R.I. Gen. Laws § 5-20-35

(a) The provisions of this chapter do not apply to the installation of automatic sprinkler systems or other fire protection appliances in this state and do not apply to employees of public utilities (publicly or privately owned); provided, that any resident of Rhode Island not licensed, as provided in this chapter, desiring a license as a master plumber or journeyperson plumber who on or before August 14, 1966, presents to the department of labor and training of the state reasonably satisfactory evidence, in writing, that he or she was actively engaged in the business of plumbing as a master plumber or working as a journeyperson plumber for a master plumber in any city or town for five (5) years prior to May 16, 1966, and that he or she is at the time of presenting that evidence to the department of labor and training operating in any city or town as a master plumber or working as journeyperson plumber, shall, upon payment of a fee of five dollars ($5.00) in the case of a master plumber or one dollar ($1.00) in the case of a journeyperson plumber, have issued to him or her by the department of labor and training a certificate of license as a master plumber or a journeyperson plumber without an additional application, fee, or other condition precedent. Farms, golf courses, and nurseries performing irrigation work on their premises only shall not be required to be licensed under the chapter.

(b) Solar thermal professional. A renewable energy professional certificate (REPC) shall be issued to any person, firm, or corporation, qualified under this chapter, engaged in, or about to engage in, the business of installing solar thermal technologies. Solar thermal plumbing or mechanical work must be performed by persons, firms, or corporations properly licensed under this chapter or chapter 27 of title 28. REPC holders may advertise and bid for solar thermal work provided that they contract with persons, firms, or corporations who or that are properly licensed under this chapter or chapter 27 of title 28 to perform all related plumbing or mechanical work. The REPC shall specify the name of the person, firm, or corporation applying for it and the name of the person, who, in the case of a firm, is one of its members, and in the case of a corporation, is one of its officers, passing the examination by which he or she is authorized to enter upon or engage in business as prescribed in the certificate.

(c) Solar thermal professional€™s certificate. The Rhode Island department of labor and training shall issue a certificate of competency in the design and installation of solar thermal systems to any person, firm, or corporation who or that has received a certification from a nationally recognized, or equivalent, renewable energy certification training program and has demonstrated proof of such certification to the Rhode Island office of energy resources.

(d) Nothing in this or any other chapter of the general laws shall prohibit municipalities or water districts from using employees, or engaging the services of licensed plumbers or other contractors and/or service providers that meet certain requirements determined by the municipality or water district, for the purpose of replacing water meters or meter reading devices.