100+ Free WA Plumber Practice Questions

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Question 1

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Which agency oversees plumber licensing in Washington State?

Washington Department of Commerce

Washington Department of Labor & Industries (L&I)

Washington State Department of Health

Washington Department of Licensing

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Free Journeyman Plumber Practice Test by State 2026: 4,700+ Questions24 min read

2026 Statistics

Key Facts: WA Plumber Exam

70%

Passing Score

WA L&I

~100

Exam Questions

PSI exam format

3 hrs

Time Limit

PSI

UPC 2015

Code Base

Washington adoption

The Washington journeyman plumber exam is administered through PSI and overseen by L&I. The exam has approximately 100 questions with a 3-hour time limit, requiring 70% to pass. Washington uses the UPC 2015 with state amendments — a key distinction from IPC states. The UPC requires a 4-inch minimum building sewer and does not permit AAVs.

Sample WA Plumber Practice Questions

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

1Which agency oversees plumber licensing in Washington State?

A.Washington Department of Commerce

B.Washington Department of Labor & Industries (L&I)

C.Washington State Department of Health

D.Washington Department of Licensing

Explanation: The Washington Department of Labor & Industries (L&I) oversees plumber licensing in the state. L&I administers the plumbing program, issues licenses, and enforces the state plumbing code.

2Washington State's plumbing code is based on which model code?

A.International Plumbing Code (IPC)

B.National Standard Plumbing Code (NSPC)

C.Uniform Plumbing Code (UPC) 2015 with Washington amendments

D.Uniform Plumbing Code (UPC) 2024

Explanation: Washington State uses the Uniform Plumbing Code (UPC) 2015 edition with Washington State amendments as the basis for its plumbing regulations. The UPC is published by IAPMO and adopted by many western states.

3What is the passing score required on the Washington journeyman plumber exam?

A.60%

B.65%

C.70%

D.75%

Explanation: Washington requires a 70% passing score on the journeyman plumber exam administered through PSI. The exam consists of approximately 100 multiple-choice questions with a 3-hour time limit.

4Per the UPC, 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 the UPC, horizontal drainage pipes 3 inches and larger require a minimum slope of 1/8 inch per foot (approximately 1% grade). This ensures adequate flow velocity for waste transport while maintaining reasonable vertical drops.

5Per the UPC, what is the DFU (Drainage Fixture Unit) value for a water closet (flush tank type)?

A.2 DFU

B.3 DFU

C.4 DFU

D.6 DFU

Explanation: Per the UPC, a water closet with a flush tank (gravity tank) has a DFU value of 4. This is the same value used for sizing drainage and vent piping. Flush valve (flushometer) water closets may have different DFU values.

6Per the UPC, what is the minimum building sewer size?

A.3 inches

B.4 inches

C.6 inches

D.Depends on DFU load only

Explanation: Per the UPC, the minimum building sewer size is 4 inches. This differs from the IPC which allows 3-inch building sewers. The UPC 4-inch minimum provides greater capacity and reduces the risk of blockages.

7Per the UPC, what is the maximum distance between cleanouts in a horizontal drainage line?

A.50 feet

B.75 feet

C.100 feet

D.150 feet

Explanation: Per the UPC, cleanouts must be installed at intervals not exceeding 100 feet in horizontal drainage lines. Additional cleanouts are required at each aggregate change of direction exceeding 135 degrees.

8Per the UPC, what is the minimum trap seal depth?

A.1 inch

B.2 inches

C.3 inches

D.4 inches

Explanation: The UPC requires a minimum trap seal depth of 2 inches for most fixtures. The maximum trap seal is 4 inches. The water seal in the trap prevents sewer gases from entering the building.

9Per the UPC, what is the maximum number of fixture units allowed on a 2-inch horizontal branch?

A.3 DFU

B.6 DFU

C.12 DFU

D.16 DFU

Explanation: Per the UPC fixture unit tables, a 2-inch horizontal branch drain can serve a maximum of 6 DFUs. This limit ensures the pipe has adequate capacity for the fixtures connected to it.

