Missouri private well rules
The Missouri Geological Survey's Well Installation Section (Department of Natural Resources) administers the Water Well Drillers Law and issues permits to drillers and pump installers.
Who licenses well work in Missouri
Sections 256.600 to 256.640 RSMo set well construction standards and require drillers and pump installers to have permits. The rules are in 10 CSR 23.
Who may work on a well pump
Drillers and pump installers who charge for their work must hold a Missouri permit.
Landowners who install their own pump are exempt from the permit requirement but must still follow the rest of the well rules.
Source: Paid installers need a permit
Does the state require well testing?
The Missouri health department offers private well testing as a public health service but not specifically for real estate deals; buyers and sellers should use a private lab.
The Department of Health and Senior Services recommends testing a private well at least once a year and whenever the well is serviced.
The DNR well FAQ recommends bacteria testing every year and heavy metals every three years.
Sources: No state testing for sales; Heavy metals every three years
Getting your water tested in Missouri
The Missouri State Public Health Laboratory offers both bacteria and chemical testing of private well water.
The state lab tests for total coliform and E. coli, and iron bacteria testing is available by special request.
A "new well series" chemical test covers fluoride, chloride, nitrate, sulfate, iron, manganese and lead.
The DNR FAQ tells owners to contact their local county health office for sampling instructions and containers.
Sources: State Public Health Laboratory tests well water; Containers from county health office
Disinfecting a well
Missouri DNR says disinfection is needed after a positive bacteria test, flooding, or work on the well such as a pump replacement.
DNR recommends using a licensed well contractor to disinfect a well and gives step-by-step instructions for owners who do it themselves.
DNR warns that chlorinating a well several times a year corrodes the casing.
Source: When disinfection is needed
Plugging an unused well
Abandoned wells must be plugged and this usually falls to the landowner, who may plug wells on their own property. A hired person must hold a DNR permit.
Plugging must be registered with DNR within 60 days. DNR then sends the landowner a registration number, which some lenders ask for at sale or refinance.
Checking a contractor's license
Permitted contractors and existing well records are available online through DNR.
Permit numbers should be shown on drilling equipment, and owners can ask to see a permit card or call the Well Installation Section.
Sources: Online list of permitted contractors; Check the permit
Common questions
Does Missouri require private well owners to test their water?
The Missouri health department offers private well testing as a public health service but not specifically for real estate deals; buyers and sellers should use a private lab.