The Missouri Department of Health and Senior Services (DHSS) has no requirements regarding the testing of private drinking water sources. Public drinking water systems are tested regularly for a variety of contaminants. However, private drinking water sources are not regulated in the state of Missouri. It is up to the parties involved in any real estate activities to decide if they would like the well water tested.

Well installation contractors are required to follow the Department of Natural Resources (DNR) Water Well Drillers Act, sections 256.000 to 256.640 RSMo and the rules written that enforce this statute establishing well construction standards aimed to protect Missouri's groundwater. More information on DNRs Water Well Drillers Act can be found at: https://dnr.mo.gov/geology/geosrv/wellhd/wellsanddrilling.htm.