Mo. Rev. Stat. § 91.595
All cities in the state under special charter and which have or may hereafter have a population of not less than three thousand and not more than ten thousand inhabitants and which now own and operate or may hereafter own and operate a waterworks system may, and are hereby authorized and empowered to, issue revenue bonds, which shall be payable solely from the revenues derived from the operation of such utility by the municipality and not a general obligation of such city, for the purpose of providing funds for the repair or improvement of any such system, including the pumping and distribution facilities thereof, or the replacement of any part thereof, or for the extension of any such system within or without such city as such expenditures are now or may hereafter be allowed by law, and for the acquisition of all necessary easements and rights-of-way which such extension or improvement may require, and for the purchase and installation of all necessary equipment and materials for adding additional pumping or distributional facilities to any such system including the purchase of any existing distributional facilities now or hereafter allowed by law.
§ 91.595, RSMo