The provisions of sections 326B.50 to 326B.58 that require licenses to engage in the work or business of water conditioning installation, and the provisions that provide for the examination of applicants for such licenses, do not apply to master plumbers and journeyworker plumbers licensed under the provisions of sections 326B.42 to 326B.49. In all areas of the state except in cities or towns with a population of more than 5,000 according to the last federal census, the provisions of sections 326B.50 to 326B.58 that require licenses to engage in the work or business of water conditioning installation, and the provisions that provide for the examination of applicants for such licenses, do not apply to restricted master plumbers and restricted journeyworker plumbers licensed under the provisions of section 326B.475.