Colorado Journeyman Plumber License
Examination Practice Exam 2026 | 100
Questions & Answers with Detailed
Rationales | Complete Colorado
Journeyman Plumber Exam Prep &
Study Guide
1. What is the primary purpose of a plumbing trap?
A. To increase water pressure
B. To prevent sewer gases from entering a building
C. To increase drainage velocity
D. To filter wastewater
Answer: To prevent sewer gases from entering a building
Rationale: A plumbing trap maintains a water seal that prevents sewer gases
and odors from entering occupied spaces through the drainage system.
2. Which code is identified by Colorado as one of the currently adopted codes
used for plumbing installations?
A. National Electrical Code
B. International Plumbing Code
,C. Uniform Mechanical Code only
D. International Energy Conservation Code only
Answer: International Plumbing Code
Rationale: Colorado identifies the International Plumbing Code (IPC),
International Residential Code (IRC), and International Fuel Gas Code (IFGC)
among the adopted codes used for plumbing installations.
3. What is the primary function of a plumbing vent system?
A. Increase water pressure
B. Carry potable water
C. Protect trap seals and allow proper drainage-system airflow
D. Remove sediment from water
Answer: Protect trap seals and allow proper drainage-system airflow
Rationale: Venting allows air to enter and move through the drainage system,
helping prevent siphonage, backpressure, and loss of trap seals.
4. What condition occurs when wastewater flowing through a drainage pipe
creates negative pressure that can pull water from a trap?
A. Backpressure
B. Back siphonage
C. Self-siphonage
D. Thermal expansion
Answer: Self-siphonage
Rationale: Self-siphonage can occur when a fixture discharges through its own
trap and the resulting flow creates negative pressure capable of removing the
trap seal.
5. What is backpressure in a plumbing system?
,A. Pressure lower than atmospheric pressure
B. Pressure that forces a contaminant or fluid toward the potable-water supply
C. Pressure caused only by water heaters
D. Pressure created by a vent stack
Answer: Pressure that forces a contaminant or fluid toward the potable-water
supply
Rationale: Backpressure is a cross-connection hazard in which the pressure on
the downstream side exceeds the potable-water supply pressure, potentially
reversing flow.
6. What is the purpose of an air gap in a potable-water system?
A. To increase pipe pressure
B. To provide physical separation between the water outlet and a potential source
of contamination
C. To eliminate the need for valves
D. To reduce pipe size
Answer: To provide physical separation between the water outlet and a
potential source of contamination
Rationale: An air gap provides a physical separation that prevents contaminated
water from being drawn or forced into the potable-water system.
7. What is the main purpose of a cleanout?
A. To increase water pressure
B. To provide access for cleaning and clearing drainage piping
C. To regulate hot-water temperature
D. To prevent thermal expansion
Answer: To provide access for cleaning and clearing drainage piping
Rationale: Cleanouts provide accessible openings through which drainage piping
can be inspected, cleaned, or cleared of obstructions.
, 8. Which fixture normally requires a trap?
A. Water closet
B. Hose bibb
C. Water heater
D. Backflow preventer
Answer: Water closet
Rationale: A water closet incorporates an integral trap as part of its fixture
design and does not normally use a separate external trap.
9. What is the primary purpose of a vent stack?
A. Supply potable water
B. Provide ventilation for the drainage system
C. Remove minerals from water
D. Increase fixture pressure
Answer: Provide ventilation for the drainage system
Rationale: A vent stack provides ventilation for drainage piping and helps
protect trap seals from pressure fluctuations.
10. What is the primary function of a sanitary drainage system?
A. Distribute potable water
B. Carry sewage and other permitted liquid wastes to an approved point of
disposal
C. Supply natural gas
D. Collect only rainwater
Answer: Carry sewage and other permitted liquid wastes to an approved point
of disposal
Rationale: Sanitary drainage piping conveys wastewater away from fixtures and
toward an approved disposal or treatment system.
