Washington State Plumbing License Requirements: Complete Guide (2024-2026)
Washington State Plumbing License Requirements: Complete Guide (2024-2026)
Last updated: March 2025 | Based on RCW 18.106 and WAC 296-400A
Washington State requires plumbers to hold valid certifications to protect public health and safety. From trainees to journey-level plumbers, and specialists like medical gas installers and backflow assembly testers, this guide covers all plumbing certification requirements in Washington.
Overview: Washington Plumbing Certification Structure
The Department of Labor & Industries (L&I) administers plumbing certifications under the Plumbers Law (RCW 18.106).
| Credential Type | Who Needs It | Pathway |
|---|---|---|
| Plumber Trainee | Anyone learning plumbing | Enrollment, no exam |
| Journeyman Plumber | Full plumbing work authority | 8,000 hours + exam |
| Specialty Plumber | Limited scope work | 4,000 hours + specialty exam |
| Backflow Assembly Tester (BAT) | Cross-connection testing | Training + exam |
| Medical Gas Piping Installer | Medical facility gas systems | Journey + specialized training |
⚠️ Important: Plumbing contractors also need general contractor registration under RCW 18.27, with appropriate bonding and insurance.
Journeyman Plumber Certification
The Full Journey-Level Path
The Journeyman Plumber certification is the primary credential for performing all types of plumbing work in Washington.
Requirements (WAC 296-400A-025):
| Requirement | Details |
|---|---|
| Work Experience | 8,000 hours (approximately 4 years) |
| Training | State-approved curriculum or apprenticeship |
| Supervision | Under certified plumber at 1:2 ratio |
| Age | 18 years minimum at certification |
| Exam | Written examination, 75% passing score |
| Exam Fee | $76.50 |
| Certificate Fee | $76.50 |
Scope of Work:
- All plumbing installations in residential, commercial, and industrial settings
- Water supply and distribution systems
- Drainage, waste, and vent (DWV) systems
- Gas piping systems
- Plumbing fixtures and appliances
- Water heater installation
Experience Requirements in Detail
| Experience Category | Hours Credited |
|---|---|
| Direct plumbing work | 100% of hours |
| Related construction | Up to 50% credit |
| Military plumbing | 100% of verified hours |
| Out-of-state (licensed) | 100% with verification |
| Out-of-state (unlicensed) | Case-by-case review |
Specialty Plumber Certifications
Washington offers several specialty certificates for limited plumbing scopes:
Residential Plumber (02)
| Requirement | Details |
|---|---|
| Experience | 4,000 hours residential plumbing |
| Exam | Residential plumbing exam |
| Scope | Single-family and multi-family residential only |
| Limitations | Cannot work on commercial/industrial |
Maintenance Specialty (MS)
| Requirement | Details |
|---|---|
| Experience | 4,000 hours in maintenance setting |
| Employer | Industrial or institutional facility |
| Scope | Maintenance at single employer location |
| Limitations | Not valid for new construction |
Medical Gas Piping Installer (MGPI)
| Requirement | Details |
|---|---|
| Prerequisites | Journey-level plumber certification |
| Training | ASSE 6010 or equivalent program |
| Brazing Certification | Required for medical gas work |
| Scope | Medical gas systems in healthcare facilities |
Backflow Assembly Tester (BAT) Certification
Purpose
Backflow Assembly Testers inspect and test backflow prevention devices that protect public water supplies from contamination.
Requirements (WAC 246-292-020)
| Requirement | Details |
|---|---|
| Administering Agency | Washington State Dept. of Health |
| Training Course | 40-hour approved course |
| Exam | Written + practical demonstration |
| Passing Score | 80% minimum |
| Certification Fee | $103 |
| Renewal | Every 3 years |
| Continuing Education | 8 hours per renewal cycle |
Who Needs BAT Certification
- Plumbers testing backflow devices
- Water utility employees
- Maintenance personnel responsible for backflow testing
- Third-party testers
Note: BAT certification is separate from plumber certification. A plumber can install backflow devices, but testing requires BAT certification.
