How to Disinfect Your Well

Chemical disinfection or chlorination of a water supply is suggested when a well has been found to be contaminated by bacteria. New wells and repaired wells, and any associated plumbing, should be disinfected before being put into service. The routine annual disinfection of a well will also help to control "nuisance" levels of bacteria that may build up over time.

Procedure to follow:

1. Mix one litre of liquid laundry bleach (5-9% Hypochlorite) with approximately 45.5 litres (10 gallons) of water. Pour the solution into the well between the drop pipes and the outer casing. This may be done by pouring or siphoning through the air vent, or by removing the well seal or cap. 
2. Go to each faucet in the house (hot and cold) one at a time and run the water just long enough to smell the chlorine at the tap, then turn the faucet off. Go to the next faucet and repeat the process. 
3. Repeat step #1, but this time do not open the taps and run the water. Replace the well cap or seal and let the system sit idle for eight to 12 hours, preferably overnight. Minimize water use during this period. 
4. After the chlorinated water has been sitting in the system for a minimum of eight to 12 hours, the water should be run to flush the chlorine out of the system. It is recommended that water be run off from a hose on an outside tap to avoid overloading the septic system. When there is no longer a chlorine odour at the outside tap, run all inside faucets until the chlorine odour has disappeared. 
5. Wait 48 hours after the disinfection procedure is completed before resampling the well. It is recommended that two consecutive samples with no bacteria present be obtained before using the water for human consumption. 

Chlorine should always be used in well-ventilated places because breathing the fumes is dangerous. Remember, disinfection of an improperly located or constructed well and/or water supply will not ensure good quality drinking water. Disinfection of the well and water system is considered to be only a temporary solution. If bacteria problems persist after disinfection, permanent corrective measures should be considered such as well reconstruction or ultraviolet light treatment.

Who can I contact for more information?

Paul Baker (Safety Standards Officer)
4th Floor, Jones Building
11 Kent Street
Charlottetown, PEI C1A 7N8
Telephone: (902) 368-5062
Fax: (902) 368-5830
Email: psbaker@gov.pe.ca