License check · Washington State
How to Check a Plumber's License in Washington
In Washington, plumbing contract work must be done by a licensed plumbing contractor, and L&I says only L&I-certified plumbers can legally do plumbing work on someone else's property. Both can be looked up for free in the Department of Labor & Industries' "Verify a Contractor, Tradesperson or Business" tool. Ask for the license number, search it, and make sure the name on the record matches the name on your quote.
Published November 10, 2026 · Figures and rules checked against the sources listed at the end of this page.
The check, in six steps
- Ask for the license number. Ask the company for its Washington plumbing contractor license number, and the exact business name it is licensed under. A real contractor has both to hand.
- Open L&I’s Verify tool. Go to the Washington State Department of Labor & Industries page “Verify a Contractor, Tradesperson or Business” at secure.lni.wa.gov/verify.
- Search. The tool lets you search by name, by contractor or tradesperson license, by workers’ comp account, or by WA UBI number. The license number is the cleanest search; the business name works if that is all you have.
- Read the record. L&I says a licensed plumbing contractor is listed in the tool, and that it suspends a license when a bond or insurance policy lapses or a judgment goes unpaid. Check that the license is current.
- Match the name. The name on the record should match the name on your quote and invoice. If the quote comes from a different business name, ask why before any work starts.
- Ask who the plumber is. L&I says only L&I-certified plumbers can legally do plumbing work on someone else’s property. You can look up the individual plumber in the same tool.
We read L&I’s search page and its licensing pages. We did not run a search, so this page does not describe what a result screen looks like.
Two credentials, not one
- The company: a plumbing contractor license. L&I says that since July 1, 2021, all plumbing contract work must be performed by a licensed plumbing contractor. The older “specialty plumbing” registration is no longer valid.
- The person: a plumber certificate. L&I certifies plumbers after confirming their on-the-job hours and a passed exam, and says only certified plumbers can legally do plumbing work on someone else’s property.
Each plumbing contractor must also name a certified plumber as its designated plumber.
What stands behind the license
| Requirement | Minimum |
|---|---|
| Continuous plumbing contractor surety bond | $6,000 |
| General liability, public liability plus property damage | $200,000 plus $50,000 |
| General liability, combined single limit (alternative) | $250,000 |
L&I says it suspends a license when these requirements stop being met, for example when a bond or insurance policy is cancelled or expires, or a judgment is left unpaid. That is why the check is worth repeating on the day work starts.
What L&I does besides licensing
- Checks jobsites at random.
- Investigates complaints about plumbers.
L&I Plumber Certification: 360-902-5207, Plumbers@Lni.wa.gov.
If something does not match
- No license number offered: ask again in writing before anyone starts.
- A general contractor offering to do the plumbing: ask for the plumbing contractor license as well.
- A different business name on the quote than on the record: ask which company you are hiring.
What the job should cost once you have the right company: plumbing costs in Spokane.
Sources and dates
Every figure and rule above names where it came from and the date it was read. If a source disagrees with a quote you receive, the quote wins: it reflects your house, your pipes and this week's demand. Prices are rechecked at least every six months.
- Washington State Department of Labor & Industries, "About the Plumber Certification Program" — read November 10, 2026. Who may legally perform plumbing work; how L&I certifies plumbers; contact details.
- Washington State Department of Labor & Industries, "Plumbing Licensing Requirements" — read November 10, 2026. Licensed plumbing contractor requirement since July 1, 2021; general contractors; designated plumber; bond and insurance minimums; suspension.
- Washington State Department of Labor & Industries, "Verify a Contractor, Tradesperson or Business" — read November 10, 2026. The lookup tool and its search options. No search was run for this page.