NYC Master Plumber License Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. Which of the following materials is approved for potable water supply
in NYC?
A) Lead
B) Copper
C) Galvanized iron
D) Asbestos-cement
Rationale: Copper is widely approved for potable water because it is
durable, corrosion-resistant, and safe for drinking water.
2. The minimum slope for a 2-inch horizontal DWV (drain, waste, vent)
pipe is:
A) 1/8 inch per foot
B) 1/4 inch per foot
, C) 1/4 to 1/2 inch per foot
D) 1/2 inch per foot
Rationale: NYC Plumbing Code requires horizontal DWV pipes to
slope between 1/4 to 1/2 inch per foot to ensure proper drainage.
3. What is the maximum allowable water temperature for a residential
hot water heater?
A) 140°F
B) 160°F
C) 120°F
D) 180°F
Rationale: To prevent scalding, the NYC Plumbing Code limits
residential hot water to 120°F at outlets.
4. Which of the following is required to prevent backflow in a water
supply system?
A) Check valve
B) Backflow preventer
C) Pressure-reducing valve
D) Air gap only
Rationale: A backflow preventer is specifically designed to prevent
contamination of the potable water supply.
5. The vent terminal of a building plumbing system must extend at least
how many inches above the roof?
A) 6 inches
, B) 12 inches
C) 24 inches
D) 18 inches
Rationale: NYC Plumbing Code requires vent terminals to extend at
least 12 inches above the roof to prevent sewer gas from entering
the building.
6. What type of pipe joint is commonly used for cast iron soil pipe
connections?
A) Threaded
B) Solvent weld
C) Hub and spigot with no-hub coupling
D) Compression
Rationale: Cast iron soil pipes are joined using hub and spigot fittings
with approved couplings to provide leak-free connections.
7. What is the minimum trap seal depth for a fixture in NYC?
A) 1 inch
B) 2 inches
C) 2 inches minimum, 4 inches maximum
D) 6 inches
Rationale: A trap seal depth of 2–4 inches is required to maintain a
water barrier while preventing siphoning.
8. What is the correct method to test a new water supply installation for
leaks?
, A) Visual inspection only
B) Hydrostatic pressure test
C) Air or hydrostatic pressure test
D) Flow test only
Rationale: Plumbing installations are tested using air or water
pressure to ensure there are no leaks.
9. Which NYC code governs the installation of plumbing systems?
A) International Plumbing Code
B) National Standard Plumbing Code
C) NYC Plumbing Code
D) Uniform Plumbing Code
Rationale: The NYC Plumbing Code sets all legal requirements for
plumbing design, installation, and maintenance in New York City.
10. What is the minimum size of a vent pipe for a single water
closet?
A) 1 inch
B) 1 1/4 inches
C) 2 inches
D) 3 inches
Rationale: A 2-inch vent is required for a water closet to ensure
adequate venting and prevent siphoning.
11. In NYC, what is the maximum number of fixture units allowed on
a 3-inch horizontal drain?
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. Which of the following materials is approved for potable water supply
in NYC?
A) Lead
B) Copper
C) Galvanized iron
D) Asbestos-cement
Rationale: Copper is widely approved for potable water because it is
durable, corrosion-resistant, and safe for drinking water.
2. The minimum slope for a 2-inch horizontal DWV (drain, waste, vent)
pipe is:
A) 1/8 inch per foot
B) 1/4 inch per foot
, C) 1/4 to 1/2 inch per foot
D) 1/2 inch per foot
Rationale: NYC Plumbing Code requires horizontal DWV pipes to
slope between 1/4 to 1/2 inch per foot to ensure proper drainage.
3. What is the maximum allowable water temperature for a residential
hot water heater?
A) 140°F
B) 160°F
C) 120°F
D) 180°F
Rationale: To prevent scalding, the NYC Plumbing Code limits
residential hot water to 120°F at outlets.
4. Which of the following is required to prevent backflow in a water
supply system?
A) Check valve
B) Backflow preventer
C) Pressure-reducing valve
D) Air gap only
Rationale: A backflow preventer is specifically designed to prevent
contamination of the potable water supply.
5. The vent terminal of a building plumbing system must extend at least
how many inches above the roof?
A) 6 inches
, B) 12 inches
C) 24 inches
D) 18 inches
Rationale: NYC Plumbing Code requires vent terminals to extend at
least 12 inches above the roof to prevent sewer gas from entering
the building.
6. What type of pipe joint is commonly used for cast iron soil pipe
connections?
A) Threaded
B) Solvent weld
C) Hub and spigot with no-hub coupling
D) Compression
Rationale: Cast iron soil pipes are joined using hub and spigot fittings
with approved couplings to provide leak-free connections.
7. What is the minimum trap seal depth for a fixture in NYC?
A) 1 inch
B) 2 inches
C) 2 inches minimum, 4 inches maximum
D) 6 inches
Rationale: A trap seal depth of 2–4 inches is required to maintain a
water barrier while preventing siphoning.
8. What is the correct method to test a new water supply installation for
leaks?
, A) Visual inspection only
B) Hydrostatic pressure test
C) Air or hydrostatic pressure test
D) Flow test only
Rationale: Plumbing installations are tested using air or water
pressure to ensure there are no leaks.
9. Which NYC code governs the installation of plumbing systems?
A) International Plumbing Code
B) National Standard Plumbing Code
C) NYC Plumbing Code
D) Uniform Plumbing Code
Rationale: The NYC Plumbing Code sets all legal requirements for
plumbing design, installation, and maintenance in New York City.
10. What is the minimum size of a vent pipe for a single water
closet?
A) 1 inch
B) 1 1/4 inches
C) 2 inches
D) 3 inches
Rationale: A 2-inch vent is required for a water closet to ensure
adequate venting and prevent siphoning.
11. In NYC, what is the maximum number of fixture units allowed on
a 3-inch horizontal drain?
