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Environmental Health Division
Flood Precautions For Private Water Wells
The Minnesota Department of Health (MDH) is advising well owners that private water wells contaminated with flood water can pose a health risk. MDH recommends that well owners take precautions before possible flooding, and that they take corrective actions should a well be flooded.
MDH recommends that well owners take the following steps if they think their well may become flooded:
- Store a supply of clean water before taking your well out of service.
- Disconnect the power supply for your well. If you need help, consult with a licensed well contractor or pump installer.
- If you have time, have a licensed well contractor install a watertight cap or cover on your well – temporarily replacing the regular vented well cap. If your well has been flooded multiple times, you may want to discuss permanently extending the casing of your well above the flood level with a licensed well contractor.
- If you don't have time to hire a well contractor install a watertight seal, clean off the outside of the well casing and cover the top of the well with a heavy-duty trash bag or some other form of heavy plastic sheeting. Secure the plastic covering with electrical tape or some other type of waterproof tape, strapping material, or wire. Do not use duct tape – it won’t hold under flooding conditions. Wrapping the well with plastic won’t eliminate the need for disinfection and testing, but it will keep debris and sediment out of the well, and make the post-flood clean up go more smoothly.
- Be prepared to have your well disinfected and tested after the flood waters recede.
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Flood water reached well
If flood water reached your well or covered the top of your well casing, assume your well is contaminated. Water from your well should not be used for drinking, cooking, or brushing your teeth until the flood water recedes and the following steps have been completed:
- If flood water covered your well or may have entered your well directly, have a licensed well contractor inspect the well and if necessary clean out any sediment or debris that may have entered your well. Using your well pump to do this could ruin the pump. Have the licensed well contractor disinfect your well. Go to Licensed Well and Boring Contractor Directory.
- If flood water reached your well but you are confident that flood water did not enter the well, have a licensed well contractor disinfect your well or complete the disinfection yourself. Disinfect your well using a chlorine solution. Detailed instructions are available at Disinfecting Flooded Private Water Wells.
- After disinfecting the well and pumping out the chlorine solution, contact a MDH-certified laboratory for testing a water sample. Tell them you need to have your well tested for coliform bacteria. They will tell you what you need to do, and provide a bottle for the sample. To find a laboratory, contact your local health department or go to the MDH Accredited Laboratories.
- It may be necessary to repeat the disinfection and testing process several times to ensure that your well is free of bacterial contamination. Disinfect your well yourself or contact a licensed well contractor to complete this for you. Disinfect your well using a chlorine solution before having it retested.
- Don’t use the water from your well until the lab has informed you that it is safe, and free of bacterial contamination.
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Flood water within 50 feet of well
If flood water came within 50 feet of your well – but did not reach the well – you may still want to have your water tested as a precaution. You do not need to disinfect your well before having it tested.
For more information about well safety and protecting your health during a flood see:
- Bacterial Safety of Well Water
- Disinfecting Flooded Private Water Wells
- Emergency Preparedness, Response, and Recovery
- Floods: Protecting Your Health
During an Emergency
Print Information Sheet
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