Directs the department to separately identify each contractor registered under chapter 18.27 RCW that notifies the department that it will do plumbing work and the department shall issue a unique contractor registration to those contractors so they can be identified as authorized to do plumbing work. The department may impose an additional fee on the contractor's registration for a contractor that will do plumbing work that is necessary to cover its costs to issue a unique contractor registration to those contractors and maintain appropriate records to identify those contractors. No contractor, except a registered plumbing contractor, whether registered or not, may advertise, offer to do, or do plumbing work in violation of this act.