Washington plumber licenses, bonds and insurance, explained

The plumber: an L&I certificate

Nobody may do plumbing for pay in Washington without an L&I certificate: journey level, specialty, residential service, temporary or trainee. The plumber has to carry it with photo ID, and trainees work under supervision. (RCW 18.106.020)

This is the credential that speaks to skill. Washington does not test general contractors to register, but L&I does test and license plumbers. (L&I F625-084-000)

The company: a plumbing contractor license

Since July 1, 2021, it has been unlawful to advertise, bid or do plumbing work without a plumbing contractor license. The old "specialty plumbing" registration stopped being valid that day. A licensed plumbing contractor does not have to register under the general contractor law, though it can choose to so it can take non-plumbing work. (RCW 18.106.400) (L&I)

A licensed or registered contractor also may not subcontract plumbing to anyone unlicensed. (RCW 18.106.020)

Bond and insurance

• Bond: $6,000, filed with L&I when the company applies for its plumbing contractor license. (RCW 18.106.410, read Oct 18, 2026) A plumbing contractor that also registers as a general contractor carries the $30,000 general bond on that registration. (L&I)
• Insurance, per the statute: $50,000 for property damage, $100,000 for injury or death to one person, and $200,000 for more than one person. (RCW 18.106.420, read Oct 18, 2026)
• Insurance, per L&I's requirements page: general liability of $200,000 public liability and $50,000 property damage, or $250,000 combined single limit. (L&I)

The two sources give different minimums. Ask for the certificate and read the limits on it.

What the bond pays

The plumbing bond uses the same coverage wording as the general contractor bond: unpaid labor, taxes and suppliers, plus amounts a court awards for breach of contract, including improper work. A homeowner has two years from substantial completion or abandonment to sue, and claimants other than homeowners can take no more than half the bond. (chapter 18.106 RCW) (RCW 18.27.040) At $6,000, the bond covers a small repair better than a repipe. (RCW 18.106.410)

What these leave out

• Workers' comp. Employers buy it from L&I or self-insure; Washington allows no private workers' comp. (L&I)
• Liens. Unpaid suppliers or workers can lien your property. Ask for lien releases on a big job. (L&I F625-084-000)

Doing it yourself in King County

In Seattle and unincorporated King County, you may do plumbing on your own home, with unpaid help from friends or relatives. Once you pay someone, the installer must be a certified journeyman plumber and a registered contractor or employed by one. (King County)

How to check

1. Look up the company's plumbing contractor license on L&I Verify.
2. Ask the plumber at your door for the certificate card and photo ID, and look the name up on Verify too. (RCW 18.106.020)
3. Ask for the insurance certificate and check the business name, dates and limits.

Back to how to hire an emergency plumber or the plumber red flags.