Drinking Water Disinfection

How to Disinfect Your Water System

Use a chlorine bleach solution to disinfect your water supply after a flood, after construction or repair work (including replacing the pump), or when a water test result shows contamination with bacteria.


 Steps to Disinfection:

  1. Before you begin, disconnect, detour around, or remove any water treatment devices – such as carbon filters, water softeners or reverse osmosis units.

  2. Carefully and slowly pour 1 gallon of unscented regular household chlorine laundry bleach for every 525 gallons of water into your dug or drilled well. This means using 1 gallon of bleach for every 10 feet of 36-inch diameter dug well or every 350 feet of 6-inch diameter drilled well.

  3. If possible, run water through a garden hose back into the well for 10 to 15 minutes to help mix the chlorine with the well water, and to wash down the inside surfaces of the well.

  4. If possible, scrub the inside of the casing of a dug well or spring with a clean brush and a strong chlorine solution. (Mix one part household laundry bleach to four parts water.) Be sure to use rubber gloves, skin and eye protection.

  5. Recap the well. Go into your home and turn on one faucet at a time throughout the house. Run the water until you smell a strong chlorine odor, then turn the faucet off.

  6. It takes time for chlorine to disinfect, so it’s important to keep the chlorinated water in your system for 12 hours. After 12 hours, connect a hose to an outside tap, and begin to drain the chlorinated water from the well into to a safe outdoor location such as a graveled driveway or into a brushy area.

    • Do not drain chlorinated water onto a lawn or garden.
    • Do not let chlorinated water to reach a river, stream, pond or lake   because chlorine can kill fish.

  7. Run the water through the hose at less than full flow, or turn off the hose every so often so you don’t run your well dry. Continue flushing through a hose or home faucets until the strong odor of chlorine gets weaker or is gone.

    Sometimes the chlorine odor will stay for three to five days. Using household water in a normal fashion will help flush out the remaining bleach.

    • Some people with sensitive skin or eyes will want to bathe or   shower elsewhere. This will vary depending on the well.

  8. Collect water for total Coliform/E. coli testing (KIT A) two to three days after the chlorine odor is gone. Continue to either boil water or get drinking water from a known safe source until test results show your water is safe again.

Return to Top