Stay healthy and safe during a flood

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Drinking Water Safety 

Floodwater can contaminate well water with livestock waste, human sewage, and other contaminants that lead to illness when used for drinking, bathing, and other personal hygiene. 

If your drinking water comes from a public water system, contact them if you’re unsure if it’s safe to drink. You can find contact information on your water bill.

If your drinking water comes from a well that has been covered or surrounded by floodwaters, your water can be made safe to drink by boiling, using disinfectants, or filtering. The treatments described below work only to remove bacteria or viruses from water.

  • If you think your water is unsafe because of chemicals, oils, poisonous substances, sewage, or other contaminants, do not drink the water.
  • Don't drink water that is dark-colored, has an odor or contains solid materials.
  • If you can’t treat your water, use bottled water for drinking, food preparation, and other activities.


  • Boil water at a rolling boil for one minute, and then let it cool before using.
  • Most chemicals will not be removed by boiling.
  • Cloudy water should be filtered before boiling. Filter cloudy water using coffee filters, paper towels, cheesecloth or a cotton plug in a funnel.


If boiling is not possible, you often can make water safe to drink by using a disinfectant, like unscented household chlorine bleach. This method will kill most viruses and bacteria. Follow instructions for disinfecting your water carefully.

  • Treat water by adding liquid household bleach, such as Clorox or Purex.
  • Household bleach is typically between 5.25 percent and 8.25 percent chlorine. Read the label.
  • Avoid using bleaches that contain perfumes, dyes and other additives. Be sure to read the label.
  • Cloudy water should be filtered before adding bleach.
  • Place the water in a clean container. Add 8 drops or a little less than 1/8 of a teaspoon of 5%-9% unscented household bleach to 1 gallon water. For cloudy tap water, use 16 drops or ¼ teaspoon. You can get more detailed instructions on disinfecting your water from the CDC.
  • Mix thoroughly and let stand for at least 30-60 minutes before drinking.


Many portable water filters can remove disease-causing parasites from drinking water. Filters don’t remove bacteria or viruses. If you are choosing a portable water filter:

  • Try to pick one that has a filter pore size small enough to remove parasites (such as Giardia and Cryptosporidium). Most portable water filters do not remove bacteria or viruses.
  • Carefully read and follow the manufacturer’s instructions for the water filter you intend to use.
  • After filtering, add a disinfectant such as iodine, chlorine, or chlorine dioxide to the filtered water to kill any viruses and remaining bacteria.

Well Safety and Testing

If your well is affected by flooding, follow these steps to have it tested and made safe for drinking again.

  • When there is standing water, stay away from the well pump and turn off the electricity to avoid electric shock.
  • Seek a qualified well contractor or pump installer to assist with the following:
    • Clean, dry, and re-establish electrical service to the pump.
    • Disinfect and flush the well to remove any contamination that entered during the flood.
    • Perform any other necessary maintenance so that your well pump can return to service. Too much sediment in water can cause pump damage or failure, so we recommend you use professional contractors to assess and fix your pump.
  • After the pump is turned back on, pump the well until the water runs clear to rid the well of flood water.
  • If your water is still murky, you should have it tested before drinking. View this short list of certified water testing labs in Whatcom County, or search for a certified lab from other locations in Washington State. For additional well questions, you may want to contact a licensed well driller.

If you wish to disinfect your well yourself, follow these well disinfection instructions from the Washington State Department of Health.

Still have questions?

  • Call Whatcom County Health Department at 360-778-6000 to talk to a drinking water public health specialist.

Additional Resources

Returning to a location that was flooded:

There are many health risks to consider when returning to a location that’s been flooded. Risks to health and safety can include but are not limited to, such things as spoiled food, contaminated water, mold, and sewage.

Do not attempt to drive on roads that have been closed. Follow, and adhere to,Road with shoulder missing from flood damage road closure and safety signage. There may be road damage that is not visible.  

For information and tips on how to stay healthy and safe around flood water see the following resources: