Yes, Washington licenses plumbers at the state level, but it calls the license a “certificate of competency.” A plumbing license in Washington comes from the Department of Labor & Industries (L&I), and it’s good statewide. Most people start as a registered trainee, log supervised hours, then pass a PSI exam for a journey level, residential, or other specialty certificate. Plumbing businesses need a separate plumbing contractor license.
Who issues the license
The L&I Plumber Certification Program issues trainee and plumber certificates, approves exam applications, tracks your hours and CE, and licenses plumbing contractors. PSI Services runs the exams for L&I.
The rules come from Chapter 18.106 RCW (Plumbers) and Chapter 296-400A WAC. So when you see “certificate” on L&I forms, read it as “license.” Same thing for our purposes.
Requirements change, so confirm with L&I before you apply. This page is a plain-English guide, not legal advice.
License types
L&I lists these plumber classifications:
- Plumber Trainee. The starting card. You must be 16 or older and work under the direct supervision of a certified plumber. It’s good for 12 months.
- Journey Level (PL01). The full certificate. You can do all types of plumbing, commercial and residential.
- Residential Specialty (PL02). Plumbing in single-family homes, duplexes, and apartment buildings of three stories or fewer.
- Residential Service (PL04). A newer certificate limited to service plumbing in existing residential buildings.
- Pump and Irrigation (PL03) and Domestic Well (PL03A). Specialty certificates for the pressurization, treatment, and filtration parts of certain domestic water pumping systems. Trainees in this trade also need an electrical trainee card.
- Backflow Assembly Tester (PL30). A specialty for maintaining and repairing backflow prevention assemblies.
- Medical Gas Endorsement (MG01). An add-on to a journey level certificate. You need it to install medical gas piping.
- Licensed Plumbing Contractor. For the business, not a person. All plumbing contract work has to be done by a licensed plumbing contractor.
Washington has no “master plumber” level. Journey level is the top individual certificate.
How to become a plumber in Washington
Here’s the path under the law and L&I’s rules:
- Get your trainee certificate. Apply to L&I and pay the $60.00 fee. Your hours don’t count unless your trainee card is current.
- Work under supervision and log your hours. At least once a year, each employer or supervising plumber fills out a notarized Plumber’s Affidavit of Experience. Originals only. L&I won’t take copies, faxes, emails, or altered forms, and your own training log doesn’t count.
- Hit the hours for the certificate you want. Under WAC 296-400A-121:
- Journey level: 8,000 hours over at least 4 years, with at least 4,000 hours of commercial plumbing under a journey level plumber.
- Residential specialty: 6,000 hours over at least 3 years.
- Residential service: 4,000 hours over at least 2 years.
- Domestic pump: 2,000 hours over 1 year for limited volume, or 4,000 hours over 2 years for unrestricted.
- Keep up trainee CE. Trainees need 8 hours of approved CE each year to renew.
- Apply for the exam and pass it. L&I reviews your hours and mails you an exam notice if you’re approved.
A few things trip people up. Hours don’t count if you weren’t properly supervised, your card was expired, you owe penalties, or the work was for an out-of-state employer. Apprentice and trade school trainees can apply for an endorsement to work without on-site supervision in their last 6 months.
Exams
PSI gives the exams. Per the PSI candidate bulletin for Washington L&I, you need 70% to pass each one:
- Journey level: three closed-book parts, 90 minutes each. Code and trade knowledge (100 questions), waste and vent drawings (25), and water sizing drawings (25).
- Residential specialty: the same three-part setup, on residential code and drawings.
- Residential service: 65 questions, closed book.
- Backflow: 55 questions, closed book.
- Domestic pump or irrigation: 45 questions, open book.
- Medical gas: 100 questions, open book.
For journey level and residential, you have to pass all three parts. Your eligibility lasts one year. You can retest as often as you want in that year, but you wait 14 days after a failed attempt, and a no-show counts as a fail. Once you pass, you have 90 days to pay the certificate fee or you test again.
