Mo. Rev. Stat. § 341.120
The county commission shall in the establishment of the department of plumbing and sewer inspection provide the necessary personnel and employees and shall provide suitable quarters for such department and shall make adequate appropriation for the necessary equipment, facilities and operating expenses of such department. The compensation of the supervisor of the department of plumbing and sewer inspection shall be fixed by the county commission and shall be payable pro rata monthly by the county commission out of the county treasury and he shall appoint with the approval of the county commission the necessary assistant inspectors who shall receive such salaries as may be determined by the county commission payable in the manner aforesaid, and who shall not engage or work in the business of plumbing or drainlaying during the period of their employment.
§ 341.120, RSMo