Health officials urging well users to protect private wells from potential flood contamination

Published 8:32 pm Wednesday, March 20, 2019

With the risk of flooding increasing in many parts of the state, Minnesota health officials urge private well users to prepare for the possibility that their wells might flood. Taking preventive action now may save well users more trouble down the road.

Wells contaminated with floodwater pose a health risk, but the impact floodwaters have on wells and water quality are often not as visible as other flood damage. With that in mind, the Minnesota Department of Health offers well users the following recommendations:

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.

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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 will help reduce the amount of water and debris that could enter your well, making clean up easier.

If floodwater reaches your well, assume your well is contaminated. Water from a contaminated well should not be used for drinking, cooking, or brushing your teeth until the floodwater recedes and the following steps have been completed:

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. Using your well pump to remove sediment or debris could ruin the pump. A directory of licensed well contractors is available on the MDH website at Licensed Well and Boring Contractor Directory.

If floodwater reached your well but you are confident that floodwater did not enter the well, have a licensed well contractor disinfect your well or complete the disinfection yourself. Detailed instructions are available on the MDH website 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 to get your well tested. Tell them you need to have your well water tested for coliform bacteria. They will provide sampling instructions. You can find accredited labs on the MDH website under accredited labs in Minnesota accepting samples from private well owners.

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 having your well water tested for coliform bacteria as a precaution. You do not need to disinfect your well before having it tested. However, if the test comes back positive for bacteria, the well needs to be disinfected.

Well owners needing more information can contact the Well Management Section of MDH at 651-201-4600 or