Course Providers
Approved courses are offered by:
- Community and technical colleges
- Water utility training programs
- Private training providers approved by Dept. of Health
Plumber Trainee Program
Getting Started
Anyone can begin training as a plumber in Washington:
Step 1: Apply for Trainee Certificate
- Submit application to L&I
- Fee: $52.70
- No prior experience required
- Must be at least 16 years old
Step 2: Find Employment
- Must work for licensed plumbing contractor
- Work under certified plumber supervision
- Maximum ratio: 2 trainees per 1 certified plumber
Step 3: Track Hours
- Maintain work hour log
- Document types of plumbing work
- Verify hours with certified supervisor signatures
Supervision Requirements (WAC 296-400A-060)
| Setting | Supervision Ratio |
|---|---|
| New construction | 1 certified : 2 trainees maximum |
| Service/repair | Direct supervision (same job site) |
| Underground work | 1 certified : 1 trainee (first 2,000 hours) |
Direct Supervision Defined:
- Certified plumber on same job site
- Available for immediate consultation
- Can observe and direct trainee's work
- Responsible for quality and code compliance
Violations and Penalties
| Violation | Penalty |
|---|---|
| Trainee working unsupervised | Up to $5,000 fine |
| Exceeding supervision ratio | Up to $5,000 fine |
| Falsifying work hours | Certificate denial/revocation |
Plumbing Contractor Requirements
Operating a Plumbing Business
To operate a plumbing contracting business, you need:
| Requirement | Details |
|---|---|
| L&I Contractor Registration | Active registration under RCW 18.27 |
| Surety Bond | $15,000 (specialty) or $30,000 (general) |
| Liability Insurance | $200,000 minimum |
| Certified Plumber on Staff | Journey-level or specialty |
| Business License | State and local as required |
Who Must Be Certified
| Role | Certification Required |
|---|---|
| Business owner doing plumbing work | Yes |
| Employees doing plumbing work | Yes (journey or trainee) |
| Business owner supervising only | No (but must employ certified plumbers) |
| Office/administrative staff | No |
Examination Details
Journey-Level Plumber Exam
| Detail | Information |
|---|---|
| Format | Computer-based, multiple choice |
| Questions | 100 questions |
| Time Limit | 4 hours |
| Passing Score | 75% (75 correct) |
| Reference Allowed | Current Uniform Plumbing Code |
| Locations | L&I-approved testing centers |
| Cost | $76.50 |
Exam Topics
- General Knowledge — 10%
- Water Supply Systems — 25%
- DWV Systems — 30%
- Fixtures and Appliances — 15%
- Gas Piping — 10%
- Calculations — 10%
Tips for Passing
- Study the Uniform Plumbing Code (current edition)
- Focus on drainage fixture unit calculations
- Know water pipe sizing methods
- Practice with sample exams
- Attend a prep course if available
Fees and Timelines (2024-2025)
Certification Fees
| Item | Fee |
|---|---|
| Trainee certificate | $52.70 |
| Journey-level exam | $76.50 |
| Journey-level certificate | $76.50 |
| Specialty exam | $76.50 |
| Specialty certificate | $76.50 |
| Certificate renewal (3-year) | $76.50 |
| Backflow tester (DOH) | $103.00 |
| Late renewal penalty | 50% of fee |
Processing Timeline
| Application Type | Timeline |
|---|---|
| Trainee certificate | 1-2 weeks |
| Exam approval | 2-3 weeks after application |
| Certificate after passing exam | 2-4 weeks |
| Renewal | 1-2 weeks |
Continuing Education
| Certificate Type | CE Hours Required |
|---|---|
| Journey-level | 8 hours per 3-year cycle |
| Specialty | 8 hours per 3-year cycle |
| Backflow Tester | 8 hours per 3-year cycle |
Exemptions from Plumbing Certification
Under RCW 18.106.010, these activities are exempt:
Work Not Requiring Certification
- Homeowner work — On owner-occupied single-family residence (permit still required)
- Appliance replacement — Like-for-like water heater replacement by homeowner
- Fixture replacement — Faucets, toilets, garbage disposals (no pipe modification)
- Landscaping irrigation — Non-potable irrigation systems
- Utility employees — Working for water/sewer utilities
Homeowner Exception Details
Homeowners can perform plumbing work on their owner-occupied residence if:
- They personally perform the work (no hired help)
- They obtain required permits
- Work passes inspection
- Not rental property or for-sale property
⚠️ Warning: The homeowner exception does not apply to gas piping work. Gas line installation requires certification regardless of who owns the property.
Reciprocity with Other States
Out-of-State Plumbers
Washington does not have automatic reciprocity. However:
| Situation | Process |
|---|---|
| Licensed in another state | Apply for exam; full hours may be credited |
| ICC certification | Not accepted alone; must take WA exam |
| Military training | Hours credited with documentation |
Getting Washington Certification
Out-of-state plumbers must:
- Submit verification of out-of-state license
- Provide work hour documentation
- Apply for examination
- Pass Washington plumber exam
Penalties for Unlicensed Plumbing
Criminal Penalties (RCW 18.106.020)
| Violation | Classification |
|---|---|
| Working without certification | Gross misdemeanor |
| Employing uncertified plumbers | Gross misdemeanor |
| Falsifying certification | Class C felony |
Civil Penalties
| Violation | Fine |
|---|---|
| First violation | $200 - $5,000 |
| Repeat violation | Up to $10,000 |
| Each day of violation | Separate offense |
Additional Consequences
- Cannot sue for payment in court
- No mechanic's lien rights
- Consumer Protection Act liability
- Insurance may deny claims
- Work may need to be redone by certified plumber
How Homeowners Should Verify
Before Hiring a Plumber
☐ Verify contractor registration at secure.lni.wa.gov/verify ☐ Check plumber certification for individuals who will work on site ☐ Confirm appropriate certification level (journey vs. specialty) ☐ Verify insurance is current ☐ For backflow work, verify BAT certification with Dept. of Health
Questions to Ask
- "What is your L&I contractor registration number?"
- "Are your plumbers journey-level certified?"
- "Will you be pulling the plumbing permit?"
- "Can I see the plumber's certification card?"
- "For backflow testing, do you have BAT certification?"
Red Flags
- Cannot provide certification numbers
- Says they don't need certification for "small repairs"
- Suggests you pull the permit yourself
- Trainees working without certified plumber on site
- Unlisted on L&I verification system
Resources
- Verify Plumber Certifications: secure.lni.wa.gov/verify
- L&I Plumbing Program: 1-800-647-0982
- RCW 18.106 (Plumbers Law): app.leg.wa.gov/rcw/default.aspx?cite=18.106
- WAC 296-400A (Plumbing Rules): apps.leg.wa.gov/wac/default.aspx?cite=296-400A
- Backflow Tester Certification (DOH): doh.wa.gov/licenses-permits-and-certificates/professions-new-renew-702or-update/cross-connection-control-specialist
- Apprenticeship Programs: lni.wa.gov/licensing-permits/apprenticeship
This guide is for informational purposes only and does not constitute legal advice. For specific legal questions, consult a Washington-licensed attorney.