Washington licenses the plumber and the plumbing business separately. Here is how to get the PL01, PL02 or PL04 certification, pass the PSI exam, and license a plumbing contractor business with L&I.
Getting a plumbing license in Washington State runs through two L&I programs: an individual plumber certification (PL01, PL02 or PL04) and, for a business, a separate plumbing contractor license. This guide walks through each step, from trainee registration through the PSI exam to the business application, with the current L&I fees and deadlines.
At a glance
- Who issues it: The Department of Labor & Industries, or L&I, runs both the individual certification and the business license.
- Journey level (PL01): At least four years and 8,000 hours, including at least two years and 4,000 commercial or industrial hours.
- Exam: PSI administers the plumbing examination; the department application fee is $202.10.
- Business license: A plumbing contractor license needs a designated plumber, a $6,000 bond and liability coverage, separate from the individual certificate.
- Homeowner exemption: You do not need a license to do plumbing work on your own residence or property.
Start by deciding which track you are on: becoming a certified plumber yourself, or licensing a company that employs certified plumbers. Both routes run through L&I, but they use different forms, fees and timelines. The Washington contractor license guide covers the state's broader construction registration system; the national contractor license guide explains how other states structure the same person-versus-business distinction.
How to get a plumbing license in Washington State
Washington licenses the person and the business separately, and neither one substitutes for the other. [1, 2, 3]
| Credential | Who or what it covers | Main question to resolve | Source |
|---|---|---|---|
| Plumber certificate (PL01, PL02, PL04) | Individual plumber | Does the category cover the proposed work? | 3, 4 |
| Plumber trainee certificate | Individual in the training route | Are supervision and experience records current? | 6 |
| Plumbing contractor license | Plumbing business | Does it have a designated plumber, bond, insurance? | 1, 2 |
There is no dollar threshold that triggers plumbing licensure the way some states set a project-value cutoff. The trigger is scope: anyone performing plumbing work for someone else needs the matching certificate, and any business advertising or performing that work needs the plumbing contractor license. The one carve-out is RCW 18.106.150, which does not require a license for plumbing work you do yourself on your own residence, farm or other property you own. [8, 9]
That exemption covers your own property, not work you perform for pay on someone else's. If you are weighing whether a project needs a licensed plumber at all, start there before assuming the homeowner exemption applies.
Choose your plumbing certification
The certification category controls which experience counts and what work the resulting certificate covers. PL01, PL02 and PL04 are the routes most applicants compare, but L&I also lists pump and irrigation (PL03), domestic well pump (PL03A), medical gas and backflow categories for narrower scopes. [3]
| Credential | Minimum qualifying experience | Scope | Source |
|---|---|---|---|
| PL01 journey level | 4 yrs/8,000 hrs (2 yrs/4,000 commercial/industrial) | All phases of plumbing construction | 3 |
| PL02 residential specialty | 3 yrs/6,000 hrs under a residential or journey plumber | Single family, duplex, apartments up to 3 stories | 3 |
| PL04 residential service | 2 yrs/4,000 hrs; first yr/2,000 hrs supervised | Service, repair, replacement in existing residential work | 3 |
PL01 is the broadest category: journey level plumbers can work in all phases of plumbing construction. The standard route requires at least four years and 8,000 hours under a certified journey level plumber, with at least two years and 4,000 of those hours in commercial or industrial installations. Keep those two hour counts distinguishable in your experience log, because a total that only shows 8,000 combined hours does not demonstrate the required commercial or industrial mix. [3]
PL02 requires at least three years and 6,000 hours under a certified residential or journey level plumber, and its scope stops at single family dwellings, duplexes and apartment buildings of three stories or fewer. PL04 covers service, repair and replacement of existing fixtures and piping in single family and duplex residences, plus drain cleaning and leak repair in any residential structure; it requires at least two years and 4,000 hours, with the first year and at least 2,000 of those hours under direct supervision of a journey level or residential specialty plumber. Neither PL02 nor PL04 should be treated as a general authorization for new or concealed residential plumbing work beyond what L&I's category description allows. [3]
If your work involves pumps, irrigation, backflow assemblies or medical gas systems, check L&I's full category list before defaulting to PL01, PL02 or PL04. Washington does not issue a separate "commercial plumbing license": PL01 journey level certification is what covers commercial and industrial scope, alongside the residential work it also allows. [3]
Become a plumber trainee first
Nearly every certification route starts with the plumber trainee certificate, which lets you log supervised hours toward PL01, PL02 or PL04. Trainees must work under the direct supervision of a journey level or certified plumber; unsupervised hours do not count. [6]
- Apply for the trainee certificate. You must be at least 16; L&I processes mailed or in-person applications and issues the certificate within about 2 to 4 weeks.