10Per the UPC, what type of fitting is required for a horizontal change of direction in a drainage system?

A.Any standard elbow

B.Long-sweep fittings or combination of fittings with equivalent sweep

C.Short-radius elbows

D.Sanitary tee only

Explanation: The UPC requires long-sweep fittings or a combination of fittings with an equivalent sweep for horizontal changes of direction in drainage systems. Long-sweep fittings maintain proper flow patterns and reduce the risk of blockages.

About the WA Plumber Exam

Washington journeyman plumber licensing exam administered by PSI and overseen by L&I. Based on the Uniform Plumbing Code (UPC) 2015 with Washington State amendments. Washington is one of the western states that uses the UPC rather than the IPC, which affects building sewer minimums, AAV usage, and other provisions.

Questions

100 scored questions

Time Limit

3 hours

Passing Score

70%

Exam Fee

$189.80 (exam) + $227.90 (license) (Washington Department of Labor & Industries (L&I))

WA Plumber Exam Content Outline

25%

Drainage Systems

Drain pipe sizing, fixture units (DFU), slope requirements, cleanouts, 4-inch minimum building sewer, indirect waste, and special drainage per UPC 2015 with WA amendments

20%

Water Supply Systems

Water pipe sizing, WSFU calculations, backflow prevention (RPZ/DCVA/AVB), pressure regulation, water heaters, and cross-connection control

20%

Venting Systems

Vent sizing (half-drain rule), wet venting, circuit venting, vent termination, frost closure prevention, and trap seal protection — no AAVs under UPC

15%

Fixtures & Appliances

Fixture installation, clearances (24-inch front clearance per UPC), accessible fixtures, commercial fixtures, and scald prevention

10%

Gas Piping

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

10%

Code Administration & Materials

L&I licensing, permits, inspections, approved materials, joint methods, UPC vs IPC differences, and Washington-specific amendments

How to Pass the WA Plumber Exam

What You Need to Know

Passing score: 70%
Exam length: 100 questions
Time limit: 3 hours
Exam fee: $189.80 (exam) + $227.90 (license)

Keys to Passing

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

WA Plumber Study Tips from Top Performers

1Study the UPC 2015, NOT the IPC — Washington uses the UPC with state amendments

2Know UPC-specific rules: 4-inch minimum building sewer, no AAVs, half-drain vent sizing rule

3Master DFU calculations and drain pipe sizing using UPC fixture unit tables

4Learn the 24-inch front clearance requirement for water closets (different from IPC's 21 inches)

5Practice vent sizing — the UPC requires vents to be at least half the drain diameter

6Study frost closure prevention requirements for vent pipes in Washington's climate

7Review backflow prevention device selection and Washington's cross-connection program

8Study Washington-specific amendments to the UPC that may appear on the exam

Frequently Asked Questions

How hard is the Washington journeyman plumber exam?

The Washington exam is challenging with an estimated 50-60% pass rate. It has approximately 100 questions based on the UPC 2015 with WA amendments and requires 70% to pass. The UPC has different provisions than the IPC used by many other states.

What plumbing code does Washington use?

Washington uses the Uniform Plumbing Code (UPC) 2015 edition with Washington State amendments. The UPC is published by IAPMO and differs from the IPC in areas like building sewer minimums (4 inches vs 3 inches) and AAV usage (not permitted under UPC).

How much does the Washington plumber exam and license cost?

The total cost is approximately $417.70: $189.80 for the PSI exam fee plus $227.90 for the L&I license fee. Check with L&I for current fee schedules.

What key differences exist between the UPC and IPC?

Key UPC differences: 4-inch minimum building sewer (vs 3-inch IPC), no air admittance valves (AAVs), 24-inch front clearance for water closets (vs 21-inch IPC), and the half-drain-diameter vent sizing rule.