Mo. Rev. Stat. § 341.210
Sections 341.090 to 341.220 shall not be construed as limiting or otherwise restricting the existing authority of any city, town or village in such counties, and the provisions hereof shall not be applicable within the limits of any such municipality which has provided or which may hereafter provide by ordinance for the regulation of plumbing, sewer, and water installations therein; provided that such ordinances shall not be in conflict with this law or the regulations adopted hereunder; provided further, that any plumber or drainlayer who has been licensed by the board of plumbing and sewer inspection of counties subject to the provisions of sections 341.090 to 341.220, and who has deposited the required bond with said board, shall not be required to furnish an additional bond by any municipality in such counties, but the bond deposited with the county board of plumbing and sewer inspection shall be available for the protection of such municipalities, and the residents thereof.
§ 341.210, RSMo