What license does a plumber need in Washington?
Washington generally requires a state plumber certificate to work in the plumbing trade. However, except for domestic-pump and pump-and-irrigation systems, L&I says certification is not required to install plumbing systems outside a building, including water lines connected directly to municipal mains and sewer-line connections. L&I says certification covers work on potable-water piping, fixtures and traps, drainage and vent piping, medical gas systems, and water heaters. The broad individual credential is Journey Level Plumber, code PL01. Specialty certificates cover narrower scopes.
A PL01 journey-level plumber is qualified to work in all phases of plumbing construction. L&I describes PL01 that way and lists the required experience. If you are comparing Washington with the usual apprentice-to-journey route, start with our general path to a plumbing license.
The business credential is different. Since July 1, 2021, a company that advertises, bids, or performs covered plumbing work generally needs a plumbing contractor license under chapter 18.106 RCW. That change makes the old advice to get an ordinary general or specialty contractor registration incomplete.
PL01 and the Washington plumbing specialties
The right certificate depends on the work you will actually perform:
| Credential | Scope | Minimum documented training |
|---|---|---|
| PL01 Journey Level | All phases of plumbing construction | 8,000 hours over at least four years; 4,000 hours must be commercial plumbing |
| PL02 Residential | Single-family homes, duplexes, and apartment buildings no more than three stories | 6,000 hours over at least three years |
| PL04 Residential Service | Defined service, repair, replacement, drain-cleaning, and leak-repair work in the residential scope | 4,000 hours over at least two years |
| PL03 Pump and Irrigation | Systems used to acquire, treat, store, or move drinking or irrigation water | 4,000 hours over at least two years |
| PL03A Domestic Well | Limited-volume domestic pump systems | 2,000 hours over at least one year |
| PL30 Backflow | Maintenance and repair of existing backflow assemblies inside buildings | Active Washington backflow assembly tester certification |
| MG01 Medical Gas | Medical gas piping work added to a journey-level certificate | At least 32 hours in an L&I-approved medical gas course |
The PL02 residential specialty requires at least 6,000 hours over three years under a certified residential or journey-level plumber. The L&I certification page states both the scope and experience requirement. Pump and domestic-well work also requires electrical certification, so read the Washington electrician licensing rules before choosing that lane.
A specialty can shorten the path, but it also fixes the legal ceiling of your work. Choose PL01 if you expect to move between residential, commercial, and industrial jobs. Choose a specialty only when its limits match the work you plan to sell.
How the trainee path works
For PL01, you may take the examination after completing 8,000 hours and at least four years of documented training, including 4,000 hours of commercial plumbing under direct supervision of a certified journey-level plumber. WAC 296-400A-121 gives that examination threshold.
Use this operating sequence:
- Get a trainee certificate before doing trainee work. The applicant must be at least 16.
- Work within the certificate scope and under the required supervision. Keep an affidavit of experience for every employer and category.
- Renew the trainee certificate every year and submit the prior period hours on time. Hours earned while the card is expired or inactive do not receive credit.
- Complete approved education as you go. Plumber trainees must complete at least eight hours of approved training for each year of the prior certification period. WAC 296-400A-028 also divides the two-year total among plumbing-code, electrical, and elective trade hours.
- Before testing for PL01, PL02, or a domestic-pump specialty, complete 16 hours of continuing education, including at least four hours of industry-related electrical training.
Supervision is not just a signature at the end. Through December 31, 2028, a journey-level plumber working in that capacity may supervise no more than one trainee on a job site, with supervision for at least 75 percent of the time on every job site. WAC 296-400A-120 sets the ratio and on-site percentage. Residential specialty ratios differ and change after that date.
The practical risk is lost credit, not merely a late fee. Renew the card, finish the approved education, and collect signed and notarized affidavits while the employer records are easy to retrieve.
Running a business requires a plumbing contractor license
A PL01 or specialty certificate belongs to the individual. A plumbing contractor license belongs to the business. Since July 1, 2021, covered businesses may not advertise, offer, bid, or perform plumbing work without that contractor license. RCW 18.106.400 states the requirement and provides a narrow owner-residence exemption.
Licensed plumbing contractors under chapter 18.106 RCW are not required to register under the general contractor-registration chapter, chapter 18.27 RCW. That exemption appears in RCW 18.106.400(3). This is the key correction to the older version of this guide: a standard contractor registration is not the business credential for plumbing work.
The contractor must identify a full-time employee or firm member with a valid PL01 or appropriate specialty certificate as the designated certified plumber. WAC 296-400A-011 says that certificate defines the scope the business may perform. A sole owner can fill that role only if the owner holds the right active certificate.
