depth for a standard P-trap?
A. 1 inch
B. 2 inches
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A Instant Download Pdf
1. What is the minimum diameter of a building sewer that connects to a
private septic tank?
A. 2 inches
B. 3 inches
C. 4 inches
D. 6 inches
Rationale: New Jersey plumbing code requires a minimum 4-inch diameter
building sewer to ensure adequate flow and prevent clogging.
2. What is the maximum water supply pressure allowed for residential
plumbing fixtures?
A. 40 psi
B. 80 psi
C. 100 psi
D. 120 psi
Rationale: To prevent damage to fixtures and appliances, residential
plumbing systems are generally limited to 80 psi.
3. Which type of pipe is most commonly used for water service lines in New
Jersey?
A. PVC
, B. ABS
C. Copper
D. Galvanized steel
Rationale: Copper tubing is widely used for water service lines due to its
durability and code compliance in New Jersey.
4. What is the minimum slope for a 4-inch diameter horizontal building drain?
A. 1/16 inch per foot
B. 1/8 inch per foot
C. 1/4 inch per foot
D. 1/2 inch per foot
Rationale: Proper drainage requires a 1/4 inch per foot slope for a 4-inch
horizontal building drain to prevent sediment accumulation.
5. Which valve is required to be installed on the water supply to a residential
water heater?
A. Ball valve only
B. Temperature and pressure relief valve
C. Gate valve
D. Check valve
Rationale: A T&P relief valve protects against excessive temperature or
pressure, which could cause water heater failure or explosion.
6. For a water closet, what is the minimum trap size?
A. 1-1/4 inches
B. 3 inches
C. 4 inches
D. 6 inches
Rationale: The code specifies a minimum 3-inch trap for water closets to
ensure proper trap seal and prevent siphoning.
7. How often must a backflow prevention assembly on a fire sprinkler system
be tested in New Jersey?
A. Monthly
B. Annually
, C. Every 12 months
D. Every 5 years
Rationale: New Jersey regulations require annual testing of backflow
preventers to maintain safe drinking water protection.
8. What is the minimum distance a water service line must be buried below
frost line in New Jersey?
A. 12 inches
B. 24 inches
C. 36 inches
D. 48 inches
Rationale: Burying water lines below the frost line prevents freezing; in
NJ, 36 inches is typical for most areas.
9. Which fixture is required to have an air gap between the supply and the
fixture?
A. Toilet
B. Lavatory
C. Kitchen sink
D. Bathtub
Rationale: Air gaps are required on fixtures like kitchen sinks to prevent
cross-connection contamination from sinks to potable water supply.
10.What is the maximum horizontal spacing between supports for 1-inch Type
L copper water tubing?
A. 3 feet
B. 4 feet
C. 6 feet
D. 8 feet
Rationale: Code specifies supports every 6 feet for 1-inch Type L copper to
prevent sagging and stress.
11.What is the minimum trap seal depth for a standard P-trap?
A. 1 inch
B. 2 inches
