California Contractor License
Examination Plumbing with Practice
Questions And Correct An
1. In a 12-story high-rise, a 4-inch vertical soil stack serving 60 water closets on floors
2-12 must be tested. According to the California Plumbing Code, which test method is
required for the entire stack before concealment?
A. Water test with 10 ft head at the lowest point for 15 minutes
B. Air test at 5 psi for 15 minutes
C. Water test with 10 ft head at the highest point for 15 minutes
D. Smoke test with visual inspection
Answer: A. Water test with 10 ft head at the lowest point for 15 minutes
Rationale: The California Plumbing Code (CPC) requires a water test with a minimum
10-foot head at the lowest point for at least 15 minutes for drainage systems. Air tests are
not permitted for final acceptance in this context. Smoke tests are for existing systems, not
new construction.
2. A plumbing contractor submits a bid for a public works project in California.
Which prevailing wage requirement applies to apprentices on the job?
A. Apprentices must be paid the journeyman rate if they perform journeyman tasks.
B. Apprentices must be registered in a state-approved program and paid the applicable
apprentice rate.
C. Apprentices can be paid trainee wages regardless of registration.
D. Apprentices are exempt from prevailing wage if supervised.
Answer: B. Apprentices must be registered in a state-approved program and paid the
applicable apprentice rate.
Rationale: California prevailing wage law requires apprentices to be registered in a
state-approved apprenticeship program and paid the corresponding apprentice wage rate.
Paying journeyman rate is not required if properly classified. Exemptions do not apply
based on supervision.
Page 1 of 80
,3. A commercial kitchen requires a grease interceptor. The discharge from a
3-compartment sink and a dishwasher flows into the interceptor. What is the
minimum required capacity according to the CPC?
A. Based on total volume of fixtures draining into it
B. Based on the flow rate of the largest fixture
C. Based on the combined flow rate of all fixtures
D. Based on the number of fixtures connected
Answer: C. Based on the combined flow rate of all fixtures
Rationale: The CPC requires grease interceptor sizing based on the combined flow rate of
all fixtures discharging into it, considering simultaneous use. Volume-based or
largest-fixture methods are insufficient. Number of fixtures alone does not determine
capacity.
4. A solar water heating system is installed on a roof with a 30-degree pitch. The
collector must be protected from freezing. Which freeze protection method is most
appropriate for a closed-loop system in a freeze-prone area?
A. Recirculation of domestic water
B. Use of propylene glycol antifreeze
C. Manual drain-down at night
D. Electric heat tape on exposed pipes
Answer: B. Use of propylene glycol antifreeze
Rationale: Closed-loop solar systems in freeze-prone areas typically use propylene glycol
as a heat transfer fluid to prevent freezing. Recirculation wastes water and is not for closed
loops. Manual drain-down is impractical, and heat tape is insufficient for collector
protection.
Page 2 of 80
,5. A plumbing contractor is installing a backflow prevention assembly on a fire
sprinkler system connected to a potable water supply. Which type of assembly is
required by the CPC for this high-hazard application?
A. Double check valve assembly
B. Reduced pressure principle assembly
C. Atmospheric vacuum breaker
D. Pressure vacuum breaker
Answer: B. Reduced pressure principle assembly
Rationale: Fire sprinkler systems are considered high hazard due to chemicals and
stagnation. The CPC requires a reduced pressure principle assembly for high-hazard
connections. Double check and vacuum breakers are for lower hazard or specific uses.
6. When calculating the water supply fixture units (WSFU) for a building, a plumbing
contractor must account for a flushometer valve water closet. What is the WSFU value
for a flushometer valve water closet in the CPC?
A. 2.5
B. 5
C. 10
D. 1
Answer: C. 10
Rationale: The CPC assigns a WSFU of 10 for a flushometer valve water closet, reflecting
its higher demand. Other values correspond to different fixtures. This is critical for sizing
water supply piping.
Page 3 of 80
, 7. A contractor is installing a new water heater in a garage. The heater is elevated 18
inches above the floor. What additional safety requirement does the CPC mandate for
this installation?
A. A drip pan with drain
B. A seismic strapping kit
C. A pressure relief valve
D. A thermal expansion tank
Answer: B. A seismic strapping kit
Rationale: In California, water heaters in garages must be elevated to protect from vehicle
impact and must be strapped to resist seismic movement. A drip pan is not required in a
garage. Pressure relief and expansion tanks are separate requirements.
8. A plumbing contractor is designing a drainage system for a building with a 4-inch
building drain. What is the maximum allowable slope for a 4-inch horizontal drain
according to the CPC?
A. 1/4 inch per foot
B. 1/2 inch per foot
C. 1/8 inch per foot
D. 1 inch per foot
Answer: B. 1/2 inch per foot
Rationale: The CPC allows a maximum slope of 1/2 inch per foot for 4-inch horizontal
drains to ensure proper flow without excessive velocity. Minimum slope is 1/4 inch per foot.
Larger slopes may cause solids to separate.
Page 4 of 80
Examination Plumbing with Practice
Questions And Correct An
1. In a 12-story high-rise, a 4-inch vertical soil stack serving 60 water closets on floors
2-12 must be tested. According to the California Plumbing Code, which test method is
required for the entire stack before concealment?
A. Water test with 10 ft head at the lowest point for 15 minutes
B. Air test at 5 psi for 15 minutes
C. Water test with 10 ft head at the highest point for 15 minutes
D. Smoke test with visual inspection
Answer: A. Water test with 10 ft head at the lowest point for 15 minutes
Rationale: The California Plumbing Code (CPC) requires a water test with a minimum
10-foot head at the lowest point for at least 15 minutes for drainage systems. Air tests are
not permitted for final acceptance in this context. Smoke tests are for existing systems, not
new construction.
2. A plumbing contractor submits a bid for a public works project in California.
Which prevailing wage requirement applies to apprentices on the job?
A. Apprentices must be paid the journeyman rate if they perform journeyman tasks.
B. Apprentices must be registered in a state-approved program and paid the applicable
apprentice rate.
C. Apprentices can be paid trainee wages regardless of registration.
D. Apprentices are exempt from prevailing wage if supervised.
Answer: B. Apprentices must be registered in a state-approved program and paid the
applicable apprentice rate.
Rationale: California prevailing wage law requires apprentices to be registered in a
state-approved apprenticeship program and paid the corresponding apprentice wage rate.
Paying journeyman rate is not required if properly classified. Exemptions do not apply
based on supervision.
Page 1 of 80
,3. A commercial kitchen requires a grease interceptor. The discharge from a
3-compartment sink and a dishwasher flows into the interceptor. What is the
minimum required capacity according to the CPC?
A. Based on total volume of fixtures draining into it
B. Based on the flow rate of the largest fixture
C. Based on the combined flow rate of all fixtures
D. Based on the number of fixtures connected
Answer: C. Based on the combined flow rate of all fixtures
Rationale: The CPC requires grease interceptor sizing based on the combined flow rate of
all fixtures discharging into it, considering simultaneous use. Volume-based or
largest-fixture methods are insufficient. Number of fixtures alone does not determine
capacity.
4. A solar water heating system is installed on a roof with a 30-degree pitch. The
collector must be protected from freezing. Which freeze protection method is most
appropriate for a closed-loop system in a freeze-prone area?
A. Recirculation of domestic water
B. Use of propylene glycol antifreeze
C. Manual drain-down at night
D. Electric heat tape on exposed pipes
Answer: B. Use of propylene glycol antifreeze
Rationale: Closed-loop solar systems in freeze-prone areas typically use propylene glycol
as a heat transfer fluid to prevent freezing. Recirculation wastes water and is not for closed
loops. Manual drain-down is impractical, and heat tape is insufficient for collector
protection.
Page 2 of 80
,5. A plumbing contractor is installing a backflow prevention assembly on a fire
sprinkler system connected to a potable water supply. Which type of assembly is
required by the CPC for this high-hazard application?
A. Double check valve assembly
B. Reduced pressure principle assembly
C. Atmospheric vacuum breaker
D. Pressure vacuum breaker
Answer: B. Reduced pressure principle assembly
Rationale: Fire sprinkler systems are considered high hazard due to chemicals and
stagnation. The CPC requires a reduced pressure principle assembly for high-hazard
connections. Double check and vacuum breakers are for lower hazard or specific uses.
6. When calculating the water supply fixture units (WSFU) for a building, a plumbing
contractor must account for a flushometer valve water closet. What is the WSFU value
for a flushometer valve water closet in the CPC?
A. 2.5
B. 5
C. 10
D. 1
Answer: C. 10
Rationale: The CPC assigns a WSFU of 10 for a flushometer valve water closet, reflecting
its higher demand. Other values correspond to different fixtures. This is critical for sizing
water supply piping.
Page 3 of 80
, 7. A contractor is installing a new water heater in a garage. The heater is elevated 18
inches above the floor. What additional safety requirement does the CPC mandate for
this installation?
A. A drip pan with drain
B. A seismic strapping kit
C. A pressure relief valve
D. A thermal expansion tank
Answer: B. A seismic strapping kit
Rationale: In California, water heaters in garages must be elevated to protect from vehicle
impact and must be strapped to resist seismic movement. A drip pan is not required in a
garage. Pressure relief and expansion tanks are separate requirements.
8. A plumbing contractor is designing a drainage system for a building with a 4-inch
building drain. What is the maximum allowable slope for a 4-inch horizontal drain
according to the CPC?
A. 1/4 inch per foot
B. 1/2 inch per foot
C. 1/8 inch per foot
D. 1 inch per foot
Answer: B. 1/2 inch per foot
Rationale: The CPC allows a maximum slope of 1/2 inch per foot for 4-inch horizontal
drains to ensure proper flow without excessive velocity. Minimum slope is 1/4 inch per foot.
Larger slopes may cause solids to separate.
Page 4 of 80
