Chlorine plays an important role, as a disinfectant, to ensure water is free of bacteria, algae and virus. Chlorine must be present at all times in the water, within the Ministry of the Environment, Conservation and Parks regulatory requirements, to maintain the quality and safety of water as it leaves the treatment plants and travels through the distribution system. Some people are more sensitive to changes in the drinking water treatment process and may notice changes in the taste and odour of their tap water. This may be attributed to chlorine. The City of Toronto adjusts the amount of chlorine in the drinking water at various times during the year to ensure chlorine levels in the outer limits of the distribution system remain within regulatory limits.

The Safe Drinking Water Act set by the Ministry of the Environment, Conservation and Parks states that chlorine in drinking water must optimally be between 1 and 3 mg/litre.

  • The average amount of chlorine in Toronto's drinking water leaving the treatment plants ranges between 1.5 and 2.0 mg per litre. Chlorine levels are usually lower in the far ends of the distribution system.
  • There are several factors that can influence the amount of chlorine that may be needed during the drinking water treatment process including water consumption, water temperature, and the conditions in Lake Ontario.
  • The City of Toronto continuously monitors chlorine levels at the plant and in the distribution system, and adjusts its water treatment processes accordingly.
  • Toronto water is tested over 6,000 times a year to ensure it is safe to drink. The City of Toronto tests water every six hours (4 times a day). Toronto's drinking water is safe to drink.

In order to alleviate chlorine taste and odour concerns, residents can fill a pitcher with water and let it stand overnight in the refrigerator to help dissipate some of the chlorine.

You can obtain information on water filtration by visiting the Toronto Water website.