Do you need a license to work as a plumber in Washington?
Yes. In Washington, anyone doing plumbing work must hold a state plumbing certificate or permit, and a contractor employing plumbers must be a licensed plumbing contractor. The certificates are journey level, specialty and residential service certificates, temporary permits and trainee certificates, and a trainee must be supervised by a certified plumber. Medical gas piping installation also requires a medical gas piping installer endorsement. This is RCW 18.106.020.
| What | Washington |
|---|---|
| Plumber license | State plumbing certificate and contractor license |
Source
RCW 18.106.020
Read the statute in the Revised Code of Washington (Washington State Legislature): app.leg.wa.gov.
Checked against the statute on November 13, 2026.
This is a summary of a published statute, not legal advice. Rules change, local ordinances can add to them, and the terms of a specific lease may differ. Check the citation and speak to a lawyer before acting.
How Seayora uses this rule
A contractor on Seayora keeps each license with its issuing state, its expiry date and the last four digits of its number, and the business is warned before one lapses — on the website and both phone apps. A customer finding a pro on Seayora sees whether a license is on file.
Guides on this rule
- Contractor License Requirements by State: Every Trade — Which states require a state license for electricians, plumbers, HVAC, general and home improvement contractors, with the statute for each.
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The same question in other states
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