ICC Commercial Plumbing Inspector
Exam (P2) Practice Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
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1. Which of the following is the minimum required slope for a 3-inch
horizontal sanitary drainage pipe?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/8 inch per foot for pipes 4 inches or smaller
D. 1/2 inch per foot
Rationale: Horizontal drainage pipes 4 inches or smaller must have a
minimum slope of 1/4 inch per foot; 3-inch pipes specifically follow
1/8 inch per foot minimum.
,2. What is the maximum distance a fixture trap can be from the vent for
a 1 1/2-inch pipe?
A. 3 feet
B. 5 feet
C. 5 feet
D. 6 feet
Rationale: According to plumbing codes, the maximum distance from
a trap to its vent is 5 feet for a 1 1/2-inch pipe.
3. Which material is NOT allowed for underground sanitary sewer piping
in commercial buildings?
A. PVC
B. Copper
C. Cast iron
D. ABS
Rationale: Copper is not typically approved for underground sanitary
drainage due to corrosion concerns and cost; PVC, ABS, and cast iron
are acceptable.
4. What is the minimum water supply pipe size to a commercial water
closet?
A. 1/2 inch
B. 3/4 inch
C. 1 inch
D. 1 1/2 inches
, Rationale: Commercial water closets require at least a 1-inch supply
line to maintain adequate flow and pressure.
5. In commercial plumbing, what is the minimum required air gap
between a potable water supply and a fixture?
A. 1 inch
B. 2 times the diameter of the supply pipe
C. 4 inches
D. 6 inches
Rationale: An air gap must be at least twice the diameter of the
supply pipe to prevent backflow contamination.
6. Which type of trap is required for a floor drain in a commercial
restroom?
A. S-trap
B. P-trap
C. Drum trap
D. Bell trap
Rationale: A P-trap is standard for floor drains to prevent sewer
gases from entering the building while maintaining proper drainage.
7. What is the maximum distance allowed from a water closet to a vent?
A. 2 feet
B. 3 feet
C. 5 feet
D. 6 feet
, Rationale: Plumbing codes specify a maximum trap arm length of 6
feet for a water closet vent to ensure proper venting and prevent
siphoning.
8. Which of the following is an acceptable method to vent a commercial
sink?
A. Loop vent
B. Wet vent
C. S-trap vent
D. None of the above
Rationale: Wet venting is allowed for commercial sinks in accordance
with the plumbing code, where one pipe serves as a vent for multiple
fixtures.
9. What is the minimum slope for a 6-inch horizontal sanitary sewer line?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 1/8 inch per foot
Rationale: Large-diameter pipes (6 inches or more) require a
minimum slope of 1/8 inch per foot to maintain proper flow.
10. Which device is required to prevent backflow in a commercial
irrigation system?
A. Vacuum breaker
B. Reduced pressure zone assembly (RPZ)
Exam (P2) Practice Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
1. Which of the following is the minimum required slope for a 3-inch
horizontal sanitary drainage pipe?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/8 inch per foot for pipes 4 inches or smaller
D. 1/2 inch per foot
Rationale: Horizontal drainage pipes 4 inches or smaller must have a
minimum slope of 1/4 inch per foot; 3-inch pipes specifically follow
1/8 inch per foot minimum.
,2. What is the maximum distance a fixture trap can be from the vent for
a 1 1/2-inch pipe?
A. 3 feet
B. 5 feet
C. 5 feet
D. 6 feet
Rationale: According to plumbing codes, the maximum distance from
a trap to its vent is 5 feet for a 1 1/2-inch pipe.
3. Which material is NOT allowed for underground sanitary sewer piping
in commercial buildings?
A. PVC
B. Copper
C. Cast iron
D. ABS
Rationale: Copper is not typically approved for underground sanitary
drainage due to corrosion concerns and cost; PVC, ABS, and cast iron
are acceptable.
4. What is the minimum water supply pipe size to a commercial water
closet?
A. 1/2 inch
B. 3/4 inch
C. 1 inch
D. 1 1/2 inches
, Rationale: Commercial water closets require at least a 1-inch supply
line to maintain adequate flow and pressure.
5. In commercial plumbing, what is the minimum required air gap
between a potable water supply and a fixture?
A. 1 inch
B. 2 times the diameter of the supply pipe
C. 4 inches
D. 6 inches
Rationale: An air gap must be at least twice the diameter of the
supply pipe to prevent backflow contamination.
6. Which type of trap is required for a floor drain in a commercial
restroom?
A. S-trap
B. P-trap
C. Drum trap
D. Bell trap
Rationale: A P-trap is standard for floor drains to prevent sewer
gases from entering the building while maintaining proper drainage.
7. What is the maximum distance allowed from a water closet to a vent?
A. 2 feet
B. 3 feet
C. 5 feet
D. 6 feet
, Rationale: Plumbing codes specify a maximum trap arm length of 6
feet for a water closet vent to ensure proper venting and prevent
siphoning.
8. Which of the following is an acceptable method to vent a commercial
sink?
A. Loop vent
B. Wet vent
C. S-trap vent
D. None of the above
Rationale: Wet venting is allowed for commercial sinks in accordance
with the plumbing code, where one pipe serves as a vent for multiple
fixtures.
9. What is the minimum slope for a 6-inch horizontal sanitary sewer line?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 1/8 inch per foot
Rationale: Large-diameter pipes (6 inches or more) require a
minimum slope of 1/8 inch per foot to maintain proper flow.
10. Which device is required to prevent backflow in a commercial
irrigation system?
A. Vacuum breaker
B. Reduced pressure zone assembly (RPZ)
