In order to provide effective protection of the public health, the Plumbing Board may by rule prescribe limitations on the nature of alteration to, extension of, or connection with, the said water distribution system initially established by a licensed plumber which may be performed by a person licensed hereunder. The commissioner may by rule in appropriate instances require filing of plans, blueprints and specifications prior to commencement of installation. The installation of water heaters shall not constitute water conditioning installation and consequently such work shall be accomplished in accordance with the provisions of sections 326B.42 to 326B.49.