Short definition
The Washington L&I plumbing license is the state-level certification required for anyone doing plumbing work in WA. The Department of Labor & Industries administers the program through several license types, with PL01 (Journey Level) the most senior and PL02 (Residential) the most common for home plumbing work. Verify any plumber’s license at L&I’s online verification site before hiring.
What it is
WA is unusual in administering plumbing licensing at the state level — most other US states delegate licensing to counties or cities. WA L&I’s Plumber Certification Program issues several license types:
- PL01 — Journey Level Plumber. 4+ years (≥ 8,000 hours) of supervised experience, with at least half in commercial/industrial work. Most senior license. Can do any plumbing scope, residential or commercial.
- PL02 — Residential Plumber. 3+ years (≥ 6,000 hours) experience. Limited to residential work. Most common license for home plumbing.
- PL03 — Pump and Irrigation. 2+ years (≥ 4,000 hours). For well pump and irrigation work.
- PL03A — Domestic Well. 1+ year (≥ 2,000 hours). For domestic well-pump installation specifically.
- PL04 — Residential Service Plumber. 2+ years (≥ 4,000 hours), first year under direct journey-level supervision. Service repair and replacement scope only — no new construction.
- PL30 — Backflow. Active BAT (Backflow Assembly Tester) certification from WA Department of Health. For installing and testing backflow assemblies.
- MG01 — Medical Gas Piping Installer. For hospitals and medical-facility gas piping.
Reciprocity: WA holds reciprocal licensing with Idaho — an Idaho-licensed plumber meeting WA equivalency can be certified in WA without re-examination.
All plumbing work in WA must be done by an L&I-certified plumber, with one major exception: a homeowner doing work on their own owner-occupied single-family dwelling (the homeowner-permit path). The work still requires permits and inspections, but the homeowner can be the responsible party.
A plumbing contractor (the company) must hold contractor registration (SCBR) and bond + insurance through L&I, in addition to having licensed individual plumbers on staff. The individual plumber’s PL01/PL02/etc. license and the contractor’s SCBR are separate registrations.
Why it matters to a homeowner
Three reasons.
Verify before hiring. L&I publishes online verification at secure.lni.wa.gov/verify/. You can look up a plumber’s individual PL card or a contractor’s SCBR by name, license number, or business name. Before signing any contract, verify both the contractor’s SCBR and the actual individual plumber’s certification.
Unlicensed work can void insurance. Hiring an unlicensed handyman to swap a water heater is illegal in WA, voids the permit (since you can’t get one), and can void your homeowner insurance if the heater later leaks. The license verification is a five-minute check that protects against major downstream costs.
The card present on-site matters. A plumbing company with a licensed PL01 owner doesn’t mean every employee is licensed. Some companies do illegal work using unlicensed laborers under nominal supervision. WA requires the licensed plumber on-site for licensed work; you can request to see the card during the visit.
When a quote comes in significantly below market, check the licensure. The unlicensed-handyman discount usually doesn’t include warranty, permits, insurance protection, or much accountability when something goes wrong. The “savings” usually evaporate at the first problem.
When you’ll encounter this term
- Hiring a plumber and verifying credentials.
- A permit application requiring the contractor’s L&I license number.
- A real estate inspection report flagging unlicensed work.
- An insurance claim requesting verification of licensed installer.
Common variants and disambiguation
- PL01 vs. PL02 vs. PL04. PL01 = full journey, any work, any building. PL02 = residential only. PL04 = service work only (no new construction).
- L&I license vs. contractor registration. A plumbing contractor must hold contractor registration (SCBR) plus bond and insurance through L&I. An individual plumber needs a personal PL01/PL02/etc. card. Different registrations.
- L&I license vs. city license. WA pre-empts most city licensing for plumbers. Seattle, Tacoma, etc. don’t issue their own plumbing licenses on top of WA L&I. (Side sewer work in Seattle is the exception — SPU registration is on top of L&I licensure.)
Washington note
L&I’s Plumber Certification Program at https://lni.wa.gov/licensing-permits/plumbing/plumber-certification publishes the full requirements, exam content, and renewal cycles. The verification portal at https://secure.lni.wa.gov/verify/ lets homeowners look up any individual plumber or registered contractor.
For specific WA scenarios:
- Hiring a plumber for any work: verify PL01 or PL02 card via L&I online.
- Hiring an unlicensed handyman to replace a water heater: illegal in WA. Voids permit (since you can’t pull one with an unlicensed installer) and potentially voids homeowner insurance.
- Verification mismatch: the contractor company is registered, but the individual showing up doesn’t have a current PL card. Homeowner can require proof or refuse the work.
- Out-of-state contractor (Idaho reciprocal) doing WA work: must be PL01-equivalent and properly registered to operate in WA.
For licensed plumbers specifically, PL30 backflow certification is held in addition to PL01/PL02 — many WA plumbers hold both, allowing them to install and annually test backflow assemblies under WAC 246-290.
FAQ
How do I verify a plumber’s license in Washington?
Use L&I’s online verification at secure.lni.wa.gov/verify/. You can look up an individual plumber by name or PL card number, and a contractor by business name or SCBR number. Both should be active for the work to be legal.
What’s the difference between PL01 and PL02 in WA?
PL01 is the senior journey-level license — any plumbing scope, residential or commercial, any building type. PL02 is the residential plumber license — limited to residential work. Both require multi-year supervised experience plus an exam. For most home plumbing work, PL02 is sufficient; commercial buildings need PL01.
Can I do my own plumbing work in WA without a license?
Yes, on your own owner-occupied single-family residence. The homeowner-permit path lets you pull permits and do the work yourself. The work still must pass inspection. Note: this exemption doesn’t extend to rental properties, ADUs that aren’t your primary residence, or work for friends/family on their homes.