Plumber Examination

Examination is the final step to become a certified plumber in Washington.

In-state applicants & plumber trainees

Before signing up for your examination, submit your affidavits of experience documenting your required years and hours of experience, and complete your continuing education requirements. Once these are approved, you can submit your application to sign up to take the exam for your certification level.

Note: Hours of experience from out-of-state employers and trainee or apprenticeship programs from other states are not eligible for Washington certification.

Out-of-state applicants

Washington has reciprocal certification with Idaho for journey level plumbers. All other plumbers working in Washington must pass the Washington state plumber examination to work in the state. To apply, you will need to submit a copy of your government-issued photo ID and your out-of-state license for review by the plumber certification program. U.S. military members can show equivalent experience for consideration.

Once your credentials are approved, you can submit your application to sign up for an upcoming exam. To get started, request more information, or apply for a reciprocal certificate, email or call (360) 902-5207.

Temporary permit for out-of-state plumbers

After your out-of-state credentials are approved, plumbers with a current, unexpired out-of-state license can apply for a one-time 120-day temporary permit. This permit allows plumbers to work at their current certification level while waiting to take the Washington exam. There is a $79.85 fee for this permit. If you have ever held a temporary permit, or a Washington state plumber or trainee certification, you are not eligible for a temporary permit.

Application Information

We accept exam applications online or by mail. Your application and non-refundable exam fee of $160.85 must be received and processed by L&I at least two weeks before the exam date. Applications are processed on a first-come, first-served basis. Examination dates requested are not guaranteed. Seats for the exam are limited and are assigned in in the order that applications are received. Applicants are advised to send in their application as early as possible.

Apply by mail:
To apply for examination, print the Plumber Certification Application and follow the directions on the form.

Note: Be sure to include only the applicant’s name, address, Social Security number, and phone number on the application, not the employer’s information.

For exam dates and locations view Plumbing Examination Dates and Locations (F627-027-000).


If you are unable to take the exam on the date scheduled, or you need to reschedule, email You can also send your request in writing to:
Plumber Certification
P.O. Box 44470
Olympia, WA 98504

We must receive your request to reschedule before the date of your exam. See our Plumber Examination Dates and Locations form for options on our current dates and locations. 

If you miss the exam

If your request to reschedule is not received before the scheduled exam date, or you fail to show for the exam, your exam fee will be forfeited. If you miss your exam without giving proper notice, you will have to resubmit your application and pay an additional examination fee ($160.85).

About The Exam

Washington state plumber examinations are based on the 2015 Uniform Plumbing Code (UPC) and include amendments as adopted by the Washington State Building Code Council. These amendments play a vital role in how plumbing installations are performed.

To buy the 2015 Uniform Plumbing Code books or Washington State amendments contact Washington Association of Building Officials (WABO) at 360-628-8669. You can also view and print the Washington State Amendments for free at the Legislature's website<link> or you can download a PDF of the amendments<link>.

Exam content and structure

Journey level and residential exams

The Journey Level and Residential Specialty exams are closed book. Tables 702.1, 610.3, 610.4, and 610.10 are provided with the exam. Table 703.2 is not provided. The exams consist of three parts:

  • Technical and general trade knowledge: This part of the exam has 100 questions on plumbing code taken from Chapters 1 through 10, 15, 16, and 17 of the UPC and amendments.
  • Code application knowledge for waste and vents: This part of the exam is a waste and vent sizing exercise taken from Chapter 7 of the UPC and amendments. A drawing of a building is provided, showing elevated views of plumbing fixtures along with the illustrated piping for the vents, waste, and cleanouts that are needed to drain and vent these fixtures. You will provide fixture units and pipe sizes. Use minimum sizing as allowed by the UPC along with maintaining aggregate venting.
  • Code application for water piping: This part of the exam is a water pipe sizing exercise taken from Chapter 6 of the UPC and amendments. A drawing of a building is provided, showing elevated views of plumbing fixtures along with the illustrated piping for the hot and cold-water distribution system. You will provide the fixture units and pipe sizes. Use minimum sizing as allowed by the UPC.

Backflow specialty exam

This exam contains questions relating to safety, regulatory, operation, and troubleshooting of backflow prevention assemblies.

Domestic Pump and Pump & Irrigation Specialty Exam

This exam contains questions taken from Chapters 2, 3, 6, and 16 of the UPC and amendments.