Mo. Rev. Stat. § 701.055
Property owners may install, modify or clean their own on-site sewage ...
701.055. Property owners may install, modify or clean their own on-site sewage disposal system in compliance with requirements, no permit required for cleaning. — 1. Nothing in sections 701.053 to 701.055 shall preclude property owners from installing, modifying or repairing their own on-site sewage disposal system as long as they comply with the provisions of sections 701.025 to 701.059 .
2. Nothing in sections 701.025 to 701.059 shall be construed so as to require a property owner to obtain a permit or to obtain registration as an on-site sewage disposal system contractor in order to clean that property owner's on-site sewage disposal system.
(L. 1994 S.B. 446 § 701.053 subsecs. 6, 7)