- Pay the $60 annual fee. The same amount applies to each yearly renewal.
- Work under direct supervision. Match your hours to the certification category you are pursuing, including PL04's required first-year supervision.
- Keep employer experience records. Track dates, employer information, work category and supervising plumber for each job.
- Complete 8 hours of continuing education yearly. File a notarized affidavit of experience no later than 30 days after your renewal date, with a separate affidavit for each employer. [6]
Preserve an employer's experience evidence even after you move to a new job. If you wait until you believe you have enough hours to reconstruct the record, missing documentation can be hard to recover.
L&I's own form calls this document the plumber trainee certificate. Some applicants search for a trainee card or trainee license, but it is the same document under a different name.
Pass the PSI plumbing exam
Once your trainee hours and continuing education are in order, L&I reviews your eligibility and PSI administers the exam itself. The department's examination application fee is $202.10; PSI charges a separate scheduling fee once your application is approved, so the department fee is not the full cost of testing. [5]
The journey level and residential specialty exams are closed book and come in three parts: a 100-question technical knowledge section drawn from Uniform Plumbing Code chapters 1 through 10, 15, 16 and 17; a waste and vent sizing exercise from chapter 7; and a water piping sizing exercise from chapter 6. [5]
- Assemble your experience evidence. Make sure your hour totals and work mix match the category you are applying for.
- Submit the department application and $202.10 fee. Follow L&I's current instructions for required documentation.
- Wait for L&I's eligibility decision. Your approved application is valid for one year.
- Contact PSI to schedule and pay. L&I will send scheduling instructions once you are approved; it is your responsibility to reach PSI, not the other way around. [5]
- Pay the certificate issuance fee after you pass. PL01, PL02 and PL04 issuance is $242.70. [4]
If L&I requests more evidence, respond to the specific hour or documentation gap it flags rather than resubmitting the same total. Out-of-state applicants are reviewed on an active license or equivalent U.S. military experience; hours earned with out-of-state employers or in out-of-state trainee or apprenticeship programs are not eligible toward a Washington certificate. [4, 5]
Get your Washington plumbing contractor license
A certified individual plumber is not the same as a licensed plumbing business. Since July 2021, any business that advertises, bids or performs plumbing work in Washington needs the separate plumbing contractor license, and only a licensed plumbing contractor may employ certified plumbers on plumbing jobs. [1]
- Choose a business structure and register with the Department of Revenue. Sole proprietorship, partnership, LLC or corporation each work; you will need a Uniform Business Identifier.
- Identify your designated plumber. This must be an L&I-certified plumber who is an owner, partner or full time employee of the company.
- Secure the $6,000 bond or an assigned savings account. Either option satisfies the bonding requirement.
- Obtain liability coverage. Choose $200,000 public liability plus $50,000 property damage, or $250,000 combined single limit.
- Complete and notarize the application, then submit it with the fees. Mail or in-person applications generally process in 1 to 2 weeks. [1, 2]
- Wait for the license to go active before performing plumbing work. L&I states the license must be active first; advertising or bidding ahead of that date is not permitted. [1]
The plumbing contractor application and each renewal are $148.10 for the two year term; the initial designated plumber assignment or a later change is $53.20. Keep those business transactions separate from the individual's exam and certificate payments, which run through a different fee schedule. [2, 7]
A plumbing contractor license does not double as a general construction registration. A licensed plumbing contractor who also performs non-plumbing construction work still needs to register separately as a general or specialty contractor, and a general contractor performing plumbing work still needs the plumbing contractor license and bond on top of its construction registration. [1]
Want the application done for you?
