Washington runs plumbing certification at the state level, and the plumbing license Washington requires is issued by the Department of Labor & Industries (L&I). Everyone doing plumbing work needs an L&I credential, from day-one trainees to journey-level plumbers, and if you want your own company there’s a separate plumbing contractor registration on top.
Who’s in charge
The Washington State Department of Labor & Industries handles plumber certification, exams, renewals, and contractor registration. Everything runs through L&I’s site.
Certification levels
- Plumber trainee. Where everyone starts. You register with L&I and work under the supervision of a certified plumber while you bank hours.
- Journey-level plumber. The full credential: qualified for all phases of plumbing work. Requires at least 8,000 hours (roughly four years) as a trainee, of which at least 4,000 hours must be commercial or industrial work, then a 70% pass on the journey-level exam.
- Residential specialty plumber. A narrower certification limited to residential work, with a shorter experience path than journey-level. If you plan to stay in houses, ask L&I whether this track fits before grinding out commercial hours.
Keeping it current
Washington takes continuing education seriously: journey-level and residential specialty plumbers need 24 hours of CE per renewal period, including at least 12 hours of Uniform Plumbing Code instruction and 4 hours of industry-related electrical training.
Running your own plumbing business
Your personal certification lets you do the work. To contract jobs, the business also needs to register as a plumbing contractor with L&I, which means a bond and liability insurance on file. Plan for both layers before you print business cards. The business setup itself, entity, insurance, pricing, first customers, is exactly what our how to start a plumbing business guide covers.
How to apply
- Register as a plumber trainee with L&I and start logging supervised hours.
- Track your hours carefully (L&I requires reported, verifiable experience).
- Apply for the journey-level or residential specialty exam when your hours qualify, and pass with at least 70%.
- If you’re going independent, file the plumbing contractor registration with bond and insurance.
FAQ
Can I do any plumbing work without an L&I credential? No, even trainees must be registered and supervised. Unpermitted, uncertified work risks fines and stop-work orders.
How long does journey-level take? About four years of full-time work (8,000 hours), assuming half of it is commercial or industrial.
Does Washington recognize out-of-state experience? L&I evaluates documented out-of-state hours case by case, submit your records and ask before assuming you’ll retest from zero.
What does it compare to? Washington’s hour requirements sit on the higher end. See California for a state that routes contracting through a contractor board instead.
Requirements change. Always confirm current rules, hours, and fees with L&I before you apply. General information, not legal advice.
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