Examination Practice Exam 2026 | 100
Questions & Answers with Detailed
Rationales | Complete Colorado
Journeyman Plumber Exam Prep &
Study Guide
1. What is the primary purpose of a plumbing trap?
A. To increase water pressure
B. To prevent sewer gases from entering a building
C. To increase drainage velocity
D. To filter wastewater
Answer: To prevent sewer gases from entering a building
Rationale: A plumbing trap maintains a water seal that prevents sewer gases
and odors from entering occupied spaces through the drainage system.
2. Which code is identified by Colorado as one of the currently adopted codes
used for plumbing installations?
A. National Electrical Code
B. International Plumbing Code
,C. Uniform Mechanical Code only
D. International Energy Conservation Code only
Answer: International Plumbing Code
Rationale: Colorado identifies the International Plumbing Code (IPC),
International Residential Code (IRC), and International Fuel Gas Code (IFGC)
among the adopted codes used for plumbing installations.
3. What is the primary function of a plumbing vent system?
A. Increase water pressure
B. Carry potable water
C. Protect trap seals and allow proper drainage-system airflow
D. Remove sediment from water
Answer: Protect trap seals and allow proper drainage-system airflow
Rationale: Venting allows air to enter and move through the drainage system,
helping prevent siphonage, backpressure, and loss of trap seals.
4. What condition occurs when wastewater flowing through a drainage pipe
creates negative pressure that can pull water from a trap?
A. Backpressure
B. Back siphonage
C. Self-siphonage
D. Thermal expansion
Answer: Self-siphonage
Rationale: Self-siphonage can occur when a fixture discharges through its own
trap and the resulting flow creates negative pressure capable of removing the
trap seal.
5. What is backpressure in a plumbing system?
,A. Pressure lower than atmospheric pressure
B. Pressure that forces a contaminant or fluid toward the potable-water supply
C. Pressure caused only by water heaters
D. Pressure created by a vent stack
Answer: Pressure that forces a contaminant or fluid toward the potable-water
supply
Rationale: Backpressure is a cross-connection hazard in which the pressure on
the downstream side exceeds the potable-water supply pressure, potentially
reversing flow.
6. What is the purpose of an air gap in a potable-water system?
A. To increase pipe pressure
B. To provide physical separation between the water outlet and a potential source
of contamination
C. To eliminate the need for valves
D. To reduce pipe size
Answer: To provide physical separation between the water outlet and a
potential source of contamination
Rationale: An air gap provides a physical separation that prevents contaminated
water from being drawn or forced into the potable-water system.
7. What is the main purpose of a cleanout?
A. To increase water pressure
B. To provide access for cleaning and clearing drainage piping
C. To regulate hot-water temperature
D. To prevent thermal expansion
Answer: To provide access for cleaning and clearing drainage piping
Rationale: Cleanouts provide accessible openings through which drainage piping
can be inspected, cleaned, or cleared of obstructions.
, 8. Which fixture normally requires a trap?
A. Water closet
B. Hose bibb
C. Water heater
D. Backflow preventer
Answer: Water closet
Rationale: A water closet incorporates an integral trap as part of its fixture
design and does not normally use a separate external trap.
9. What is the primary purpose of a vent stack?
A. Supply potable water
B. Provide ventilation for the drainage system
C. Remove minerals from water
D. Increase fixture pressure
Answer: Provide ventilation for the drainage system
Rationale: A vent stack provides ventilation for drainage piping and helps
protect trap seals from pressure fluctuations.
10. What is the primary function of a sanitary drainage system?
A. Distribute potable water
B. Carry sewage and other permitted liquid wastes to an approved point of
disposal
C. Supply natural gas
D. Collect only rainwater
Answer: Carry sewage and other permitted liquid wastes to an approved point
of disposal
Rationale: Sanitary drainage piping conveys wastewater away from fixtures and
toward an approved disposal or treatment system.
