Nevada Plumbing Contractor
Exam Questions And Correct
Answers (Verified Answers)
Plus Rationales 2025/2026
Q&A | Instant Download Pdf
1. What is the minimum slope for a horizontal drainage pipe 3
inches or smaller?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 1 inch per foot
Rationale: Most plumbing codes require a minimum slope of 1/4" per
foot for 3" and smaller drain lines to ensure proper flow and prevent
solids buildup.
2. What is the purpose of a plumbing vent system?
A. Increase water pressure
B. Prevent freezing
C. Allow air into the drainage system and prevent trap siphonage
D. Filter wastewater
Rationale: Vent systems equalize air pressure in drainage piping,
protecting trap seals from being siphoned.
,3. What is the minimum size for a building sewer under most
codes?
A. 2 inches
B. 3 inches
C. 4 inches
D. 6 inches
Rationale: A 4-inch minimum is standard for building sewers to
handle solids and prevent clogging.
4. Which fixture requires a separate trap?
A. Two adjacent sinks
B. A dishwasher and sink combination
C. Each plumbing fixture must have its own trap
D. Floor drains only
Rationale: Plumbing codes generally prohibit shared traps between
fixtures.
5. What is the maximum distance a 1½-inch trap arm may travel
before venting?
A. 3 feet
B. 4 feet
C. 6 feet
D. 10 feet
Rationale: Trap arm length is limited to maintain trap seal integrity.
6. Which material is commonly used for underground drainage
piping?
A. Copper Type L
B. Galvanized steel
, C. PVC SDR 35 or ABS
D. Brass
Rationale: PVC and ABS are corrosion-resistant and approved for
underground drainage.
7. What is the minimum air gap required for potable water
protection?
A. 1/2 inch
B. Pipe diameter
C. Twice the diameter of the outlet or 1 inch minimum
D. 6 inches
Rationale: Air gaps prevent backflow contamination.
8. What device prevents backflow in a water system?
A. Trap
B. Cleanout
C. Backflow preventer
D. Vent stack
Rationale: Backflow preventers stop reverse flow of contaminated
water.
9. What is the purpose of a cleanout?
A. Increase flow
B. Vent sewer gas
C. Provide access for clearing blockages
D. Measure water pressure
Rationale: Cleanouts allow maintenance access to drainage systems.
10. What is the minimum slope for a 4-inch drain pipe?
Exam Questions And Correct
Answers (Verified Answers)
Plus Rationales 2025/2026
Q&A | Instant Download Pdf
1. What is the minimum slope for a horizontal drainage pipe 3
inches or smaller?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 1 inch per foot
Rationale: Most plumbing codes require a minimum slope of 1/4" per
foot for 3" and smaller drain lines to ensure proper flow and prevent
solids buildup.
2. What is the purpose of a plumbing vent system?
A. Increase water pressure
B. Prevent freezing
C. Allow air into the drainage system and prevent trap siphonage
D. Filter wastewater
Rationale: Vent systems equalize air pressure in drainage piping,
protecting trap seals from being siphoned.
,3. What is the minimum size for a building sewer under most
codes?
A. 2 inches
B. 3 inches
C. 4 inches
D. 6 inches
Rationale: A 4-inch minimum is standard for building sewers to
handle solids and prevent clogging.
4. Which fixture requires a separate trap?
A. Two adjacent sinks
B. A dishwasher and sink combination
C. Each plumbing fixture must have its own trap
D. Floor drains only
Rationale: Plumbing codes generally prohibit shared traps between
fixtures.
5. What is the maximum distance a 1½-inch trap arm may travel
before venting?
A. 3 feet
B. 4 feet
C. 6 feet
D. 10 feet
Rationale: Trap arm length is limited to maintain trap seal integrity.
6. Which material is commonly used for underground drainage
piping?
A. Copper Type L
B. Galvanized steel
, C. PVC SDR 35 or ABS
D. Brass
Rationale: PVC and ABS are corrosion-resistant and approved for
underground drainage.
7. What is the minimum air gap required for potable water
protection?
A. 1/2 inch
B. Pipe diameter
C. Twice the diameter of the outlet or 1 inch minimum
D. 6 inches
Rationale: Air gaps prevent backflow contamination.
8. What device prevents backflow in a water system?
A. Trap
B. Cleanout
C. Backflow preventer
D. Vent stack
Rationale: Backflow preventers stop reverse flow of contaminated
water.
9. What is the purpose of a cleanout?
A. Increase flow
B. Vent sewer gas
C. Provide access for clearing blockages
D. Measure water pressure
Rationale: Cleanouts allow maintenance access to drainage systems.
10. What is the minimum slope for a 4-inch drain pipe?
