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. Applications are processed on a first-come, first-served basis. 

Plumber Certification exams are administered by PSI, with testing locations available across the United States. For information on preparing for the exam, what to expect when taking the exam, testing locations in Washington, and exam content, download the Plumbing Examinations Candidate Information Bulletin

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).


Candidates will need to apply for eligibility with the Department before being allowed to take an examination. Approved applications are good for one year. Once your application has been approved Plumber Certification will send you a letter with detailing how to contact PSI to schedule your exam. You will also receive an email confirmation from PSI. It is your responsibility to contact PSI to pay and schedule for the examination.  

There will also be a scheduling fee you will be required to pay to PSI in order to schedule your examination. Examination fees are not refundable or transferable. The examination fee is valid for one year from the date of payment.


If you are unable to take the exam on your scheduled date, or you need to reschedule, you will need to contact PSI 2 days before the scheduled examination date at 855-340-3910. If you do not contact PSI at least 2 days prior to your exam date you scheduling fee will be forfeit. 

Note:  A voicemail or email message is not an acceptable form of cancellation.  Please use the PSI Website or call PSI to speak directly to a Customer Service Representative.

If you miss the exam

If you miss your appointment with PSI, you will not be able to take the examination as scheduled, further you will forfeit your scheduling fee, if you:

  • Do not cancel your appointment 2 days before the scheduled examination date;
  • Do not appear for your examination appointment;
  • Are not checked in by your scheduled start time;
  • Do not present proper identification when you arrive for the examination.


If you fail to pass the exam (and you are still in your 1 year approval timeframe), you will be required to wait 2 weeks (14 calendar days) from your last examination before you will be able to schedule another date with PSI. 

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.