After a well floods
Texas A&M AgriLife Extension says to assume a flooded well is contaminated until it has been disinfected and tested.
After a flood
Texas A&M AgriLife Extension says not to use flooded well water for drinking, cooking, ice, brushing teeth or even bathing until you know it is safe.
Texas A&M AgriLife Extension warns against turning on a pump or electrical system that was under water; have an electrician check the wiring once it dries.
EPA says wells more than 10 years old or less than 50 feet deep are likely contaminated after a flood even with no visible damage.
EPA says drilled, driven or bored wells are best disinfected by a well or pump contractor because they are hard for owners to disinfect thoroughly.
EPA advises having the water tested for bacteria 7 to 10 days after disinfection, and warns a flooded area well may not be safe for months.
Texas A&M AgriLife Extension notes that disinfection does not remove fuels, pesticides or heavy metals; suspected chemical contamination needs special testing.
When flooding is coming, the Missouri DNR tells owners to secure the well cap, turn off power, and seal vents and openings with silicone caulk until floodwater recedes.
Sources: Assume it is contaminated; Older and shallow wells; Missouri: before the flood
Common questions
Is my well water safe after a flood?
Texas A&M AgriLife Extension says to assume a flooded well is contaminated until it has been disinfected and tested.