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Under the IPC as adopted in Colorado, what is the minimum size drain pipe required for a water closet?

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Key Facts: CO Plumber Exam

70%

Passing Score

DORA State Plumbing Board

80

Questions

4 hours time limit

$150-$300

Exam Fee

PSI

IPC

Code Basis

Colorado adopts the International Plumbing Code (IPC) with state amendments

Colorado's journeyman plumber exam has approximately a 60% pass rate. The 80-question exam requires 70% to pass and is based on the IPC. Colorado adopts the International Plumbing Code (IPC) with state amendments. The exam is open book..

Sample CO Plumber Practice Questions

Try these sample questions to test your CO Plumber exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Under the IPC as adopted in Colorado, what is the minimum size drain pipe required for a water closet?
A.2 inches
B.3 inches
C.4 inches
D.1-1/2 inches
Explanation: Per IPC drainage pipe sizing tables, the minimum drain size for a water closet is 3 inches. This applies to all types of water closets and ensures adequate capacity to convey solid waste through the drainage system.
2According to the IPC as enforced in Colorado, what is the minimum slope for a 4-inch horizontal drainage pipe?
A.1/16 inch per foot
B.1/8 inch per foot
C.1/4 inch per foot
D.1/2 inch per foot
Explanation: Per IPC slope requirements, horizontal drainage pipes 3 inches and larger must have a minimum slope of 1/8 inch per foot. Pipes smaller than 3 inches require 1/4 inch per foot. Proper slope ensures self-scouring velocity.
3Under Colorado's plumbing code, what is the DFU value for a residential lavatory?
A.1 DFU
B.2 DFU
C.3 DFU
D.0.5 DFU
Explanation: Per IPC fixture unit tables, a residential lavatory is assigned 1 DFU. This value represents the probable discharge rate and is used to size drainage and venting systems.
4Per the IPC as adopted in Colorado, what is the minimum depth of a fixture trap seal?
A.1 inch
B.2 inches
C.3 inches
D.4 inches
Explanation: Per IPC trap requirements, each fixture trap must have a water seal of not less than 2 inches and not more than 4 inches. The 2-inch minimum prevents sewer gases from passing through under normal conditions.
5According to the IPC as enforced in Colorado, at what intervals must cleanouts be installed on horizontal drainage piping 4 inches and smaller?
A.Every 50 feet
B.Every 75 feet
C.Every 100 feet
D.Every 150 feet
Explanation: Per IPC cleanout requirements, cleanouts must be installed at intervals not exceeding 100 feet for pipes 4 inches and smaller. Additional cleanouts are required at each change of direction greater than 45 degrees.
6Under the IPC as adopted in Colorado, what is the maximum number of DFUs that can be connected to a 3-inch horizontal branch?
A.12 DFU
B.20 DFU
C.36 DFU
D.42 DFU
Explanation: Per IPC drain sizing tables, a 3-inch horizontal branch can serve a maximum of approximately 20 DFU. Exceeding this limit risks drainage backup and surcharging.
7Per the IPC as enforced in Colorado, what is the required slope for a 2-inch horizontal drainage pipe?
A.1/16 inch per foot
B.1/8 inch per foot
C.1/4 inch per foot
D.1/2 inch per foot
Explanation: Per IPC slope requirements, pipes smaller than 3 inches require a minimum slope of 1/4 inch per foot. The steeper slope is necessary for smaller pipes to maintain self-scouring velocity.
8According to the IPC as adopted in Colorado, what is the minimum size building sewer when serving more than one water closet?
A.3 inches
B.4 inches
C.6 inches
D.2 inches
Explanation: Per IPC building sewer requirements, a building sewer serving more than one water closet must be at least 4 inches. A single water closet may use a 3-inch sewer in some configurations.
9Under the IPC as enforced in Colorado, what is the maximum tailpiece length from a fixture outlet to the trap weir?
A.12 inches
B.18 inches
C.24 inches
D.36 inches
Explanation: Per IPC trap requirements, the vertical distance from the fixture outlet to the trap weir must not exceed 24 inches. Longer tailpieces risk siphonage and waste buildup.
10Per the IPC as adopted in Colorado, what is the DFU value for a residential bathtub with shower?
A.1 DFU
B.2 DFU
C.3 DFU
D.4 DFU
Explanation: Per IPC fixture unit tables, a residential bathtub with or without a shower is assigned 2 DFU. The shower head does not add fixture units since it shares the same drain and trap.

About the CO Plumber Exam

The Colorado journeyman plumber exam is administered by PSI on behalf of the DORA State Plumbing Board. Colorado plumber exams are open book — candidates may bring approved IPC code books. It tests knowledge of the IPC, drainage systems, water supply, venting, gas piping, and Colorado-specific amendments.

Questions

80 scored questions

Time Limit

4 hours

Passing Score

70%

Exam Fee

$150-$300 (DORA State Plumbing Board)

CO Plumber Exam Content Outline

25%

Drainage, Waste & Vent Systems

IPC drain sizing, fixture units, slope requirements, cleanouts, trap seals, and DWV installation per Colorado amendments

25%

Water Supply & Distribution

Pipe sizing, backflow prevention, cross-connection control, water heaters, pressure regulation, and T&P relief requirements

20%

Venting Systems

Vent sizing, wet venting, circuit venting, air admittance valves, vent termination per the IPC

15%

Gas Piping & Appliances

Gas pipe sizing, BTU calculations, pressure testing, appliance venting, and combustion air requirements

15%

Code Administration & Materials

Permits, inspections, approved materials, joint methods, pipe supports, and Colorado-specific rules

How to Pass the CO Plumber Exam

What You Need to Know

  • Passing score: 70%
  • Exam length: 80 questions
  • Time limit: 4 hours
  • Exam fee: $150-$300

Keys to Passing

  • Complete 500+ practice questions
  • Score 80%+ consistently before scheduling
  • Focus on highest-weighted sections
  • Use our AI tutor for tough concepts

CO Plumber Study Tips from Top Performers

1Master IPC drain sizing tables and fixture unit calculations — heavily tested on the Colorado exam
2Study backflow prevention device selection for different hazard levels per IPC cross-connection requirements
3Memorize minimum pipe sizes, trap sizes, and vent sizes for common residential fixtures
4Practice gas pipe sizing using fuel gas code tables including BTU demand calculations
5Review water heater installation requirements including T&P relief, expansion tanks, and pan requirements

Frequently Asked Questions

What plumbing code does Colorado use?

Colorado adopts the International Plumbing Code (IPC) with state amendments. The exam is open book.. The DORA State Plumbing Board oversees all licensing requirements. The exam is based on the current adopted IPC edition.

How many questions are on the Colorado plumber exam?

The Colorado journeyman plumber exam has approximately 80 multiple-choice questions with a time limit of 4 hours. A score of 70% is required to pass.

Who administers the Colorado plumber exam?

The exam is administered by PSI on behalf of the DORA State Plumbing Board. You must apply through the agency and schedule your exam through PSI's testing system.

What experience is required for the Colorado journeyman plumber exam?

Completion of plumbing apprenticeship (typically 4 years) or equivalent documented experience. Contact the DORA State Plumbing Board for specific requirements and application procedures.