Press Release

BALTIMORE, MD (September 22, 2003) – As flood waters recede and power is restored following Hurricane Isabel, Maryland Department of Environment (MDE) Acting Secretary Kendl P. Philbrick recommends that homeowners utilizing wells that were flooded, disinfect their systems prior to consumption--including drinking, cooking, brushing teeth or preparing food. In the interim residents are urged to use bottled water or obtain water from emergency response distribution centers.

“If you have an individual well and know, or suspect that flood waters have entered your well, it is potentially contaminated,” Philbrick said. “People who obtain their water from an individual well should disinfect the well and distribution system if floodwaters reached and entered the well casing. In order to safeguard public health and personal well being, it is best to use a safe source until disinfection is complete and testing shows the water to be safe. If you know that the flood waters were contaminated with petroleum products (oil sheens or displaced storage tanks in the area), we advise that the well be tested for petroleum contamination prior to use.”

Residents should contact their local health department regarding specific questions they may have about testing and well safety. If residents do not have access to bottled water or an alternative safe source, their well water should be boiled for one full minute in a clean container. Evidence of contamination may be cloudy or dirty water. Prior to boiling, the well should be run (2 hours for every 100 feet of well depth for a six inch well) to remove as much of the contaminated water from the well as possible. The one-minute boil time begins after the water has been brought to a rolling boil. Allow water to cool before using. Boiling is the most effective method of disinfecting water, particularly for people who are severely immunocompromised (infected with HIV/AIDS, cancer and transplant patients taking immunosuppressive drugs, or people born with a weakened immune system) and for infants and elderly who wish to take extra precautions.

The well should be run until the water is clear before beginning disinfection. To disinfect a well, mix two quarts of liquid chlorine laundry bleach with 10 gallons of water and pour the contents down the well. Replace the well cover and turn on water taps until there is an odor of chlorine. Once a chlorine odor is detected, immediately turn the tap off. After allowing the chlorinated water to stand in the piping and the well for at least eight hours, open all taps and spigots and flush out the chlorine. Keep flushing until the chlorine odor has disappeared.

Contact your local health department to determine if they are available to assist in sampling, following the disinfection procedure. You may also wish to contact a Maryland-certified private laboratory to analyze a water sample for bacteriological quality. Typical fees range from $50 to $75. A complete listing of certified laboratories throughout the state can be obtained on the Maryland Department of Health and Mental Hygiene’s website at: or call MDE’s Water Supply Program at (410) 537-3702. (Note: Testing may not be needed if only the power was lost to the pump/motor without the well casing also being flooded.) Continue to use an alternative source or boil all drinking water until such time as a laboratory reports that sample results indicate the water is safe.

If unable to boil water due to a power outage, the following other methods may be considered.

  • If the water is clear, mix 1/8 teaspoon of unscented, liquid chlorine laundry bleach with one gallon of water and let it stand for at least 30 minutes prior to consumption. If the water is cloudy or colored, use ¼ teaspoon per gallon of water. Be sure to mix thoroughly. If the treated water has too strong a chlorine taste, it can be made more palatable by allowing the water to stand exposed to the air for a few hours or by pouring it from one clean container to another several times.
  • If the water is clear, mix five drops of 2% United States Pharmacopeia (USP) tincture of iodine solution (common household tincture of iodine from the medicine cabinet or first aid package) to each quart of clear water and let it stand for at least 30 minutes prior to consumption. If the water is cloudy or colored, use 10 drops to each quart of water. A flat taste can be eliminated from water by shaking it in a bottle or pouring it from one container to another.

For further questions regarding individual wells, contact the MDE’s On-Site System Division at (410) 537-3778. Questions regarding public water systems and certified laboratories can be referred to MDE’s Water Supply Program at (410) 537-3702. For questions regarding petroleum contamination and spills please contact MDE’s Oil Control Program at (410) 537-3442. MDE’s emergency response number to report any type of pollution event is 1-866-MDE-GOTO.