NC Plumbing, Heating & Fire Sprinkler Contractors
Board – Plumbing Contractor Examination
(Unlimited) Questions and Correct Answers
(Verified Answers) Plus Rationale 2027 Q&A|
Instant Download Pdf
1. What is the primary purpose of a plumbing trap?
A. To increase water pressure
B. To prevent pipe corrosion
C. To prevent sewer gases from entering the building
D. To increase drainage velocity
Answer: C. To prevent sewer gases from entering the building
Rationale: A plumbing trap retains a water seal that separates the
building's occupied space from the sanitary drainage system. The
water seal prevents sewer gases and odors from entering the building
while still allowing wastewater to drain.
,2. Which fitting is generally preferred when changing the direction of
flow in a horizontal sanitary drainage line?
A. Sanitary tee
B. Wye
C. Straight tee
D. Coupling
Answer: B. Wye
Rationale: A wye provides a smoother transition for wastewater
entering or changing direction in a drainage system. Its angled branch
reduces turbulence and the likelihood of obstruction compared with a
conventional straight tee.
3. What is the primary function of a plumbing vent system?
A. Increase water pressure
B. Supply potable water
C. Protect trap seals and allow proper drainage airflow
D. Reduce hot-water temperature
Answer: C. Protect trap seals and allow proper drainage airflow
Rationale: Venting allows air to enter and leave the drainage system
so pressure fluctuations do not siphon or blow out trap seals. Proper
,venting also promotes efficient drainage by allowing the system to
operate at approximately atmospheric pressure.
4. A plumbing fixture that discharges wastewater through an air gap
into a receptor is using what type of waste connection?
A. Direct waste
B. Indirect waste
C. Pressure waste
D. Backflow waste
Answer: B. Indirect waste
Rationale: An indirect waste connection discharges through an air gap
or other approved method into a receptor rather than connecting
directly to the sanitary drainage piping. This arrangement is
commonly used where protection against contamination or sewer-gas
transmission is important.
5. What is the main purpose of a cleanout?
A. To regulate water pressure
B. To provide access for inspection and clearing of drainage piping
, C. To prevent water hammer
D. To provide additional venting
Answer: B. To provide access for inspection and clearing of drainage
piping
Rationale: Cleanouts provide access to drainage piping so blockages
can be located and removed. They are especially important at
locations where changes in direction or other conditions make
maintenance necessary.
6. Which device is specifically designed to prevent contaminated
water from flowing backward into the potable water supply?
A. Pressure-reducing valve
B. Backflow prevention assembly
C. Gate valve
D. Balancing valve
Answer: B. Backflow prevention assembly
Rationale: Backflow prevention devices protect the potable water
system from contamination caused by backsiphonage or
backpressure. The specific device required depends on the degree and
type of hazard.
Board – Plumbing Contractor Examination
(Unlimited) Questions and Correct Answers
(Verified Answers) Plus Rationale 2027 Q&A|
Instant Download Pdf
1. What is the primary purpose of a plumbing trap?
A. To increase water pressure
B. To prevent pipe corrosion
C. To prevent sewer gases from entering the building
D. To increase drainage velocity
Answer: C. To prevent sewer gases from entering the building
Rationale: A plumbing trap retains a water seal that separates the
building's occupied space from the sanitary drainage system. The
water seal prevents sewer gases and odors from entering the building
while still allowing wastewater to drain.
,2. Which fitting is generally preferred when changing the direction of
flow in a horizontal sanitary drainage line?
A. Sanitary tee
B. Wye
C. Straight tee
D. Coupling
Answer: B. Wye
Rationale: A wye provides a smoother transition for wastewater
entering or changing direction in a drainage system. Its angled branch
reduces turbulence and the likelihood of obstruction compared with a
conventional straight tee.
3. What is the primary function of a plumbing vent system?
A. Increase water pressure
B. Supply potable water
C. Protect trap seals and allow proper drainage airflow
D. Reduce hot-water temperature
Answer: C. Protect trap seals and allow proper drainage airflow
Rationale: Venting allows air to enter and leave the drainage system
so pressure fluctuations do not siphon or blow out trap seals. Proper
,venting also promotes efficient drainage by allowing the system to
operate at approximately atmospheric pressure.
4. A plumbing fixture that discharges wastewater through an air gap
into a receptor is using what type of waste connection?
A. Direct waste
B. Indirect waste
C. Pressure waste
D. Backflow waste
Answer: B. Indirect waste
Rationale: An indirect waste connection discharges through an air gap
or other approved method into a receptor rather than connecting
directly to the sanitary drainage piping. This arrangement is
commonly used where protection against contamination or sewer-gas
transmission is important.
5. What is the main purpose of a cleanout?
A. To regulate water pressure
B. To provide access for inspection and clearing of drainage piping
, C. To prevent water hammer
D. To provide additional venting
Answer: B. To provide access for inspection and clearing of drainage
piping
Rationale: Cleanouts provide access to drainage piping so blockages
can be located and removed. They are especially important at
locations where changes in direction or other conditions make
maintenance necessary.
6. Which device is specifically designed to prevent contaminated
water from flowing backward into the potable water supply?
A. Pressure-reducing valve
B. Backflow prevention assembly
C. Gate valve
D. Balancing valve
Answer: B. Backflow prevention assembly
Rationale: Backflow prevention devices protect the potable water
system from contamination caused by backsiphonage or
backpressure. The specific device required depends on the degree and
type of hazard.
