How To Disinfect Your Well Water After A Flood

If your well becomes submerged due to flooding, it may have become contaminated with bacteria. The Department of Health recommends disinfecting the water in wells that have been submerged. If you notice a change in taste, odor, color or appearance, it is recommended that you use bottled water.

Follow these steps to disinfect (chlorinate) your well water.

  1. Prior to chlorination, draw off enough water for about 24 hours of household use not for drinking, but for flushing the toilet. Bypass any water conditioning equipment.
  2. Remove the well cap, and pour 1 gallon of bleach into the well. (NOTE: Dug wells require 2 gallons of bleach.)
  3. Connect a garden hose to an outside tap. Place the hose inside the well. Turn the water on at the outside tap, and allow the water to circulate for 2 hours. Turn the water off, remove the hose, and replace the well cap.
  4. Run water through each tap in the house. Immediately turn off the tap after detecting a strong chlorine odor or milky water. Allow the chlorinated water to remain in the plumbing system for at least 24 hours.
  5. Then, run the water from an outside tap through a garden hose until the chlorine odor has completely disappeared.
  6. Removal of chlorinated water from the well may take 2 to 3 days. Follow-up bacteriological testing is recommended by a state certified private laboratory. For a listing of state certified private laboratories, visit the Maryland Department of Health’s website.


Do not run the chlorinated water into your septic system, as it may overload its capacity. Do not use the heavily chlorinated water for bathing, laundering and washing sterling silver. If you have a water treatment system, contact your water conditioning company before reconnecting. Well chlorinations introduce high levels of chlorine that could damage your system.

For more information, contact:
Well Construction & Water Quality Program
Anne Arundel County Department of Health
3 Harry S. Truman Parkway
Annapolis, Maryland 21401