Before you hire
Checking a Seattle plumber's license
Two licenses matter when you hire a plumber in Seattle: the one the worker carries and the one the company holds. I check both before anyone starts.
The worker and the company
State law bars anyone from doing plumbing, or offering to, without a plumber certificate and photo ID in their possession. The certificate can be journey level, specialty, residential service, a temporary permit or a trainee certificate. (RCW 18.106.020)
The business needs its own license too. L&I says that since July 2021 a plumbing company must be licensed as a plumbing contractor. (L&I)
Which certificate covers what
- Journey level (PL01): qualified for every phase of plumbing construction. Getting there takes four years or more, at least 8,000 hours, working as a plumber trainee. (L&I)
- Residential (PL02): limited to installing, maintaining and repairing plumbing in single-family homes, duplexes and apartment buildings of three stories or fewer. (L&I)
- Residential service (PL04) and medical gas piping installer (MG01) are separate certificates. (L&I)
- Washington and Idaho honor each other's journey level plumber certificates. (L&I)
What a licensed plumbing company has on file
- A bond of six thousand dollars, set by state law for plumbing contractors. (RCW 18.106.410)
- Liability insurance of $200,000 public liability and $50,000 property damage, or a $250,000 combined single limit. (L&I, read Oct 18, 2026)
- An application fee of $148.10, plus $53.20 to assign the company's designated plumber. (L&I, read Oct 18, 2026)
L&I's Verify tool shows a company's registration, workers' comp account, safety violations, and lawsuits against its surety bond. (L&I) I look plumbers up on L&I Verify.
Seattle fees on top of the state rules
- Seattle's 2026 business license fee for $0 to $19,999 of Seattle taxable revenue is $73. (City of Seattle, read Oct 18, 2026)
- L&I's plumbing contractor specialty includes liquid and fuel gas piping. (WAC 296-200A-016(42)) Seattle adds its own gas piping mechanic license, at $139 a year in 2026, with $62.55 for each license exam. (Seattle 2026 Fee Subtitle, read Oct 18, 2026)
What I ask on the first call
- What is your plumber certificate number, and which type is it?
- What is the company's plumbing contractor license number? I will look it up on Verify before the visit.
- Who holds the certificate on this job, and will that person be here?
- If the job touches gas lines: who holds the Seattle gas piping mechanic license?
- Who pulls the permit, and is it in the written price?
Next
See how to hire a Seattle plumber and what a fair plumbing quote looks like.
Sources
We read each source on October 18, 2026. Rules and prices change, so check the linked page before you rely on a number.
- Chapter 18.106 RCW, plumbers
- Washington L&I: Licensed plumbing contractor
- Washington L&I: Plumber certification
- Washington L&I: Plumbing contractor licensing requirements
- Washington L&I: Verify a contractor, tradesperson or business
- Washington L&I: Verify a Contractor, Tradesperson or Business
- City of Seattle: Business license tax certificate
- WAC 296-200A-016, contractor specialties
- Seattle SDCI 2026 Fee Subtitle (PDF)
Written by the Seattle Emergency Plumbers team. We list businesses; we do not employ, bond or insure them. Spot a mistake? Use the claim page to tell us.