Skip Navigation

Disinfecting Your Well

Disinfecting your well eliminates bacterial contamination after repairs, maintenance, or an unfavourable water sample result. Learn the proper steps to disinfecting your well.

Well disinfection is a temporary method of disinfection used to remove bacterial contamination. It is important to identify and correct the source of contamination before disinfecting your well. This will ensure the continued safety of your water supply.

You should disinfect your well after:

  • Construction of your well
  • Repairs to your well
  • Maintenance of your well
  • Well water has not been used for some time
  • Obtaining a contaminated water sample result
  • Flooding has occured

Well Disinfection Procedure

After you disinfect your well, be sure to test your drinking water for harmful bacteria such as coliforms and E.Coli. Avoid drinking the water until you receive three sample results, taken 1-3 weeks apart, indicating the water is safe to drink.


Follow these steps to disinfect your well or print a hard copy (PDF file):

  1. Measure the well diameter.
  2. Calculate the depth of water in the well by subtracting the distance from ground level to the water level in the well.
  3. Using the table below, measure the amount of bleach (5.25% solution) needed. Follow safety precautions on the product label.
  4. Mix the chlorine in a bucket with water. Pour the mixture down the inner wall of your well casing. If possible, mix the solution in the well. · Mix the solution by attaching a hose to a tap and running water from the well through the hose and back into the well. Agitate the well water while avoiding the suspension of sediment from the bottom of the well into the water columns.
  5. Remove any carbon filters on the system to ensure the chlorine reaches the pipes beyond the filter. Replace all filters after disinfection to avoid reintroducing bacteria into the system.
  6. Run water at every internal and external faucet until you smell chlorine. Turn off faucets.
  7. Drain the hot water tank and fill with chlorinated water.
  8. Back-flush the water softener and all water filters (except carbon filters).
  9. Leave the chlorinated water in the system overnight, or at least 12 hours.
  10. Remove chlorinated water from the well by attaching a hose to an outside tap and running the water until you can no longer smell chlorine. Make sure to direct waste water away from the septic system. Run all indoor faucets until you no longer smell chlorine.
  11. Test your well water 3-5 days after disinfection. Do not drink the water until you receive 3 results, taken 1-3 weeks apart, indicating the water is safe to drink.

Volume of Bleach to Add per 3 meters (10 feet) of Water in Well

Casing Diameter

Volume of Unscented Bleach (5.25% Solution)

50 mm


6 ml

100 mm


30 ml

150 mm


60 ml

200 mm


100 ml

250 mm


200 ml

300 mm


250 ml

400 mm


400 ml

500 mm


650 ml

600 mm


900 ml

900 mm


2000 ml (2 L)

1200 mm


3600 ml (3.6 L)