Once you have your experience, exam and designated plumber lined up, the paperwork itself is still exacting: the board wants specific forms, in a specific format, with nothing missing. The Licensing Company's License Application Processing prepares and submits the state contractor license application on your behalf. That includes an eligibility audit before anything is filed, a document checklist so you and our team track down the right pieces together, every state form prepared and reviewed line by line, submission the way the board requires, and the board's paperwork questions answered and resubmitted until the board decides.
It is a flat $999 per state application, paid up front. State fees, exam fees, background checks and fingerprinting go to the state directly, not to us. We do not promise approval, a timeline or that we will sit the exam for you; the board makes the final decision. Call 615-219-2110 to talk through whether this fits your application.
If you are not yet eligible to apply on your own experience, a qualifying agent is the other route: a qualifying agent qualifies the company as an owner or full time employee who supervises the work, which lets the business operate while you build your own hours toward certification. Start a qualifying agent conversation if that fits your situation better than applying solo today.
Washington plumbing license fees
The fee rule below, effective July 1, 2026, controls the contractor license and renewal figures. It supersedes an inconsistent renewal number that still appears on L&I's general licensing-requirements page; the dated rule is the authority. [2, 7]
| Charge | Amount | Condition | Source |
|---|---|---|---|
| PL01, PL02 or PL04 issuance or renewal | $242.70 | Individual certificate, 3-year term | 4 |
| Department examination application | $202.10 | Separate PSI scheduling fee applies | 5 |
| Plumbing contractor application | $148.10 | Two year business license | 2, 7 |
| Plumbing contractor renewal | $148.10 | Every two years | 7 |
| Designated plumber fee | $53.20 | Initial designation or a change | 2, 7 |
| Plumber trainee certificate | $60 | Annual | 7 |
| Temporary permit | $100.30 | Valid 120 days | 7 |
| Replacement certificate or license | $27.20 | Lost or damaged document | 7 |
| Reinstatement, residential or journey certificate | $324.50 | Lapsed certificate | 7 |
| Plumbing contractor bond | $6,000 | Face amount, not a premium | 1, 2 |
| Plumbing contractor liability coverage | $200,000 public plus $50,000 property, or $250,000 combined | Coverage, not a premium | 2 |
Bond face amount and liability coverage are security requirements, not premium quotes; what you pay an insurer or surety depends on your own underwriting. Keep each fee tied to its own program instead of substituting a construction-registration figure for a plumbing one. [1, 2]
How long the process takes
There is no single published timeline for the whole path, because it depends on how fast you accumulate hours, but the individual steps each have their own clock. The trainee certificate itself typically mails within 2 to 4 weeks of applying. An approved exam application stays valid for one year, giving you time to schedule with PSI. The plumbing contractor license generally processes in 1 to 2 weeks once L&I receives a complete, notarized application by mail. [1, 6]
The longest stretch is the experience requirement itself: PL01 needs a minimum of four years, PL02 three years and PL04 two years of supervised hours before you are even eligible to apply for the exam. Nothing shortens that floor; the fastest path is keeping clean, complete experience records so the application and exam steps do not add delay on top of it. [3]
For a sense of scale, a trainee who logs the minimum 8,000 PL01 hours in exactly four years, then applies and schedules the exam without delay, is looking at roughly four to five years from first registering as a trainee to holding a journey level certificate. A business can move faster: once a designated plumber is already certified, the plumbing contractor application itself is a matter of weeks, not years. [1, 3]
Renew your certificate and keep up with continuing education
PL01, PL02 and PL04 certificates renew every three years on the holder's birthday; the initial certificate runs at least 25 and no more than 37 months depending on when you apply relative to your birthday. Renewal requires 24 continuing education hours, including at least 12 plumbing code hours and 4 industry-related electrical hours. [4]
The trainee certificate follows a different, annual schedule: a $60 yearly fee and 8 continuing education hours, not the certified plumber's three year cycle or 24-hour total. Keep a renewal file with your current certificate, its expiration date and education records showing both hours and subject categories, and review L&I's current renewal instructions before paying. [4, 6, 7]
