ICC P1 Residential Plumbing Inspector
Exam Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the minimum required slope for a 2-inch horizontal
drainage pipe?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 3/4 inch per foot
B. 1/4 inch per foot
Proper slope ensures adequate gravity drainage and prevents
standing water.
2. Which type of pipe is typically used for underground potable
water lines in residential construction?
A. PVC
B. CPVC
C. PEX
D. Cast iron
A. PVC
PVC is durable, corrosion-resistant, and approved for underground
water service.
,3. A fixture unit (FU) is used to:
A. Measure water pressure
B. Determine pipe size
C. Calculate flow velocity
D. Estimate pipe length
B. Determine pipe size
Fixture units standardize water demand for sizing plumbing
systems.
4. What is the minimum air gap required for a kitchen sink faucet to
prevent backflow?
A. 1 inch
B. 1-1/2 inches
C. 2 inches
D. 3 inches
B. 1-1/2 inches
Air gaps prevent cross-connection and backflow contamination.
5. What is the primary purpose of a vent in a plumbing system?
A. Increase water pressure
B. Remove wastewater
C. Prevent sewer gases from entering the building
D. Support pipes structurally
C. Prevent sewer gases from entering the building
Vents equalize pressure and allow gases to escape safely.
6. The minimum distance a cleanout must extend above finished
grade is:
A. 3 inches
B. 6 inches
, C. 12 inches
D. 18 inches
B. 6 inches
Cleanouts must be accessible for maintenance and inspection.
7. Which material is commonly used for residential water supply
risers inside walls?
A. Copper
B. Cast iron
C. ABS
D. Galvanized steel
A. Copper
Copper is corrosion-resistant, reliable, and widely accepted for
interior plumbing.
8. A trap primer is required when:
A. There is a long branch drain without regular fixture use
B. Installing a new water heater
C. Connecting a water softener
D. Replacing a faucet aerator
A. There is a long branch drain without regular fixture use
Trap primers maintain water seals in seldom-used traps to prevent
sewer gas entry.
9. The maximum length for a 1-1/4 inch trap arm is:
A. 2 feet
B. 3 feet
C. 4 feet
D. 5 feet
Exam Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the minimum required slope for a 2-inch horizontal
drainage pipe?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 3/4 inch per foot
B. 1/4 inch per foot
Proper slope ensures adequate gravity drainage and prevents
standing water.
2. Which type of pipe is typically used for underground potable
water lines in residential construction?
A. PVC
B. CPVC
C. PEX
D. Cast iron
A. PVC
PVC is durable, corrosion-resistant, and approved for underground
water service.
,3. A fixture unit (FU) is used to:
A. Measure water pressure
B. Determine pipe size
C. Calculate flow velocity
D. Estimate pipe length
B. Determine pipe size
Fixture units standardize water demand for sizing plumbing
systems.
4. What is the minimum air gap required for a kitchen sink faucet to
prevent backflow?
A. 1 inch
B. 1-1/2 inches
C. 2 inches
D. 3 inches
B. 1-1/2 inches
Air gaps prevent cross-connection and backflow contamination.
5. What is the primary purpose of a vent in a plumbing system?
A. Increase water pressure
B. Remove wastewater
C. Prevent sewer gases from entering the building
D. Support pipes structurally
C. Prevent sewer gases from entering the building
Vents equalize pressure and allow gases to escape safely.
6. The minimum distance a cleanout must extend above finished
grade is:
A. 3 inches
B. 6 inches
, C. 12 inches
D. 18 inches
B. 6 inches
Cleanouts must be accessible for maintenance and inspection.
7. Which material is commonly used for residential water supply
risers inside walls?
A. Copper
B. Cast iron
C. ABS
D. Galvanized steel
A. Copper
Copper is corrosion-resistant, reliable, and widely accepted for
interior plumbing.
8. A trap primer is required when:
A. There is a long branch drain without regular fixture use
B. Installing a new water heater
C. Connecting a water softener
D. Replacing a faucet aerator
A. There is a long branch drain without regular fixture use
Trap primers maintain water seals in seldom-used traps to prevent
sewer gas entry.
9. The maximum length for a 1-1/4 inch trap arm is:
A. 2 feet
B. 3 feet
C. 4 feet
D. 5 feet
