Plumbing Contractor Licensing Exam – Practice Test
Verified Questions, Correct Answers, and Detailed
Explanations for Computer Science Students||Already
Graded A+
1. What is the primary purpose of a plumbing vent system?
A. To increase water pressure
B. To prevent sewer gases from entering the building
C. To heat water
D. To store water
Answer: B
Rationale: Vents allow sewer gases to escape safely and maintain proper air
pressure in the drainage system.
2. Which pipe material is commonly used for potable water supply?
A. PVC
B. CPVC
C. Cast iron
D. Galvanized steel
Answer: B
Rationale: CPVC (chlorinated polyvinyl chloride) is resistant to corrosion and
safe for drinking water.
3. What is the minimum slope required for a 2-inch horizontal drain line?
A. 1/16 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 1 inch per foot
Answer: B
Rationale: A slope of 1/4 inch per foot ensures proper drainage and prevents
clogging.
4. Which tool is used to remove a P-trap?
A. Pipe wrench
B. Basin wrench
,C. Plunger
D. Adjustable wrench
Answer: D
Rationale: An adjustable wrench is typically used to loosen slip nuts on P-traps.
5. What is the purpose of a backflow preventer?
A. To increase water pressure
B. To prevent water from flowing backward into the potable system
C. To heat water
D. To reduce water temperature
Answer: B
Rationale: Backflow preventers protect drinking water from contamination due
to reverse flow.
6. Which type of water heater uses electricity to heat water?
A. Tankless gas heater
B. Tank electric heater
C. Solar heater
D. Indirect boiler
Answer: B
Rationale: Tank electric water heaters rely on electric heating elements to
warm stored water.
7. What is the maximum distance a trap can be from a vent for a 1.5-inch
drain?
A. 2 feet
B. 3 feet
C. 5 feet
D. 6 feet
Answer: C
Rationale: Plumbing codes limit the distance to ensure proper venting and
prevent siphoning of the trap.
8. What is the primary function of a water hammer arrestor?
A. Prevent leaks
B. Reduce water pressure
C. Absorb shock from sudden water flow
D. Heat water
, Answer: C
Rationale: Water hammer arrestors prevent pipes from banging due to sudden
valve closure.
9. Which type of valve is typically used to shut off water supply to a fixture?
A. Ball valve
B. Check valve
C. Relief valve
D. Butterfly valve
Answer: A
Rationale: Ball valves provide a reliable shutoff for individual fixtures.
10. What does the term “DWV” stand for in plumbing?
A. Domestic Water Valve
B. Drain, Waste, and Vent
C. Direct Water Volume
D. Drainage Water Valve
Answer: B
Rationale: DWV systems handle drainage, waste removal, and venting without
pressurized water.
11. Which pipe joining method is commonly used for copper piping?
A. Solvent welding
B. Threading
C. Soldering
D. Compression fitting only
Answer: C
Rationale: Soldering provides a secure, leak-proof connection for copper pipes.
12. Which fixture requires an air gap to prevent contamination?
A. Toilet
B. Laundry sink
C. Kitchen sink
D. Bathtub
Answer: C
Rationale: Air gaps prevent backflow of contaminated water into potable water
lines.
13. What is the purpose of a pressure-reducing valve?
Verified Questions, Correct Answers, and Detailed
Explanations for Computer Science Students||Already
Graded A+
1. What is the primary purpose of a plumbing vent system?
A. To increase water pressure
B. To prevent sewer gases from entering the building
C. To heat water
D. To store water
Answer: B
Rationale: Vents allow sewer gases to escape safely and maintain proper air
pressure in the drainage system.
2. Which pipe material is commonly used for potable water supply?
A. PVC
B. CPVC
C. Cast iron
D. Galvanized steel
Answer: B
Rationale: CPVC (chlorinated polyvinyl chloride) is resistant to corrosion and
safe for drinking water.
3. What is the minimum slope required for a 2-inch horizontal drain line?
A. 1/16 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 1 inch per foot
Answer: B
Rationale: A slope of 1/4 inch per foot ensures proper drainage and prevents
clogging.
4. Which tool is used to remove a P-trap?
A. Pipe wrench
B. Basin wrench
,C. Plunger
D. Adjustable wrench
Answer: D
Rationale: An adjustable wrench is typically used to loosen slip nuts on P-traps.
5. What is the purpose of a backflow preventer?
A. To increase water pressure
B. To prevent water from flowing backward into the potable system
C. To heat water
D. To reduce water temperature
Answer: B
Rationale: Backflow preventers protect drinking water from contamination due
to reverse flow.
6. Which type of water heater uses electricity to heat water?
A. Tankless gas heater
B. Tank electric heater
C. Solar heater
D. Indirect boiler
Answer: B
Rationale: Tank electric water heaters rely on electric heating elements to
warm stored water.
7. What is the maximum distance a trap can be from a vent for a 1.5-inch
drain?
A. 2 feet
B. 3 feet
C. 5 feet
D. 6 feet
Answer: C
Rationale: Plumbing codes limit the distance to ensure proper venting and
prevent siphoning of the trap.
8. What is the primary function of a water hammer arrestor?
A. Prevent leaks
B. Reduce water pressure
C. Absorb shock from sudden water flow
D. Heat water
, Answer: C
Rationale: Water hammer arrestors prevent pipes from banging due to sudden
valve closure.
9. Which type of valve is typically used to shut off water supply to a fixture?
A. Ball valve
B. Check valve
C. Relief valve
D. Butterfly valve
Answer: A
Rationale: Ball valves provide a reliable shutoff for individual fixtures.
10. What does the term “DWV” stand for in plumbing?
A. Domestic Water Valve
B. Drain, Waste, and Vent
C. Direct Water Volume
D. Drainage Water Valve
Answer: B
Rationale: DWV systems handle drainage, waste removal, and venting without
pressurized water.
11. Which pipe joining method is commonly used for copper piping?
A. Solvent welding
B. Threading
C. Soldering
D. Compression fitting only
Answer: C
Rationale: Soldering provides a secure, leak-proof connection for copper pipes.
12. Which fixture requires an air gap to prevent contamination?
A. Toilet
B. Laundry sink
C. Kitchen sink
D. Bathtub
Answer: C
Rationale: Air gaps prevent backflow of contaminated water into potable water
lines.
13. What is the purpose of a pressure-reducing valve?
