Washington State offers one of the most lucrative and well regulated plumbing markets in the nation. It is also one of the most difficult places to break into the plumbing trade. With plumbers ranking seventh nationally for wages and a projected 10% growth rate through 2033, the Evergreen State provides excellent opportunities for skilled tradespeople. However, Washington also maintains some of the strictest licensing requirements in the country, with mandatory certification at every level and active enforcement throughout all 39 counties.
This comprehensive guide walks you through every step of becoming a licensed plumber in Washington, from trainee to journey-level certification, and explains the mandatory contractor licensing requirements that took effect in 2021.
Read this shorter article on the 5 steps of becoming a plumber.
Understanding Washington’s Plumbing Certification System
Washington’s Department of Labor & Industries (L&I) regulates over 6,000 plumbers, 4,000 plumber trainees, and 600 medical gas installers through its Plumber Certification Program. The system ensures public safety by requiring certification for all plumbing work on someone else’s property, though property owners can perform plumbing work on properties they own.
What constitutes plumbing work requiring certification:
- Potable water building supply and distribution pipes
- Plumbing fixtures and traps
- Drainage and vent pipes
- Accessories within property lines
- Medical gas and medical vacuum systems
- Water heaters
Important exception: Certification is not required for plumbing systems outside buildings (such as municipal water main connections or sewer line connections), except for domestic pump and irrigation systems.
Step 1: Obtain Your Plumber Trainee Certificate
Every plumbing professional in Washington must begin as a certified trainee. This certificate allows you to work under direct supervision while gaining the experience needed for advanced certification.
Requirements:
- Be at least 16 years old
- Submit application with $56.40 fee
- Complete 8 hours of continuing education annually for renewal
Continuing education breakdown for trainees: Over each two-year period, you must complete:
- Minimum 8 hours of plumbing code classes
- Minimum 4 hours of electrical trade-related classes
- 4 hours of additional plumbing or electrical courses
You must complete at least 8 hours annually to maintain an active certificate. For example, if you take 8 hours of code classes one year, the following year you must take at least 4 hours of electrical plus 4 hours in any approved category.
Critical note: You must maintain an active trainee certificate to receive credit for work experience hours. Letting your certificate lapse means any work during that period won’t count toward your licensing requirements.
Step 2: Complete Required Training and Experience
Washington requires substantial supervised experience before you can test for certification. Most trainees complete this through formal apprenticeship programs, though you can also work directly for licensed plumbing contractors.
Experience Requirements by License Type
Journey Level Plumber (PL01):
- 8,000 hours minimum (approximately 4 years)
- At least 4,000 hours must be in commercial or industrial work
- Qualified to work in all phases of plumbing construction
Residential Plumber (PL02):
- 6,000 hours minimum (approximately 3 years)
- Limited to single-family dwellings, duplexes, and apartment buildings up to 3 stories
Residential Service Plumber (PL04):
- 4,000 hours minimum (approximately 2 years)
- First 2,000 hours must be under journey-level or residential specialty plumber supervision
- In single-family dwellings and duplexes: can service, repair, or replace existing fixtures outside interior walls or above floor level
- In any residential structure: can perform drain cleaning and leak repairs from the leak to the next serviceable connection
Pump and Irrigation Plumber (PL03):
- 4,000 hours minimum (approximately 2 years)
- Requires electrical certification
- Limited to equipment for acquiring, treating, storing, or moving drinking or irrigation water
Domestic Well Plumber (PL03A):
- 2,000 hours minimum (approximately 1 year)
- Requires electrical certification
- Limited to pumps not exceeding 100 gallons per minute or 7.5 horsepower, single phase
Backflow Plumber (PL30):
- Requires active Backflow Assembly Tester (BAT) certification from Washington State Department of Health
- Limited to maintenance and repair of existing backflow prevention assemblies
- Does not include installing or replacing assemblies
Apprenticeship Programs
Washington mandates that employers follow an apprentice model, pairing new employees with licensed plumbers for hands-on training. Formal apprenticeship programs are available through:
- Union programs: United Association Local 26 (Seattle), Local 32 (Renton), Local 44 (Spokane), Local 598 (Pasco)
- Technical colleges: Renton Technical College, Bates Technical College, Clover Park Technical College, Perry Technical Institute, South Puget Sound Community College
Apprenticeship requirements:
- Be at least 18 years old
- High school diploma or GED
- Valid Washington driver’s license
- Pass drug screening and background checks
- Complete high school algebra with “C” or better, or pass aptitude test
Important restriction: Hours of experience from out-of-state employers and apprenticeship programs are not eligible for Washington certification. However, out-of-state plumbers can apply for credential review and temporary permits.
