The City of Toronto ensures that residents, businesses and visitors have access to clean, safe drinking water. This is done through a complex water treatment process and continuous testing so that water always meets or exceeds the Safe Drinking Water Act set by the Ministry of the Environment, Conservation and Parks (MECP).

Toronto’s tap water is continuously tested, monitored and analyzed to ensure it meets the strict standards of Toronto Public Health, the Province of Ontario and Government of Canada.

Toronto Water’s accredited lab:

  • tests drinking water every six hours (over 6,000 times a year)
  • conducts more than 20,000 tests at the water treatment plants annually
  • conducts 15,000 bacteriological tests on samples collected from the water distribution system annually

See the most recent drinking water quality and system reports submitted to the Ministry of the Environment, Conservation and Parks.

Each day, the City of Toronto treats more than 1 billion litres of safe drinking water at four water treatment plants, which operate 24 hours a day, seven days a week.

How treatment works

  • Water is collected from Lake Ontario through intake pipes deep below the lake and one to five kilometres away from shore.
  • Lake water passes through screens to remove large debris and then through filters to remove additional impurities. Water is disinfected by using either chlorine or ozone.
  • Alum or Poly Aluminum Chloride is added to the water to form a jelly-like substance that joins larger particles called floc, and goes through additional filtration.
  • The water travels though settling basins so larger particles settle to the bottom. The clear water at the top proceeds to filters containing gravel, sand and carbon to remove suspended impurities and bacteria.
  • Before water is pumped for distribution to homes and businesses, the following is added:
    • chlorine to destroy bacteria, algae and viruses
    • fluoride to help prevent tooth decay
    • ammonia to ensure chlorine levels remain consistent as water travels through the distribution system
    • phosphoric acid, which is used for corrosion control to help create a barrier between residential lead pipes and drinking water

Supply, storage and distribution

To ensure an uninterrupted water supply, there is a computerized process control system overseen by Toronto Water staff. The aim is to distribute superior quality water in a reliable, cost-effective and environmentally sound manner. Staff monitor:

To ensure adequate water pressure and supply, Toronto is split into six pressure zones and subdivided into 13 pressure districts, which are continuously monitored and adjusted based on demand. Additional water is stored in tanks and reservoirs, which helps maintain pressure and enough supply during peak periods and emergencies such as fires, watermain breaks and power outages.

Drinking water system & financial reports

See the most recent reports submitted to the Ministry of the Environment, Conservation and Parks regarding the operations, capital and operating budgets of the drinking water system.

Cloudy water

  • Water that looks cloudy is safe to drink and use, and is normally temporary
  • The cloudy appearance is normally from air bubbles in the water that should disappear within a few minutes. Air bubbles in the water can occur for the following reasons:
    • when different temperatures of water enter the plumbing system
    • when the water has been turned off during construction
    • with valve changes in the distribution system (a valve is a device that regulates, directs and controls the flow of safe drinking water in watermains)
  • To reduce the cloudy appearance:
    • run a cold water tap to allow the air to escape
    • pour some cold water into a glass. The air bubbles will rise to the surface and clear up within a few minutes. If the water is still cloudy or sediment appears, please contact 311 to initiate a water quality service request.


  • Chlorine is used in the drinking water process to control bacteria, algae and viruses.
  • The range of chlorine used is set by the Provincial Safe Drinking Water Act and is continuously monitored by the City to ensure the water is safe to drink.
  • If you are sensitive to chlorine taste and odours, fill a pitcher with water and let it stand overnight in the refrigerator.


  • Fluoride is added to Toronto’s drinking water to reduce the risk of tooth decay.
  • Fluoride levels in Toronto’s drinking water are regulated in Ontario under the Safe Drinking Water Act administered by the Ministry of the Environment, Conservation and Parks.
  • Learn more about fluoride from Toronto Public Health.

Discoloured tap water

  • Discoloured or rusty tap water can be caused by a number of different factors.
  • If only one tap is affected, this indicates a private plumbing issue. You may wish to contact a plumber.
  • If all taps are affected, this may be a result of plumbing work on your property, construction on a watermain in the area, or nearby fire hydrant use. Get tips on how to resolve the issue.

Earthy or musty smell/taste

  • Earthy, musty smell and/or taste can occur in late summer or early fall and can be the result of naturally-occurring algae and high water temperatures in Lake Ontario.
  • The water remains safe to drink during these events.
  • Taste and odour can also be a result of a private plumbing issue. Learn more about potential causes and what to do.

Lead and drinking water