New York Master Plumber Licensing Exam
Practice Questions with Detailed Rationales
latest 2026 Latest version Q&A |INSTANT
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1. What is the minimum slope for a 3-inch horizontal drain pipe?
A. 1/8 in/ft
B. 3/16 in/ft
C. 1/4 in/ft
D. 1/2 in/ft
Correct drain slope prevents sewer solids settling.
2. How many fixture units is a toilet (water closet) assigned in NYC?
A. 2
B. 3
C. 4
D. 6
NYC/UPC assigns 4 DFU to a standard water closet.
3. Which material is generally prohibited for potable water service in
New York?
A. Copper
B. PEX
C. Lead
D. CPVC
Lead is banned due to toxicity.
4. What is the minimum distance a vent must be from a trap weir to
avoid siphonage?
,A. 2 pipe diameters
B. 6 pipe diameters
C. 10 pipe diameters
D. 20 pipe diameters
Proper vent placement protects trap seal.
5. What device protects potable water from backflow due to
backpressure?
A. Air gap
B. Check valve
C. Reduced Pressure Zone (RPZ) assembly
D. Gate valve
RPZ provides high-level backflow protection.
6. How deep must water service pipe be buried in NYC (typically)?
A. 6”
B. 12”
C. 36”
D. 60”
Frost line protection and code minimum.
7. What is the minimum size vent for a group of fixtures if the drain
serving them is 4”?
A. 1½”
B. 2”
C. 3”
D. 4”
Larger drains require larger vents.
8. What is the standard distance for an air gap at a hose bib?
, A. 1 inch
B. 2 times diameter
C. Equal to pipe size
D. 5 inches
Air gaps must be twice the supply line diameter.
9. What is the primary purpose of a trap?
A. Increase flow
B. Prevent sewer gas entry
C. Reduce pressure
D. Filter debris
Trap seals block sewer gases.
10. What fixture requires a 3-inch drain minimum?
A. Lavatory
B. Dishwasher
C. Urinal
D. Floor drain
Floor drains require larger capacity.
11. Which valve is best for throttling flow?
A. Gate
B. Globe
C. Ball
D. Butterfly
Globe valves allow controlled throttling.
12. What is the minimum size water heater relief valve discharge
pipe?
Practice Questions with Detailed Rationales
latest 2026 Latest version Q&A |INSTANT
DOWNLOAD PDF
1. What is the minimum slope for a 3-inch horizontal drain pipe?
A. 1/8 in/ft
B. 3/16 in/ft
C. 1/4 in/ft
D. 1/2 in/ft
Correct drain slope prevents sewer solids settling.
2. How many fixture units is a toilet (water closet) assigned in NYC?
A. 2
B. 3
C. 4
D. 6
NYC/UPC assigns 4 DFU to a standard water closet.
3. Which material is generally prohibited for potable water service in
New York?
A. Copper
B. PEX
C. Lead
D. CPVC
Lead is banned due to toxicity.
4. What is the minimum distance a vent must be from a trap weir to
avoid siphonage?
,A. 2 pipe diameters
B. 6 pipe diameters
C. 10 pipe diameters
D. 20 pipe diameters
Proper vent placement protects trap seal.
5. What device protects potable water from backflow due to
backpressure?
A. Air gap
B. Check valve
C. Reduced Pressure Zone (RPZ) assembly
D. Gate valve
RPZ provides high-level backflow protection.
6. How deep must water service pipe be buried in NYC (typically)?
A. 6”
B. 12”
C. 36”
D. 60”
Frost line protection and code minimum.
7. What is the minimum size vent for a group of fixtures if the drain
serving them is 4”?
A. 1½”
B. 2”
C. 3”
D. 4”
Larger drains require larger vents.
8. What is the standard distance for an air gap at a hose bib?
, A. 1 inch
B. 2 times diameter
C. Equal to pipe size
D. 5 inches
Air gaps must be twice the supply line diameter.
9. What is the primary purpose of a trap?
A. Increase flow
B. Prevent sewer gas entry
C. Reduce pressure
D. Filter debris
Trap seals block sewer gases.
10. What fixture requires a 3-inch drain minimum?
A. Lavatory
B. Dishwasher
C. Urinal
D. Floor drain
Floor drains require larger capacity.
11. Which valve is best for throttling flow?
A. Gate
B. Globe
C. Ball
D. Butterfly
Globe valves allow controlled throttling.
12. What is the minimum size water heater relief valve discharge
pipe?
