How To Disinfect Wells After Flooding

UPDATED: 1:51 pm EDT April 17, 2007

State officials recommend that residents disinfect private wells after flood conditions.

According to the state Department of Public Health, private wells that flood should be considered contaminated and need to be disinfected.

The following information is from the DPH:

Water should be pumped away or allowed to recede around the well before the well is disinfected. Homeowners with dug wells should expose their wells and clean the well of possible debris that may have been swept in before carrying out disinfection.

A licensed electrician should evaluate electrical panel and/or connections that have been submerged due to flooding. In order to ensure that water is free from bacteriological contaminants, the well should be sampled after it has been disinfected and the disinfectant allowed to dissipate.

A certified laboratory should conduct all testing, and provide all containers used to collect samples. A list of certified laboratories may be found at the web address listed under Additional Resources or by calling the Environmental Laboratory Certification Program by dialing 860-509-7389.

If there are other suspected contaminants or other concerns, DPH suggests that residents notify their local health department or district.

The following is a procedure for disinfecting a private well:

Use non-scented chlorine bleach with a bleach solution equal to or greater than 5.25% solution. If bleach less than 5.25% is only available, increase amount of bleach accordingly.
Remove all membranes, filters, cartridges, and charcoal filters from water treatment devices after the chlorination process is completed
Clean the well of any debris. Do not disinfect the well until floodwaters have receded.
Run water until it is relatively clear.
Turn off and drain storage tank and hot water tank so that chlorinated water will also enter the tank.
Mix a batch of chlorinated water in a 5-gallon pail and use this mixture to clean along the top of the well. One half cup to 1 cup of bleach (5.25%) in 5 gallons of water is a relatively good concentration.
The chlorine batch in the 5-gallon bucket should be poured into the well so that it swirls around the interior casing.
Re-cap the well and then proceed to open each hot and cold faucet (inside and outside the house) until a distinct chlorine odor is observed. Then close each faucet.
If you do not detect a strong chlorine odor, add more bleach and repeat the process.
Backwash water softeners, sand filters and iron removal filters with chlorinated water.
Allow the chlorinated water to remain in the water system for at least 6 hours and preferably overnight.
Open all faucets individually and run the water until there is no chlorine smell – this process may take 15 minutes or more.
On outside faucets, make sure that chlorinated water is diverted from plants, shrubs. Chlorinated water will kill the vegetation.
If a resident is uncomfortable doing the disinfection process, a licensed plumber, pump installer or well driller should be contacted to perform the disinfection process.

Take Precautions For Mold

The DPH also urges residents to take precautionary measures to avoid indoor air quality problems associated with flooding. Moisture that enters buildings from leaks or flooding accelerates mold growth. Molds can cause disease, trigger allergic reactions and continue to damage materials long after the storm. Failure to control moisture and mold can present short and long-term health risks.

To protect against health risks associated with mold, the DPH recommends that residents do the following:

Remove standing water from your home or office.
Remove wet materials.
If mold growth has already occurred, carefully remove or clean the moldy material.
Consider using personal protective equipment when cleaning or removing mold -- gloves, goggles and an N-95 particle respirator (found at most local hardware stores). Check with a health-care provider before wearing a respirator. Do not use a respirator if you have heart disease or chronic lung disease such as asthma or emphysema.
Individuals with known mold allergies or asthma should not clean or remove moldy materials.
Remember to not mix cleaners and disinfectants, as hazardous chemical reactions may produce hazardous. Read and follow label instructions carefully. Open windows and doors to provide plenty of fresh air.

For more information about indoor air quality and mold growth, contact your local health department and you can visit the DPH Web site.

Additional resources recommended by the DPH: