Section 21. The examiners shall formulate rules relative to the construction, alteration, repair and inspection of all plumbing and gas fitting work in buildings owned, used and constructed by the commonwealth and in buildings owned, used and constructed by the University of Massachusetts Building Authority, Massachusetts Department of Transportation, Massachusetts Bay Transportation Authority, Massachusetts Port Authority, Metropolitan district commission and the government center commission and all plans for plumbing and gas fitting in such buildings shall be subject to the approval of the examiners.