minnesota department of health

Flooding threatens private drinking water wells

Health officials urge users to protect private wells from potential flood contamination  

With the risk of flooding increasing in many parts of the state, the Minnesota Department of Health (MDH) urges private well users to prepare for the possibility that their wells might flood.  

If you get your drinking water from a private well, taking these preventative actions now may help protect that water from becoming contaminated.  

If your well is in a flood-prone area and you have time, consider contacting a licensed well contractor to check your well and make any necessary repairs or changes to help protect it from flooding. These changes may include repairing cracked or damaged casing, extending the well casing above the expected flood level, or temporarily replacing the vented well cap with a watertight cap or cover. You should also make sure that grading allows water to flow away from your well.  

If you think your well might become flooded, store a supply of clean water that will last for at least a few days. Shut off power to the well pump to avoid having floodwater pumped into your plumbing system or home. If you only have a little time before a flood, you can cover the well with a heavy plastic bag or sheeting and secure it with electrical tape. This won’t completely protect your well from contamination, but it will help reduce the amount of water and debris that could enter your well, making cleanup easier.  

If floodwater reached your well, assume your well is contaminated. Water from your well should not be used for drinking, cooking or brushing your teeth until the floodwater recedes. Also:

  • Avoid electrical shock. Do not approach a flooded well until it has been completely disconnected from its power source.
  • If floodwater covered your well or may have entered your well directly, have a licensed well contractor inspect the well, clean out sediment or debris and disinfect it with a chlorine solution. Using your well pump to remove sediment or debris could ruin the pump. To find a licensed well contractor check the Licensed Well and Boring Contractor Directory.
  • If floodwater reached your well, have a licensed well contractor disinfect your well – or complete the disinfection yourself – even if you don’t think the floodwater entered the well. Detailed instructions are available at Disinfecting Flooded Private Water Wells.
  • After you or the licensed well contractor disinfects your well and pumps out the chlorine solution, contact your county health department or a laboratory accredited by MDH about how to get your well water tested for coliform bacteria. They will provide instructions on how to submit a water sample for testing. Accredited Labs in Minnesota Accepting Samples from Private Well Owners (PDF).    
    • If your well water test comes back positive for coliform bacteria, repeat the disinfection and testing process. You may need to disinfect and test your well several times before your well is free of bacterial contamination.
    • Do not use the water from your well until the lab has informed you that it is safe and free of bacterial contamination.

If floodwater came within 50 feet of your well – but did not reach the well – MDH recommends that you have your well water tested for coliform bacteria as a precaution. You do not need to disinfect your well before having it tested. If the test comes back positive for bacteria, however, the well needs to be disinfected.

For more information, please contact the Well Management Section at MDH at [email protected] or 651-201-4600 or 800-383-9808 or visit the Natural Disasters and Private Wells page on the MDH website.  

-MDH- 

Media inquiries:
Andrea Ahneman  
MDH Communications 
651-201-5195 
[email protected]

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