Courtesy Penn State University To disinfect a well aftering flooding, mix 1 gallon of bleach with about 3 gallons water and pour down the well casing.

As rural residents in the Northeast continue to recover from the effects of Hurricane Sandy, those who rely on private wells for water should make guarding against possible flood contamination a top priority. Whenever flooding occurs, well owners should disinfect their water supply before drinking water from them, according to Bryan Swistock, water resources extension associate at Penn State University.

“Hundreds, if not thousands, of water wells may have been flooded or affected by runoff from this storm,” Swistock says. “In addition to seeing flood water around their wells or springs, homeowners also might notice increased sediment in their water. Even after this goes away, bacteria still may contaminate the water supply.”

A simple coliform bacteria test from a water-testing lab can determine if your water supply is safe to use or if disinfection is needed.

“If residents suspect that their wells may be contaminated, they should contact their local or state health department for specific advice on disinfecting them,” Swistock says.

Local well drillers and contractors should also be contacted to inspect well components, and Swistock urges residents to follow the suggestions below, from the U.S. Environmental Protection Agency, for dealing with a flooded well:

• Inspect well and pump: If flood conditions are known to have occurred or are suspected at a well, the well and pump should be inspected. Swiftly moving flood water can carry large debris that could loosen well hardware, dislodge well-construction materials or distort the casing. Coarse sediment in the flood waters could erode pump components. If the well is not tightly capped, sediment and flood water could enter the well and contaminate it. Floods can also cause wells to collapse.
• Check electrical system: After flood waters have receded and the pump and electrical system have dried, have the wiring checked by a qualified electrician, well contractor or pump contractor before turning on the equipment. If the pump’s control box was submerged during the flood, all electrical components must be dry before electrical service can be restored. Get assistance from a well or pump contractor in turning on the pump.
• Monitor pump operation: All pumps and their electrical components can be damaged by sediment and floodwater. Clean the pump, including the valves and gears, of silt and sand. If pumps are not cleaned and lubricated properly, they can burn out. Get assistance from a well or pump contractor, who will be able to clean, repair and maintain different types of pumps.
• Disinfect wells: Before emergency disinfection, check the condition of the well. Make sure there is no exposed or damaged wiring. If you notice any damage, call a professional before the disinfection process. Materials needed include at least 1 gallon of unscented household liquid bleach, rubber gloves, eye protection, old clothes and a funnel.

To disinfect your well, follow these steps:

1. If the water is muddy or cloudy, use a hose to run the water from an outside spigot until the water becomes clear and free of sediment.
2. Determine the type of well you have and how to pour the bleach into the well. Some wells have a sanitary seal with either an air vent or a plug that can be removed. If it’s a bored or dug well, the entire cover can be lifted off to provide a space for pouring the bleach into the well.
3. Mix 1 gallon of bleach with a few gallons of water. Carefully pour the bleach mixture into the well casing, using a funnel if needed.
4. After the bleach has been added, run water from an outside hose into the well casing until you smell chlorine coming from the hose, then turn off the outside hose. If chlorine odor never develops at the faucet, you might need to add more bleach to the well.
5. Turn on all cold-water faucets inside and outside of the house, until the chlorine odor is detected in each faucet, then shut off all of them. If you have a water-treatment system, switch it to bypass before turning on the indoor faucets.
6. Wait six to 24 hours before turning the faucets back on. Caution: Do not use this water for drinking, cooking, bathing or washing during this time period—it contains high amounts of chlorine.
7. Once the waiting period is up, turn on an outside spigot with hose attached and run the water into a safe area where it will not disturb plants, lakes, streams or septic tanks. Run the water until there is no longer a chlorine odor. Turn the water off.

The system now should be disinfected, and you can use the water; however, the water should not be used for drinking until a bacteria test indicates that the disinfection procedure was effective. Have the water tested for bacteria seven to 10 days after disinfection.