The normal plumbing-contractor security is a $6,000 continuous surety bond or an allowed assigned savings account. RCW 18.106.410 sets the normal bond amount. If the applicant, or a relevant owner, officer, or partner of a current applicant, had a qualifying final judgment involving a residential structure in the prior five years, L&I may require up to three times the normal amount, or $18,000. RCW 18.106.410(11) gives the director that authority.
Separately, the applicant must furnish either insurance or an assigned account as financial responsibility: $50,000 for property damage, $100,000 for injury or death to one person, and $200,000 for injury or death to more than one person. RCW 18.106.420 states those minimum limits. If you use insurance rather than an assigned account, our general liability insurance for contractors guide explains what to inspect beyond the statutory minimum.
The business license lasts no more than two years. The fee schedule effective July 1, 2026 lists $148.10 for issuance, renewal, or reregistration and $53.20 to identify or change the designated plumber. Those amounts appear in WAC 296-400A-045. Bond and insurance premiums, when those products are used, are separate from the state fee; the assigned-account alternatives tie up the required funds instead.
Application, exam, and renewal checklist
For an individual certificate:
- Apply for the trainee certificate and keep it active while earning hours. The current state fee is $60 for one year or an out-of-cycle hours update.
- Document experience by scope and supervisor. PL01 applicants need the four-year and 8,000-hour total, including the commercial component.
- Complete the required approved education.
- Submit the competency-exam application, evidence of experience, education documentation, and the state fee.
- Pass the examination, then pay the first-certificate fee within 90 days of notice that you passed.
To obtain a certificate of competency, an applicant must submit the application, fee, experience evidence, and education documentation, then pass the examination. After passing, the applicant must pay the certification issuance fee within 90 days after notice of passing. WAC 296-400A-020 lists those steps.
Under the fee schedule effective July 1, 2026, the state exam-application fee for PL01, residential, residential-service, or backflow certification is $202.10, and the first PL01, residential, or residential-service card is $242.70. WAC 296-400A-045 notes that a contracted testing provider may charge an additional exam-administration fee.
For the business license, use this state checklist:
- Establish the legal entity, business name, place of business, and active UBI.
- If the applicant will employ workers in Washington, provide the workers’ compensation coverage information, Employment Security Department number, and state excise-tax registration number.
- A UBI may substitute for those three items only when the applicant will not employ workers in Washington. RCW 18.106.400 states that condition.
- Identify the designated certified plumber.
- Obtain the bond or assigned-savings security at the normal $6,000 amount, subject to the higher judgment-based amount, and establish the separate insurance or assigned-account financial responsibility.
- Complete and notarize the application, keep every document under the exact legal business name, and pay the fee.
Plumber certificates renew every three years. PL01, PL02, and PL04 holders need 24 approved continuing-education hours per three-year period: at least 12 hours of plumbing code, at least four hours of electrical-trade classes, and eight hours of plumbing or electrical trade classes. WAC 296-400A-028 gives that breakdown. Missing the renewal window by more than 90 days triggers reexamination.
Does Washington offer plumbing reciprocity?
Washington has reciprocal certification with Idaho for journey-level plumbers. L&I identifies Idaho on its plumber-certification page. That does not mean every Idaho license transfers automatically.
A reciprocity applicant must hold a current license or certificate from a state with an active agreement and pay the reciprocity application and certificate fees. The applicant must reside in that state when applying. WAC 296-400A-070 lists those conditions. The current reciprocity application fee is $202.10, separate from the certificate fee.
If your license comes from any other state, L&I says you may present a comparable out-of-state license or equivalent United States military experience for consideration. That is an experience review, not automatic reciprocity. Plan to document the work and take the Washington exam unless L&I determines otherwise.
Frequently asked questions
How long does PL01 take in Washington?
At least four years and 8,000 documented hours, including 4,000 hours of commercial plumbing under a certified journey-level plumber.
Can a PL01 plumber start a company with only the individual certificate?
No. A covered business needs a plumbing contractor license. The business must identify a designated certified plumber, maintain a bond or assigned savings account with a normal amount of $6,000, which can rise to $18,000 after qualifying judgments, and separately provide insurance or an assigned account for the statutory financial-responsibility limits.
Does a plumbing company also need ordinary contractor registration?
A plumbing contractor licensed under chapter 18.106 RCW is exempt from registration under chapter 18.27 RCW. Other work performed by the company can create separate licensing or registration duties.
How often does a Washington plumber certificate renew?
Every three years. PL01, PL02, and PL04 renewals require 24 approved continuing-education hours with the required plumbing-code and electrical components.
Can an Idaho journey plumber use reciprocity?
Washington has an Idaho journey-level agreement, but the applicant must meet the residency, active-license, application, and fee conditions.