Sections 341.090 to 341.220 shall be known as the “Uniform Plumbing Code”, and shall apply to counties of the first class only. Sections 341.090 to 341.220 shall become effective in any county of the first class only upon a finding by the county commission of such county that it is necessary for the promotion of the public health and safety of such county. From and after the making of such finding and the entry of same upon the records of the county commission sections 341.090 to 341.220 shall be in full force and effect in such county and not otherwise.