South Carolina Residential Plumbing Contractor
Examination (Technical Exam) Questions and
Correct Answers (Verified Answers) Plus Rationale
2027 Q&A| Instant Download Pdf
1. What is the primary purpose of a plumbing trap installed beneath
a fixture?
A. Increase water pressure
B. Prevent sewer gases from entering the building
C. Increase drainage velocity
D. Reduce the fixture's water consumption
Answer: B. Prevent sewer gases from entering the building
Rationale: A plumbing trap maintains a water seal between the
fixture and the drainage system. This water seal prevents sewer gases
and odors from entering occupied areas of the building.
2. Which fitting is commonly used to change the direction of a
drainage pipe by approximately 90 degrees?
,A. Coupling
B. Union
C. Elbow
D. Bushing
Answer: C. Elbow
Rationale: An elbow is designed to change the direction of piping. In
drainage systems, long-sweep elbows are commonly preferred where
appropriate because they provide smoother flow and reduce the
likelihood of blockages.
3. What is the primary function of a plumbing vent system?
A. Supply hot water to fixtures
B. Increase water pressure
C. Protect trap seals and allow proper drainage-system airflow
D. Filter wastewater
Answer: C. Protect trap seals and allow proper drainage-system
airflow
Rationale: Venting allows air to enter the drainage system and helps
equalize pressure. Proper venting protects trap seals from siphonage
and backpressure while allowing wastewater to drain efficiently.
, 4. Which material is commonly used for residential sanitary drainage
piping?
A. PVC
B. Aluminum foil
C. Galvanized sheet metal only
D. Glass tubing
Answer: A. PVC
Rationale: PVC is widely used for sanitary drainage, waste, and vent
piping because it is corrosion-resistant, relatively lightweight, and
easy to install when permitted by the applicable plumbing code.
5. What does DWV stand for?
A. Domestic Water Valve
B. Drain, Waste, and Vent
C. Drain Water Volume
D. Domestic Waste Vacuum
Answer: B. Drain, Waste, and Vent
Rationale: DWV refers to the portion of a plumbing system
responsible for carrying wastewater away from fixtures and providing
venting to maintain proper drainage-system operation.
6. What is the purpose of a cleanout in a drainage system?
, A. To increase water temperature
B. To provide access for inspection and cleaning of drainage piping
C. To regulate water pressure
D. To prevent water from entering the building
Answer: B. To provide access for inspection and cleaning of drainage
piping
Rationale: Cleanouts provide accessible openings into drainage
piping. They allow plumbers to inspect, maintain, and clear
obstructions without unnecessarily removing piping or fixtures.
7. Which device is designed to prevent contaminated water from
flowing backward into the potable water supply?
A. Pressure gauge
B. Backflow prevention device
C. Water heater
D. Drain trap
Answer: B. Backflow prevention device
Rationale: Backflow prevention devices protect potable water from
contamination caused by reverse flow. The appropriate device
depends on the type and degree of backflow hazard.
Examination (Technical Exam) Questions and
Correct Answers (Verified Answers) Plus Rationale
2027 Q&A| Instant Download Pdf
1. What is the primary purpose of a plumbing trap installed beneath
a fixture?
A. Increase water pressure
B. Prevent sewer gases from entering the building
C. Increase drainage velocity
D. Reduce the fixture's water consumption
Answer: B. Prevent sewer gases from entering the building
Rationale: A plumbing trap maintains a water seal between the
fixture and the drainage system. This water seal prevents sewer gases
and odors from entering occupied areas of the building.
2. Which fitting is commonly used to change the direction of a
drainage pipe by approximately 90 degrees?
,A. Coupling
B. Union
C. Elbow
D. Bushing
Answer: C. Elbow
Rationale: An elbow is designed to change the direction of piping. In
drainage systems, long-sweep elbows are commonly preferred where
appropriate because they provide smoother flow and reduce the
likelihood of blockages.
3. What is the primary function of a plumbing vent system?
A. Supply hot water to fixtures
B. Increase water pressure
C. Protect trap seals and allow proper drainage-system airflow
D. Filter wastewater
Answer: C. Protect trap seals and allow proper drainage-system
airflow
Rationale: Venting allows air to enter the drainage system and helps
equalize pressure. Proper venting protects trap seals from siphonage
and backpressure while allowing wastewater to drain efficiently.
, 4. Which material is commonly used for residential sanitary drainage
piping?
A. PVC
B. Aluminum foil
C. Galvanized sheet metal only
D. Glass tubing
Answer: A. PVC
Rationale: PVC is widely used for sanitary drainage, waste, and vent
piping because it is corrosion-resistant, relatively lightweight, and
easy to install when permitted by the applicable plumbing code.
5. What does DWV stand for?
A. Domestic Water Valve
B. Drain, Waste, and Vent
C. Drain Water Volume
D. Domestic Waste Vacuum
Answer: B. Drain, Waste, and Vent
Rationale: DWV refers to the portion of a plumbing system
responsible for carrying wastewater away from fixtures and providing
venting to maintain proper drainage-system operation.
6. What is the purpose of a cleanout in a drainage system?
, A. To increase water temperature
B. To provide access for inspection and cleaning of drainage piping
C. To regulate water pressure
D. To prevent water from entering the building
Answer: B. To provide access for inspection and cleaning of drainage
piping
Rationale: Cleanouts provide accessible openings into drainage
piping. They allow plumbers to inspect, maintain, and clear
obstructions without unnecessarily removing piping or fixtures.
7. Which device is designed to prevent contaminated water from
flowing backward into the potable water supply?
A. Pressure gauge
B. Backflow prevention device
C. Water heater
D. Drain trap
Answer: B. Backflow prevention device
Rationale: Backflow prevention devices protect potable water from
contamination caused by reverse flow. The appropriate device
depends on the type and degree of backflow hazard.
