Becoming a Plumber

You must be certified by the Washington State Plumber Certification Program to work in the plumbing trade in Washington.

The plumbing trade includes all:

  • Potable water building supply and distribution pipes.
  • Plumbing fixtures and traps.
  • Drainage and vent pipes.
  • Accessories (appurtenances) within the property lines of the premises.
  • Medical gas and medical vacuum systems, and
  • Water heaters.

Except for domestic pump and pump and irrigation systems, certification is not required to install plumbing systems outside of a building (e.g., water lines connected directly to municipal water mains, sewer line connections, etc.).

Certification Requirements

To become a certified journey level or specialty plumber in Washington, you must typically begin as a plumber trainee. Washington has reciprocal certification with Idaho for journey level plumbers. All other out-of-state plumbers can present a comparable license from another state or show equivalent experience in the U.S. military for consideration.

The categories below list the required experience for each plumber certification level in Washington.

Journey Level and Medical Gas

Journey level plumber (PL01) is qualified to work in all phases of plumbing construction.

  • Four years or more (at least 8,000 hours) working as a plumber trainee under the supervision of a certified journey level plumber.
    Note: Two years or more (at least 4,000 hours) must be spent working in commercial or industrial installations

Medical gas piping installer (MG01) is a journey level plumber who is also qualified to work on medical gas piping systems that deliver oxygen, nitrous oxide, high-pressure nitrogen, medical compressed air, medical vacuum systems, etc.

  • Must complete at least 32 hours of training in an L&I approved medical gas training course
Residential

Residential (PL02) is limited to installation, maintenance, and repair of plumbing in single-family dwellings, duplexes, and apartment buildings which do not exceed three stories.

  • 3 years or more (at least 6,000 hours) working in the specialty under supervision of a certified residential or journey level plumber.
Pump & Irrigation and Domestic Well

Pump and irrigation (PL03) is limited to installation, maintenance, and repair of equipment that is used to acquire, treat, store, or move water suitable for drinking or irrigation purposes.

  • 2 years or more (at least 4,000 hours) working in the specialty under supervision of an appropriate certified plumber (excluding PL03A and PL30).
    Note: Working in this trade also requires electrical certification. See the steps to obtain a combination plumber/electrical certification.

Domestic well (PL03A) is limited to installation, maintenance, and repair of equipment that is used to acquire, treat, store, or move drinking or irrigation water using a pump not exceeding 100 gallons per minute or 7.5 horsepower, single phase (see for electrical requirements).

  • 1 year or more (at least 2,000 hours) working in the specialty under supervision of a certified plumber, (excluding PL30).
    Note: Working in this trade also requires electrical certification.
Backflow

Backflow (PL30) is limited to maintenance and repair of existing backflow prevention assemblies within a building. It does not include installing or replacing backflow prevention assemblies.

  • An active BAT (Backflow Assembly Tester Certification) issued by the Washington State Department of Health is required.