Texas Journeyman Plumber
Examination Questions And Correct
Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
1. Which component prevents contaminated water from flowing
backward into a potable water supply?
A. Cleanout
B. Trap primer
C. Backflow prevention device
D. Expansion tank
Answer: C. Backflow prevention device
Rationale: A backflow prevention device is specifically designed to
protect potable water from contamination caused by backpressure or
backsiphonage.
2. What is the primary purpose of a plumbing trap?
A. Increase water pressure
B. Prevent sewer gases from entering a building
C. Increase drainage velocity
D. Reduce water temperature
Answer: B. Prevent sewer gases from entering a building
,Rationale: A properly installed trap maintains a water seal that
prevents gases from the drainage system from entering occupied
spaces.
3. Which fitting is normally used to change the direction of a
drainage pipe while maintaining proper flow?
A. Sanitary tee
B. Drainage elbow
C. Coupling
D. Union
Answer: B. Drainage elbow
Rationale: Drainage-pattern elbows provide a smoother transition and
are intended to direct waste flow without creating unnecessary
turbulence.
4. What is the principal purpose of a cleanout?
A. Measure water pressure
B. Provide access for cleaning a drainage system
C. Prevent thermal expansion
D. Control fixture temperature
Answer: B. Provide access for cleaning a drainage system
Rationale: A cleanout provides an accessible opening through which
approved equipment can be inserted to clear obstructions from
drainage piping.
5. Which condition is most likely to cause a trap to lose its water seal
because of negative pressure?
A. Backpressure
B. Backsiphonage
,C. Siphonage
D. Thermal expansion
Answer: C. Siphonage
Rationale: Siphonage can draw water out of a trap when negative
pressure develops in the drainage or vent system. Proper venting helps
protect trap seals.
6. What is the purpose of a plumbing vent system?
A. Increase water pressure
B. Supply drinking water
C. Protect trap seals and allow drainage-system air movement
D. Heat drainage water
Answer: C. Protect trap seals and allow drainage-system air
movement
Rationale: Venting balances pressures within the drainage system and
helps prevent trap siphonage or excessive positive pressure.
7. Which material is commonly used for potable-water distribution
piping?
A. Cast iron soil pipe
B. Copper tubing
C. Clay sewer pipe
D. Concrete pipe
Answer: B. Copper tubing
Rationale: Copper tubing is widely used for potable-water distribution
because it is durable, corrosion resistant in many applications, and
suitable for pressurized water systems.
8. What is the main purpose of a pressure-reducing valve?
, A. Increase supply pressure
B. Reduce excessive incoming water pressure
C. Remove sewer gases
D. Increase drainage slope
Answer: B. Reduce excessive incoming water pressure
Rationale: A pressure-reducing valve controls excessive supply
pressure to protect fixtures, piping, valves, and appliances.
9. What does water hammer describe?
A. A sewer stoppage
B. A pressure surge caused by rapid fluid movement changes
C. A leaking water heater
D. A failed trap primer
Answer: B. A pressure surge caused by rapid fluid movement
changes
Rationale: Water hammer occurs when moving water is stopped or
redirected rapidly, producing a pressure wave that can create noise,
vibration, and damage.
10. Which device can help control thermal expansion in a closed
potable-water system?
A. Expansion tank
B. Cleanout
C. Trap
D. Vent stack
Answer: A. Expansion tank
Examination Questions And Correct
Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
1. Which component prevents contaminated water from flowing
backward into a potable water supply?
A. Cleanout
B. Trap primer
C. Backflow prevention device
D. Expansion tank
Answer: C. Backflow prevention device
Rationale: A backflow prevention device is specifically designed to
protect potable water from contamination caused by backpressure or
backsiphonage.
2. What is the primary purpose of a plumbing trap?
A. Increase water pressure
B. Prevent sewer gases from entering a building
C. Increase drainage velocity
D. Reduce water temperature
Answer: B. Prevent sewer gases from entering a building
,Rationale: A properly installed trap maintains a water seal that
prevents gases from the drainage system from entering occupied
spaces.
3. Which fitting is normally used to change the direction of a
drainage pipe while maintaining proper flow?
A. Sanitary tee
B. Drainage elbow
C. Coupling
D. Union
Answer: B. Drainage elbow
Rationale: Drainage-pattern elbows provide a smoother transition and
are intended to direct waste flow without creating unnecessary
turbulence.
4. What is the principal purpose of a cleanout?
A. Measure water pressure
B. Provide access for cleaning a drainage system
C. Prevent thermal expansion
D. Control fixture temperature
Answer: B. Provide access for cleaning a drainage system
Rationale: A cleanout provides an accessible opening through which
approved equipment can be inserted to clear obstructions from
drainage piping.
5. Which condition is most likely to cause a trap to lose its water seal
because of negative pressure?
A. Backpressure
B. Backsiphonage
,C. Siphonage
D. Thermal expansion
Answer: C. Siphonage
Rationale: Siphonage can draw water out of a trap when negative
pressure develops in the drainage or vent system. Proper venting helps
protect trap seals.
6. What is the purpose of a plumbing vent system?
A. Increase water pressure
B. Supply drinking water
C. Protect trap seals and allow drainage-system air movement
D. Heat drainage water
Answer: C. Protect trap seals and allow drainage-system air
movement
Rationale: Venting balances pressures within the drainage system and
helps prevent trap siphonage or excessive positive pressure.
7. Which material is commonly used for potable-water distribution
piping?
A. Cast iron soil pipe
B. Copper tubing
C. Clay sewer pipe
D. Concrete pipe
Answer: B. Copper tubing
Rationale: Copper tubing is widely used for potable-water distribution
because it is durable, corrosion resistant in many applications, and
suitable for pressurized water systems.
8. What is the main purpose of a pressure-reducing valve?
, A. Increase supply pressure
B. Reduce excessive incoming water pressure
C. Remove sewer gases
D. Increase drainage slope
Answer: B. Reduce excessive incoming water pressure
Rationale: A pressure-reducing valve controls excessive supply
pressure to protect fixtures, piping, valves, and appliances.
9. What does water hammer describe?
A. A sewer stoppage
B. A pressure surge caused by rapid fluid movement changes
C. A leaking water heater
D. A failed trap primer
Answer: B. A pressure surge caused by rapid fluid movement
changes
Rationale: Water hammer occurs when moving water is stopped or
redirected rapidly, producing a pressure wave that can create noise,
vibration, and damage.
10. Which device can help control thermal expansion in a closed
potable-water system?
A. Expansion tank
B. Cleanout
C. Trap
D. Vent stack
Answer: A. Expansion tank
