Well Disinfection

Well Disinfection

Well Disinfection is the process of using chlorine or another disinfectant, in a well to kill potentially dangerous microorganisms. These microorganisms may be present if your well have been contaminated. If your well is new, repaired, or has had the sanitary seal removed, it should be considered contaminated. Contamination of well water happens through exposure and contact to soil and most surfaces, thus construction, repair and maintenance to a well must be followed by a complete and proper disinfection.

well disinfection of bacteria

A water sample analysis that tests for coliform bacteria may be performed before chlorination to detect its presence. However, you should always test the water no earlier than 24 hours after completing the well disinfection process. This ensures that no coliform bacteria is present in the water and it is safe to use.

Why Disinfect?

  • When coliform bacteria are present in the water
  • After flooding of the well
  • After plumbing installation, example: water treatment, sinks, filters
  • After casing or pump repairs
  • When water taste or odour changes, example from iron or sulfur reducing bacteria
  • As part of annual maintenance
  • During startup of seasonal wells.

Do you need your well disinfected? Contact us today to set up your service call with one of our skilled technicians. Call us toll-free at: 1-800-900-2220 or 604-534-1115.

Would you like to disinfect your own well? Follow our guide to Well Disinfection.

Guidelines for Well Disinfection Using Sodium Hypochlorite

  1. Store enough water for 24 hours of use.
  2. Measure the diameter of the well and calculate the volume of chlorine bleach (5.25% active chlorine- household bleach using Table 1 below).
  3. Remove the well cap.
  4. Test the pH. Ideally, the pH should be 7 or less. If it is above, add one litre of vinegar or citric acid to the well. Re-test the pH.
  5. *********     WARNING!!!   pH should not be adjusted below 5.5 pH otherwise chlorine gas will form. *******
  6. Mix the bleach in a 5 gallon pail of water. Pour the bleach solution into the well. If the well has a sanitary seal, pour or siphon the bleach solution through the well vent.
  7. Run a garden hose into the well to circulate the bleach until the presence of chlorine is detected.
  8. Rinse off well cap with chlorinated water and re-fasten to well head.
  9. Run water at each individual tap until a strong chlorine odour is detected, including outside and hot water taps.
  10. Let the system sit idle for 24 hours. No water should be used during this 24-hour period, except for toilet flushing.
  11. Caution: Bleach solution is strong enough to burn. Keep away from skin, eyes, and children.
  12. Open all taps (hot and cold) and let run until chlorine odour can no longer be detected.
  13. Wait 24 hours before catching a sample for a bacteria test.

Table 1
Liquid Chlorine (Sodium Hypochlorite)
Required to Produce 50 mg/L of Solution In 100' of Water

Well Diameter (inches) Ounces of 5.25% Bleach to Produce 50 mg/L of Solution in 100' of Water Litres of 5.25% Bleach to Produce 50 mg/L of Solution in 100'
4 9 0.3
6 20 0.6
8 34 1.0
10 56 1.7
12 80 2.4
16 128 3.8
20 214 6.4
24 298 8.7


Or disinfect your well the easy way !!!!  Use our product " Steriline" 

  • 200 times more powerful then chlorine.
  • No need to adjust pH
  • Specialy formulated to disinfect for coliform bacteria
  • Easy to use instruction on the container.   
  • Steriline Brochure


Well Disinfection Tips

  • Disinfection or sanitization of any well will only kill the bacteria present in the well or on the pumping equipment.
  • Every well should be sanitized after construction.
  • Each time equipment is removed from a well and re-installed, the well should be sanitized to avoid bacterial contamination.
  • The source of bacterial contamination should be identified and removed wherever possible.
  • The quantity of chlorine used to sanitize and disinfect a well must produce 50 mg/L (ppm) of chlorine solution when mixed with the total volume of water.
  • Faucets on fixtures discharging to a septic tank system should be temporarily diverted to an outside discharge point to avoid having the chlorine solution enter the septic system.
  • Bypass carbon filters, RO membranes, and other water treatment equipment that could be damaged if it comes into contact with chlorine. Sanitize these pieces of equipment separately.
  • pH adjustment is critical for proper well disinfection.
  • A residual chlorine of 50 mg/L is necessary for disinfection. Figures given in Table 1 are for 50 mg/L in 100' of water. A solution of 50 mg/L should be sufficient to oxidize any iron or manganese present and sanitize the water system.

Do you need your well chlorinated? Contact us today to set up your service call with one of our skilled technicians. Call us toll-free at: 1-800-900-2220 or 604-534-1115.