Mo. Rev. Stat. § 644.027

Nothing in sections 644.006 through 644.150 shall be deemed to restrict, inhibit or otherwise deny the power of any city, town or village, whether organized under the general law or by constitutional or special charter, any sewer district organized under chapter 204 or chapter 249, any public water supply district organized under chapter 247, or any other municipality, political subdivision or district of the state which owns or operates a sewer system that provides for the collection and treatment of sewage, to require the owners of all houses, buildings or other facilities within a municipality, political subdivision or district to connect to the sewer system of the municipality, political subdivision or district when such sewer system is available.