Journeyman Plumber License Exam 2
Questions And Correct Answers (Verified
Answers) Plus Rationales 2025
1. What is the minimum pipe size allowed for a residential water supply line?
A) 1/2 inch
B) 3/4 inch
C) 1 inch
D) 1 1/4 inch
Answer: B) 3/4 inch
Rationale: Most plumbing codes require a minimum of 3/4 inch pipe for water
supply lines in residential buildings to ensure adequate flow and pressure.
2. What type of valve is commonly used to shut off water supply to a single
fixture?
A) Gate valve
B) Ball valve
C) Check valve
D) Angle stop valve
,Answer: D) Angle stop valve
Rationale: An angle stop valve is typically installed under sinks or toilets to allow
individual fixture shutoff without affecting the entire system.
3. Which material is NOT typically approved for use in potable water piping?
A) Copper
B) CPVC
C) PEX
D) PVC (Schedule 40)
Answer: D) PVC (Schedule 40)
Rationale: Schedule 40 PVC is generally not approved for potable water inside
buildings due to potential chemical leaching; CPVC or PEX is preferred for hot and
cold potable water lines.
4. What is the minimum slope required for a 3-inch horizontal drainage pipe?
A) 1/8 inch per foot
B) 1/4 inch per foot
C) 1/8 to 1/4 inch per foot
D) 1/2 inch per foot
Answer: C) 1/8 to 1/4 inch per foot
Rationale: Plumbing codes specify a slope between 1/8 and 1/4 inch per foot to
ensure proper drainage and prevent sewer gases from escaping.
, 5. Which device prevents backflow and contamination of the potable water
supply?
A) Pressure regulator
B) Backflow preventer
C) Check valve
D) Expansion tank
Answer: B) Backflow preventer
Rationale: A backflow preventer is designed to stop contaminated water from
flowing backward into the clean water supply, protecting public health.
6. When installing a water heater, what is the minimum clearance required from
combustible materials?
A) 1 inch
B) 3 inches
C) 6 inches
D) 18 inches
Answer: D) 18 inches
Rationale: Most codes require a minimum of 18 inches clearance between the
water heater and combustible materials for safety and to prevent fire hazards.
7. What is the purpose of a vent in a plumbing system?
A) To increase water pressure
B) To prevent siphoning of traps
Questions And Correct Answers (Verified
Answers) Plus Rationales 2025
1. What is the minimum pipe size allowed for a residential water supply line?
A) 1/2 inch
B) 3/4 inch
C) 1 inch
D) 1 1/4 inch
Answer: B) 3/4 inch
Rationale: Most plumbing codes require a minimum of 3/4 inch pipe for water
supply lines in residential buildings to ensure adequate flow and pressure.
2. What type of valve is commonly used to shut off water supply to a single
fixture?
A) Gate valve
B) Ball valve
C) Check valve
D) Angle stop valve
,Answer: D) Angle stop valve
Rationale: An angle stop valve is typically installed under sinks or toilets to allow
individual fixture shutoff without affecting the entire system.
3. Which material is NOT typically approved for use in potable water piping?
A) Copper
B) CPVC
C) PEX
D) PVC (Schedule 40)
Answer: D) PVC (Schedule 40)
Rationale: Schedule 40 PVC is generally not approved for potable water inside
buildings due to potential chemical leaching; CPVC or PEX is preferred for hot and
cold potable water lines.
4. What is the minimum slope required for a 3-inch horizontal drainage pipe?
A) 1/8 inch per foot
B) 1/4 inch per foot
C) 1/8 to 1/4 inch per foot
D) 1/2 inch per foot
Answer: C) 1/8 to 1/4 inch per foot
Rationale: Plumbing codes specify a slope between 1/8 and 1/4 inch per foot to
ensure proper drainage and prevent sewer gases from escaping.
, 5. Which device prevents backflow and contamination of the potable water
supply?
A) Pressure regulator
B) Backflow preventer
C) Check valve
D) Expansion tank
Answer: B) Backflow preventer
Rationale: A backflow preventer is designed to stop contaminated water from
flowing backward into the clean water supply, protecting public health.
6. When installing a water heater, what is the minimum clearance required from
combustible materials?
A) 1 inch
B) 3 inches
C) 6 inches
D) 18 inches
Answer: D) 18 inches
Rationale: Most codes require a minimum of 18 inches clearance between the
water heater and combustible materials for safety and to prevent fire hazards.
7. What is the purpose of a vent in a plumbing system?
A) To increase water pressure
B) To prevent siphoning of traps
