About the Plumber Certification Program

We certify plumbing professionals and ensure they meet state requirements to provide safe plumbing for the public.

Only L&I-certified plumbers can legally perform plumbing work on someone else’s property. Property owners can perform their own plumbing work on properties they own.

  • We certify plumbers after confirming they’ve had the appropriate number of hours of on-the-job training, and pass the required exam.
  • We randomly check jobsites to make sure certified plumbers are performing the work and are properly supervising plumber trainees.
  • We investigate complaints about plumbers.
  • At any given time, we regulate more than 6,000 plumbers, 4,000 plumber trainees and 600 medical gas installers.

Partnering with plumbers
The Advisory Board of Plumbers meets quarterly to address issues facing plumbers and the plumbing industry.

For more information, contact the Plumber Certification Program.
Email: Plumbers@LNI.WA.GOV
Phone: 360-902-5207