(1) Journey level plumber (PL01): A journey level plumber may work on all phases of plumbing projects including residential, commercial and industrial worksite locations.

(2) Residential specialty plumber (PL02): Installation, maintenance and repair of all phases of plumbing for residential structures.

(3) "Residential service plumber (PL04)" is limited to performing residential service in single-family dwellings and duplexes and can only repair or replace previously existing fixtures, piping, and fittings that are outside the interior wall or above the floor. Residential service plumbers may not perform electrical work described in RCW 19.28.091(8) that is incidentally, directly, and immediately appropriate to the like-in-kind replacement of household appliance or other small household utilization equipment that requires limited electric power and limited waste and/or water connections.

(4) Backflow specialty plumber (PL30): Maintenance and repair of backflow assemblies located within a residential or commercial building or structure. For the purposes of this subsection, "maintenance and repair" includes cleaning and replacing internal parts of an assembly, but does not include installing or replacing backflow assemblies. A plumber trainee must have a PT31 certificate in order to work as a backflow specialty plumber under the supervision of a certified backflow specialty plumber, certified residential specialty plumber or certified journey level plumber. PT31 trainee requires one hundred percent supervision.

(5) Pump and irrigation specialty plumber (PL03): Installation, maintenance and repair of equipment that is used to acquire, treat, store, or move water suitable for either drinking or other domestic purposes, including irrigation or to a domestic water pumping system consisting of the pressurization, treatment, and filtration components of a domestic water system consisting of: One or more pumps; pressure, storage, and other tanks; filtration and treatment equipment. For the purposes of this subsection, if located within the interior space of a residential structure as stated in RCW 18.106.010 (14)(c), only the equipment and piping defined by RCW 18.106.010 (14)(c) are included in this specialty and other parts of the system must be worked on by the appropriate certification.

(6) Limited volume domestic pump specialty plumber (PL03A): Installation, maintenance and repair of equipment that is used to acquire, treat, store, or move water suitable for either drinking or other domestic purposes on pumping systems not exceeding one hundred gallons per minute. A domestic water pumping system consisting of the pressurization, treatment, and filtration components of a domestic water system consisting of: One or more pumps; pressure, storage, and other tanks; filtration and treatment equipment. For the purposes of this subsection, if located within the interior space of a residential structure as stated in RCW 18.106.010 (14)(c), only the equipment and piping to stated equipment in this locked room can be worked on by this certification; other parts of the system must be worked on by the appropriate certification.

(7) Plumber trainee (PT00 and PT31): Is an individual learning the trade or craft of plumbing. Trainees are required to have and maintain a valid plumber's training certificate. Trainees will be accredited for those hours worked within the scope of their supervising plumber. Any plumber trainee may perform plumbing work within the scope of their supervising journey level or specialty plumber. A trainee must keep a record of the hours worked as a trainee as required by WAC 296-400A-120(3). A trainee performing electrical work described in RCW 19.28.091(8) that is incidentally, directly, and immediately appropriate to the like-in-kind replacement of household appliances or other small household utilization equipment that requires limited electric power and limited waste and/or water connections must be supervised by a journey level plumber (PL01) or residential specialty plumber (PL02). In accordance with RCW 19.28.161(3), the trainee performing electrical work must be under the direct supervision of a PL01 or PL02 certified plumber who is on the same job site as the trainee and remote supervision or supervision by residential service plumbers is not permitted.

(8) Certified journey level electricians, certified residential specialty electricians, or electrical trainees (EL01 and EL02): According to RCW 18.106.150 (2)(b), a current plumbing certificate of competency or plumber trainee card is not required for: Certified journey level electricians, certified residential specialty electricians, or electrical trainees working for a general or residential specialty electrical contractor (EC01 or EC02) and performing exempt work under RCW 18.106.150(8). A plumber trainee must have an electrical trainee (ET00) certificate in order to work with a journey level electrician or residential specialty electrician.

The plumbing work must be directly and immediately appropriate to the like-in-kind replacement of a household fixture or its component(s) that requires limited power and waste/water connections.

An example would be replacing the heating element (a component) of an electric hot water heater. An electrician performing a like-in-kind replacement of an electric hot water tank could only disconnect and then reconnect the water supply lines to the tank and drain line from the temperature and pressure relief valve. Gas hot water tanks are not part of the electrician's exemption.