Which of the following is a distinct, separate credential from the base Journeyman Plumber certification in Washington, requiring its own exam?
Not quite. The answer is A: Backflow specialty plumber certificate (PL30)
Washington issues the Backflow (PL30) specialty as its own certificate, tested by its own 55-item, closed-book exam, and it is limited to maintenance and repair of existing backflow assemblies inside a building (it also requires an active Department of Health backflow assembly tester certification). It is not bundled into the base journeyman license. Master electrician and general contractor registration are different license categories, and apprentice/trainee registration is a prerequisite status, not a credential earned by exam.
Reference: WA L&I / PSI L&I Plumber Certification page; PSI Candidate Information Bulletin (Backflow (PL30) specialty certificate and exam)
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