COLORADO ICC RESIDENTIAL PLUMBING
INSPECTOR EXAM QUESTIONS AND CORRECT
ANSWERS (VERIFIED ANSWERS) Q&A 2026
|INSTANT DOWNLOAD PDF
1. What is the primary purpose of a plumbing trap?
A. Increase water pressure
B. Prevent sewer gases from entering the building
C. Increase flow rate
D. Filter solids from wastewater
Correct Answer: B
Rationale: A trap retains a water seal that blocks sewer gases
from backing into occupied spaces.
2. The minimum trap seal depth is typically:
A. 1 inch
B. 2 inches
C. 4 inches
D. 6 inches
Correct Answer: B
Rationale: Most plumbing codes require a trap seal between 2
and 4 inches, with 2 inches commonly accepted minimum.
,3. What is the purpose of a vent system in plumbing?
A. Increase water pressure
B. Allow sewer gases to enter the building
C. Prevent trap siphonage and allow air circulation
D. Drain wastewater faster
Correct Answer: C
Rationale: Venting prevents negative pressure that could
siphon trap seals and allows air movement in the drainage
system.
4. What is the minimum slope for a horizontal drainage pipe 3
inches or less in diameter?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 1 inch per foot
Correct Answer: B
Rationale: ICC codes typically require 1/4 inch per foot slope
for pipes 3 inches or less.
5. Which fixture is required to be vented?
A. Only toilets
B. Only sinks
,C. All plumbing fixtures connected to drainage systems
D. Only showers
Correct Answer: C
Rationale: All fixtures connected to the drainage system must
be properly vented to prevent siphonage.
6. What is the function of a cleanout?
A. Increase drainage speed
B. Provide access for cleaning blockages in piping
C. Prevent backflow
D. Seal pipe joints
Correct Answer: B
Rationale: Cleanouts allow access to remove obstructions in
drainage piping systems.
7. The minimum distance between a trap and its vent is
governed to prevent:
A. Excess pressure
B. Trap siphonage
C. Pipe corrosion
D. Excess flow velocity
Correct Answer: B
Rationale: If the vent is too far from the trap, siphonage can
occur and break the water seal.
, 8. A water hammer is best described as:
A. Slow water flow in pipes
B. Pressure surge when water flow is suddenly stopped
C. Air trapped in vents
D. Pipe corrosion due to minerals
Correct Answer: B
Rationale: Water hammer occurs when moving water is
abruptly stopped, creating a pressure shock wave.
9. The minimum diameter for a building sewer in residential
construction is typically:
A. 2 inches
B. 3 inches
C. 4 inches
D. 6 inches
Correct Answer: C
Rationale: Most residential codes require a minimum 4-inch
building sewer.
10. Backflow in plumbing systems refers to:
A. Normal water flow
B. Reverse flow of water into potable supply
INSPECTOR EXAM QUESTIONS AND CORRECT
ANSWERS (VERIFIED ANSWERS) Q&A 2026
|INSTANT DOWNLOAD PDF
1. What is the primary purpose of a plumbing trap?
A. Increase water pressure
B. Prevent sewer gases from entering the building
C. Increase flow rate
D. Filter solids from wastewater
Correct Answer: B
Rationale: A trap retains a water seal that blocks sewer gases
from backing into occupied spaces.
2. The minimum trap seal depth is typically:
A. 1 inch
B. 2 inches
C. 4 inches
D. 6 inches
Correct Answer: B
Rationale: Most plumbing codes require a trap seal between 2
and 4 inches, with 2 inches commonly accepted minimum.
,3. What is the purpose of a vent system in plumbing?
A. Increase water pressure
B. Allow sewer gases to enter the building
C. Prevent trap siphonage and allow air circulation
D. Drain wastewater faster
Correct Answer: C
Rationale: Venting prevents negative pressure that could
siphon trap seals and allows air movement in the drainage
system.
4. What is the minimum slope for a horizontal drainage pipe 3
inches or less in diameter?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 1 inch per foot
Correct Answer: B
Rationale: ICC codes typically require 1/4 inch per foot slope
for pipes 3 inches or less.
5. Which fixture is required to be vented?
A. Only toilets
B. Only sinks
,C. All plumbing fixtures connected to drainage systems
D. Only showers
Correct Answer: C
Rationale: All fixtures connected to the drainage system must
be properly vented to prevent siphonage.
6. What is the function of a cleanout?
A. Increase drainage speed
B. Provide access for cleaning blockages in piping
C. Prevent backflow
D. Seal pipe joints
Correct Answer: B
Rationale: Cleanouts allow access to remove obstructions in
drainage piping systems.
7. The minimum distance between a trap and its vent is
governed to prevent:
A. Excess pressure
B. Trap siphonage
C. Pipe corrosion
D. Excess flow velocity
Correct Answer: B
Rationale: If the vent is too far from the trap, siphonage can
occur and break the water seal.
, 8. A water hammer is best described as:
A. Slow water flow in pipes
B. Pressure surge when water flow is suddenly stopped
C. Air trapped in vents
D. Pipe corrosion due to minerals
Correct Answer: B
Rationale: Water hammer occurs when moving water is
abruptly stopped, creating a pressure shock wave.
9. The minimum diameter for a building sewer in residential
construction is typically:
A. 2 inches
B. 3 inches
C. 4 inches
D. 6 inches
Correct Answer: C
Rationale: Most residential codes require a minimum 4-inch
building sewer.
10. Backflow in plumbing systems refers to:
A. Normal water flow
B. Reverse flow of water into potable supply