Step 3: Pass the Plumbing Certification Exam
Once you’ve completed the required hours and continuing education, you can apply to take the state certification exam.
Exam Application Process
Application requirements:
- Submit affidavits of experience documenting your hours
- Complete continuing education requirements
- Pay non-refundable application fee of $189.80
- Applications processed first-come, first-served
- Approved applications valid for one year
Important note: Out-of-state experience hours are not eligible for Washington certification. Out-of-state plumbers must go through a separate credential review process.
Exam Details
Exams are administered by PSI Services with 15 testing locations throughout Washington. After L&I approves your application, you’ll receive instructions to contact PSI directly to schedule and pay for your exam.
Exam format varies by license type:
- Journey Level and Residential: Three portions (150 total questions)
- Specialty licenses: Single portion (45-85 questions depending on specialty)
- Time limit: 90 minutes per portion
- Passing score: 70%
- PSI scheduling fee: Separate fee paid directly to PSI (amount varies)
Critical scheduling rules:
- Must contact PSI at least 2 days before your scheduled date to reschedule
- Phone call required – voicemails and emails not accepted
- Missing your appointment or failing to reschedule properly results in forfeiting your scheduling fee
Re-testing Requirements
If you fail the exam:
- Submit new application with $189.80 fee
- Wait 14 calendar days before rescheduling
- Process essentially starts over
Step 4: Pay Certification Fees and Receive License
After passing your exam, you have 90 days to pay the certification fee:
- Journey Level/Residential/Residential Service: $227.90
- Medical Gas Endorsement: $156.70
- Domestic Pump/Pump and Irrigation: $228.00
- Backflow Specialty: $157.20
Step 5: Understand Mandatory Contractor Licensing (Critical 2021 Change)
As of July 1, 2021, you must be employed by a licensed plumbing contractor to perform any contract plumbing work in Washington. This requirement fundamentally changed the industry structure and affects all certified plumbers.
What Changed
The 2020 Legislature (Senate Bill 6170) eliminated the previous “specialty plumbing” registration and created mandatory plumbing contractor licensing. Key changes:
- All plumbing contract work must be performed by licensed plumbing contractors
- General contractors can no longer perform plumbing work with just a certified plumber on staff
- Only licensed plumbing contractors can employ certified plumbers for plumbing jobs
- Licensed plumbing contractors are the only entities that can advertise, bid on, or perform contract plumbing work
Plumbing Contractor Requirements
To become a licensed plumbing contractor:
Business registration:
- Register with Department of Revenue
- Corporations, LLCs, and partnerships must also file with Secretary of State
- Obtain Employee Identification Number (unless sole proprietor with no employees)
Financial requirements:
- Surety bond or assigned savings account: $6,000
- General liability insurance: $250,000 combined single limit OR $200,000 public liability + $50,000 property damage
- L&I must be listed as certificate holder on insurance
Application process:
- Complete notarized Application for Plumbing Contractor License
- Complete Designated Plumber Assignment form
- Pay application fee: $139.10
- Pay designated plumber fee: $50.00
Designated plumber requirement: Every plumbing contractor must assign a certified plumber as their “designated plumber.” This can be an owner, partner, or full-time employee with appropriate certification.
Processing and Renewal
Processing time: 1-2 weeks by mail after receipt Renewal: Every year with $139.10 fee License verification: All active contractors listed in L&I’s online verification tool
Suspension and Reinstatement
L&I suspends licenses when requirements aren’t met (bond/insurance cancellation, unsatisfied judgments). Suspension notification comes within 2 days by certified and first-class mail.