Renewal
Plumber certificates renew every 3 years, on your birthday. Your first card runs 25 to 37 months depending on when you apply and your birthdate, and the fee isn’t prorated.
CE before each renewal, per L&I:
- Journey level, residential, and residential service: 24 hours. At least 12 must be plumbing code and at least 4 must be industry-related electrical.
- Pump and irrigation, domestic well: 24 hours, with at least 12 electrical and 12 plumbing.
- Medical gas endorsement: an affidavit of continuity.
- Backflow: a current copy of your backflow tester certification from the Washington Department of Health.
Late? You pay double the fee. If your certificate has been expired 90 days without paying and finishing CE, you have to retest.
Cost
These are the L&I fees in WAC 296-400A-045, effective July 1, 2026:
- Trainee certificate: $60.00 a year.
- Exam application (journey level, residential, residential service, backflow): $202.10 per exam, paid to L&I.
- PSI exam fee: $84 for the three-part exam, or $52 per portion on a retest, paid to PSI.
- Journey level, residential, or residential service certificate: $242.70 for the first card and $242.70 each 3-year renewal.
- Domestic pump certificate: $242.80. Backflow certificate: $167.40.
- Medical gas: $74.30 to apply and $166.90 for the endorsement. The medical gas exam and training course fees go to outside providers and aren’t listed in the rule.
- Reinstatement (journey level and residential): $324.50.
- Plumbing contractor license: $148.10 to issue or renew, plus $53.20 to name your designated plumber.
Heads up: L&I’s contractor page still shows a $139.10 renewal, while the current rule says $148.10. Go with what L&I bills you. Compare states on our plumbing license cost by state page.
Reciprocity
Washington has a reciprocity law, but L&I says it reciprocates with only one state: Idaho.
- Idaho journey level plumbers. Send L&I a copy of your active Idaho journey level card and a government photo ID. The reciprocity application fee is $202.10.
- Everyone else. Send copies of your active out-of-state license and photo ID, or proof of U.S. military experience. L&I reviews it and either asks for the fee or sends a letter saying why it’s denied.
- Temporary permit. If you’re moving in from another state, a 120-day temporary permit ($100.30) can let you work while you wait to test. It’s not issued to apprentices or anyone who has failed the exam.
Oregon isn’t on L&I’s list, so don’t assume your Oregon card transfers. See our plumbing license reciprocity guide for other states.
How to apply
- Online. Use L&I’s online service with your Social Security number and a card or e-check. Your affidavits and documents need to be on file first.
- By mail. Print the Plumber Certification Application (F627-008-000) and send it to L&I Plumber Certification, PO Box 44470, Olympia, WA 98504-4470.
- In person. Go to any L&I field office.
- Starting a business? The plumbing contractor license needs a $6,000 surety bond, general liability insurance, and a designated certified plumber who’s an owner, partner, or full-time employee. It lasts 24 months. If you also do non-plumbing work, you’d also register as a contractor under RCW 18.27, with its own bond ($30,000 general, $15,000 specialty).
Questions? L&I’s plumber line is 360-902-5207, or email Plumbers@Lni.wa.gov.
FAQ
How long does it take to get a plumbing license in Washington?
At least 4 years and 8,000 hours for journey level, 3 years and 6,000 hours for residential, or 2 years and 4,000 hours for residential service.
How much does a Washington plumbing certificate cost?
For journey level, figure $202.10 to L&I and $84 to PSI for the exam, then $242.70 for your card. Add $60.00 a year as a trainee.
Does Washington have a master plumber license?
No. Journey level is the top certificate. To run a business, you get a plumbing contractor license instead.
How much CE do Washington plumbers need?
24 hours every 3 years for journey level and residential, including 12 code and 4 electrical. Trainees need 8 hours a year.
Next steps
Just starting? Get your trainee card first, because hours on an expired card don’t count. Then make sure every employer sends in a notarized affidavit each year. To see how Washington stacks up, check our plumbing license by state page and the full plumbing license guide. Coming from next door? Read the Idaho plumbing license page. Ready to run your own shop? See how to start a plumbing business.
