Heavy rains during recent weeks flooded and contaminated thousands of private water wells in the Northeast, warns Brian Swistock, Penn State University Extension water-quality specialist. Those wells should be disinfected.
In addition to seeing flood water (or standing water) around your wells or springs, you may notice increased sediment in well or cistern water. Even after this goes away, bacteria still may have contaminated the water supply. The sediment is a clue, he says.
A simple coliform bacteria test from a water-testing lab can determine if the water supply is safe to use or if disinfection is needed. Your county Extension office can tell you where to get them.
Well disinfecting procedures
Swistock urges following these steps. You'll need at least a gallon of non-scented household liquid bleach, rubber gloves, eye protection, old clothes and a funnel.
If the water is muddy or cloudy, run the water from an outside spigot with a hose attached until the water becomes clear and free of sediment.
Determine what type of well you have and how to pour the bleach into the well. Some have a sanitary seal with either an air vent or a plug that can be removed. If it is a bored or dug well, the entire cover can be lifted off.
Mix a gallon of bleach with a few gallons of water. Using a funnel (if needed), carefully pour the bleach mixture into the well casing.
After adding the bleach, run water from an outside hose into the well casing until you smell chlorine coming from the hose. Then turn off the hose. If chlorine odor never develops at the faucet, you may need to add more bleach to the well.
If you have a water treatment system, switch it to bypass. Then turn on all cold water faucets, inside and outside of the house, until the chlorine odor is detected in each faucet. Then shut them off.
Wait six to 24 hours before turning the faucets back on. Do not use this water for drinking, cooking, bathing or washing during that time period.
Once the waiting period is up, turn on an outside spigot with hose attached and run the water into a safe area where it won't disturb plants, lakes, streams or septic tanks. Run the water until there's no chlorine odor.
Avoid using the water for drinking until a bacteria test confirms that the disinfection did the job. Have the water tested, again, for bacteria seven to 10 days after disinfection.
You can download a free Penn State fact sheet, "Shock Chlorination of Wells and Springs," at http://www.age.psu.edu/extension/factsheets/f/F%20140.pdf.