Reinstatement requirements:
- Correct the underlying issue
- Pay $69.50 reinstatement fee
- Can reinstate online (immediate activation), in person, or by mail
Step 6: Maintain Your Certification
Continuing Education Requirements
Requirements vary significantly by license type and changed effective July 1, 2021:
Journey Level and Residential Specialty Plumbers:
- 24 hours per renewal period
- Minimum 12 hours Uniform Plumbing Code
- Minimum 4 hours Industry-Related Electrical
- Remaining 8 hours in any Code, electrical, or plumbing area
Pump and Irrigation/Domestic Pump Plumbers:
- 24 hours plumbing continuing education
- Plus 24 hours electrical continuing education (48 total)
- Can take combination classes counting toward both programs
- Electrical program accepts up to 12 hours of plumbing courses
Backflow Specialty Plumbers:
- No continuing education required
- Must submit copy of active BAT card for renewal
Medical Gas Piping Installers:
- Submit notarized affidavits of brazing experience every 6 months
Renewal Schedule
- Journey Level, Residential, Residential Service: Every 3 years on your birthday
- Specialty licenses: Varies by type
- Plumbing Contractors: Annually
Important Deadlines
Consequences of late renewal:
- Certificate becomes inactive if continuing education not completed by renewal date
- Late fees apply
- Must retest if continuing education and fees not completed within 90 days of renewal
Salary Expectations in Washington
Washington offers some of the highest plumbing wages in the nation, with the state ranking seventh nationally for plumber compensation.
Current wage data:
- Annual mean wage: $82,400 (vs. $67,840 national average)
- Apprentice: $23.89/hour plus $5,500 average overtime annually
- Journeyman: $41.21/hour plus $6,750 average overtime annually
- Union rates (Local 26): Approximately $65/hour
Additional sources report:
- Average $78,968-$79,993 annually
- Top earners over $100,000-$130,000 annually
- 20% wage premium for union members
Wages vary significantly by region, with Seattle metro area typically offering higher compensation than rural areas.
Special Considerations
Out-of-State Plumbers
Reciprocity: Washington has reciprocal certification with Idaho for journey-level plumbers only.
Other states: Must undergo credential review and pass Washington exam. U.S. military members can show equivalent experience for consideration.
Temporary permits: Out-of-state plumbers with current licenses can apply for one-time 120-day temporary permits ($94.20 fee) while waiting to take the Washington exam. Not available if you’ve previously held Washington certification.
Medical Gas Specialization
Journey-level plumbers can add medical gas piping installer (MG01) endorsement by completing 32 hours of L&I-approved medical gas training and passing the endorsement exam.
Upcoming Changes
L&I is implementing electronic insurance submission systems (expected January 2026) and considering fee increases. The plumbing contractor licensing system continues evolving through ongoing rulemaking as the 2021 changes are fully implemented.
Resources and Contact Information
L&I Plumber Certification Program:
- Email: plumbers@lni.wa.gov
- Phone: 360-902-5207
- Mail: PO Box 44470, Olympia WA 98504-4470
Apprenticeship information: Washington State Apprentice and Training Council (WSATC)
Legal framework:
- Washington Administrative Code Chapter 296-400A
- Revised Code of Washington Chapter 18.106
Compliance reporting: Contact local L&I office or call fraud hotline at 1-888-811-5974
Summary
Becoming a plumber in Washington requires significant commitment but offers substantial rewards. The process typically takes 2-4 years depending on your chosen specialty, involves rigorous training and examination requirements, and now mandates working within the licensed contractor framework established in 2021.
Key takeaways:
- Start as certified trainee (minimum age 16)
- Complete 2,000-8,000 hours supervised experience depending on specialty
- Pass state certification exam
- Must work for licensed plumbing contractor to perform contract work
- Maintain certification through continuing education and timely renewal
- Washington offers among the highest plumbing wages nationally with strong job growth projections
The investment in time and training pays off with excellent wages, job security, and opportunities for advancement in one of the nation’s most professional and well-regulated plumbing markets.