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Exam Review

Key Facts: CO Plumber Exam

70%

Passing Score

DORA State Plumbing Board

100

Questions

PSI bulletin (updated 11/1/2026): 100 scored items, 240 minutes

$78

Exam Fee

PSI

IPC

Code Basis

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

Colorado's journeyworker plumber exam has 100 scored items in 240 minutes (plus up to 10 unscored items with 30 more minutes) and needs 70 correct to pass. From November 1, 2026 it is based on the 2024 IPC and IRC, which PSI provides at the test center, and it does not test Colorado's state amendments.

Sample CO Plumber Practice Questions

Try these sample questions to review concepts for the CO Plumber exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 436+ 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 journeyworker plumber exam is administered by PSI for the Colorado State Plumbing Board. PSI provides the 2024 IPC and IRC at the test center, and candidates may not mark them or bring other materials. It covers sanitary and storm drainage, vents, water supply, fixtures, water heaters, traps, indirect waste, isometric analysis and residential fire sprinklers, not the state amendments.

Exam sponsor: DORA State Plumbing Board. The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Questions

100 questions

Time Limit

4 hours 30 minutes (240 + 30 minutes)

Passing Score

70%

Exam / Certification Fees

$78 ($73 retest)

Exam sponsor website

Reported exam pass rate: Not published. Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

Official sources

DORA State Plumbing Board: official exam information

Our practice resources: topics covered

We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.

20 of 100 items

Sanitary Drainage Systems