Corrosion Control

Since 2014, the City has been adding phosphate to the drinking water treatment process. Phosphate forms a protective coating inside all pipes and household plumbing fixtures, which helps to reduce the potential for lead to enter tap water.

Corrosion control is mandated and approved by the Ministry of the Environment, Conservation and Parks (MECP) under the Safe Drinking Water Act.

Toronto’s Corrosion Control Plan was adopted by City Council, and is supported and endorsed by Toronto Public Health as a safe way to reduce the amount of lead in tap water and the associated health risks.

About the Plan

  • The City began to add phosphate to the water treatment process at its four plants in 2014.
  • It took approximately two years for a protective coating to form inside all pipes.
  • The City is continuously evaluating the effectiveness of corrosion control and is adjusting the phosphate dose accordingly.
  • Ongoing lab results from homes with suspected lead pipes show that lead levels are decreasing.
  • Find out more by viewing the results for the Ontario Regulated Lead Testing Program.

About Phosphate and Public Health

  • Phosphates are naturally found in many foods, including milk, beef and nuts, and are required for normal cellular function.
  • The phosphate being used at the City’s water treatment plants is a food grade additive derived from a natural source of mineral rock.
  • It represents less than 1% of what a person typically consumes each day.
  • It has no impact on the taste or odour of drinking water.

Annual Report – Lead in Drinking Water Mitigation

Read the latest Annual Lead Mitigation Report on the City of Toronto’s Lead in Drinking Water Mitigation Strategy.

If you have a cooling tower

The addition of phosphate in source water may change the type and amount of precipitate that deposits and insulates commercial heat exchangers. As a result, companies may need to decrease their number of operating cycles, or alter their chemical treatment. It is recommended that companies contact their heating and cooling supplier or process consultant to discuss whether slight modifications are needed.

If you have a steam boiler

The impact of phosphate on boilers should be minimal. Many customers already add phosphate to precipitate calcium and/or as a tracer in their boiler system. The addition of phosphate to the drinking water treatment process will increase phosphate levels in the boiler feed water, and ultimately, in the boiler water. For this reason, customers already adding phosphate to precipitate calcium may benefit from the implementation of Corrosion Control. These customers should measure their background phosphate levels and adjust their own phosphate dosage accordingly. Customers currently using phosphate as a tracer may need to find an alternative.

If you use water to create products

The majority of companies that additionally treat the City’s drinking water for use as a product ingredient will not require adjustments. However, it is recommended that companies contact their process consultants to confirm.

Phosphate and tap water pH

The addition of phosphate will decrease the pH of the water by less than 0.1 pH units.