Idaho reciprocity and other out-of-state applicants
L&I offers reciprocity with Idaho for journey level plumbers who hold an active Idaho journey level card; the application still requires that current credential and a government-issued photo ID. An Idaho card is a reason to use this route, not a guarantee that any Idaho license transfers automatically. [4]
Applicants from other states are reviewed on an active out-of-state plumbing license or equivalent U.S. military plumbing experience. Hours earned with out-of-state employers, or in an out-of-state trainee or apprenticeship program, are not eligible toward Washington certification regardless of the route. [4, 5]
A certified individual, whether licensed through reciprocity or Washington's own route, still works for a business that needs its own Washington plumbing contractor license, designated plumber, bond and insurance. The individual and business questions stay separate even when the individual's credential is already settled. [1, 2]
Verify a Washington plumber and business
Before hiring, check both the individual's plumber certificate and the company's plumbing contractor license through L&I's licensing lookup. Confirm the certificate category matches the work: a PL04 holder is not qualified for the commercial and industrial scope that PL01 covers. [1, 3]
A general construction registration, a passed exam or an individual's plumber certificate does not by itself show that the company holds the separate plumbing contractor license. Confirm the business credential directly rather than assuming one license implies the other. L&I's online licensing lookup shows current status, expiration and history for both records, so check that tool directly instead of relying on a business card or an invoice. [1, 3]
FAQ
Is a certified plumber also a licensed plumbing contractor?
No. The individual certificate covers the plumber's certification category; the plumbing contractor license covers the business, with its own designated plumber, bond and insurance. [1, 2, 3]
How many hours do I need for PL01, PL02 or PL04?
PL01 requires at least four years and 8,000 hours, including two years and 4,000 commercial or industrial hours. PL02 requires three years and 6,000 hours. PL04 requires two years and 4,000 hours, with the first year and 2,000 hours directly supervised. [3]
Do I need a license to do plumbing work on my own house?
No. RCW 18.106.150 does not require a license for plumbing work you do yourself on your own residence, farm or other property you own. The exemption covers your own property, not paid work for someone else. [8, 9]
What does the plumbing contractor bond cost?
The bond's face amount is $6,000. That is not a premium; your actual cost depends on your bond provider's underwriting. [1, 2]
Does an Idaho plumbing license transfer to Washington?
L&I offers reciprocity for Idaho journey level plumbers who hold an active Idaho card, subject to the department's current eligibility review. It is a route to apply through, not an automatic transfer. [4]
How long does the whole process take?
The experience floor alone is two to four years depending on the category, before the exam and certificate steps even begin. Individual processing steps, like the trainee certificate or the contractor license, typically take 1 to 4 weeks once a complete application is submitted. [1, 3, 6]
Sources
All sources below were retrieved for this guide's research on October 5, 2026.
- L&I licensed plumbing contractor program.
- L&I plumbing contractor licensing requirements.
- L&I plumber certification categories.
- L&I get or renew plumber certification.
- L&I plumber examination.
- L&I plumber trainee requirements.
- Washington plumbing fee rule, WAC 296-400A-045.
- L&I about the plumber program.
- RCW 18.106.150, homeowner exemption.
Plan your plumbing license or qualification
Whether you are closing in on your own PL01, PL02 or PL04 certificate or licensing a plumbing business, bring your paperwork, experience records and designated plumber plan into one application rather than filing piece by piece. The Licensing Company can help you evaluate the path, including the License Application Processing service described above. Call 615-219-2110 or start your qualifying agent inquiry.
Disclaimer: This article is provided for educational and informational purposes only. It does not constitute legal advice, licensing guidance, or an offer of services. Licensing requirements vary by jurisdiction. For specific compliance questions, contact The Licensing Company for a confidential consultation.