Backflow Prevention Program

About the Backflow Prevention Program



Toronto Water delivers safe and clean drinking water through a network of water main’s and local distribution systems, known as the “waterworks”. In order to protect the public, the Water Supply By-law takes a proactive approach towards preventing the contamination of water in the waterworks. The Safe Drinking Water Act and regulations of the Ontario Ministry of the Environment (MOE) require the City of Toronto to provide safe drinking water to its residents.

The normal flow of water is from the public water supply system into private water systems; however, backflow (the reversal of flow) could occur as a result of either back-siphonage or back-pressure. Backflow can result in potential contamination of the water supply if sources of chemicals, pollutants, toxic substances, communicable bacteria and pathogens, or non-potable water, etc., enter into the public water supply system.

The Water Supply Bylaw (PDF) (Municipal Code, Chapter 851) was enacted on October 22, 2007 and is in effect as of January 1, 2008. The By-Law includes a program for backflow prevention to ensure the safety of Toronto’s drinking water. The program focuses on the isolation of the private water systems in certain premises from the waterworks, where the potential for backflow and contamination presents a risk to drinking water safety.

Building Permit is required for the installation of all premise isolation backflow preventers regardless of the size of the water service connection.

All installations of the premise isolation devices and all related items should be done in accordance with the Building Code, Canadian Standards Association (CSA) –B64 series standard, Municipal Code Chapter 851 and manufactures specifications. Before any installations, tests or surveys are conducted for the premise isolation backflow prevention program, the authorized person as per the authorized function list in Schedule 6 of the Bylaw (PDF), must submit a copy of all the required documentation to the backflow prevention program in order for the installation, test and survey to be recognized.

Back to the top


Responsibilities of the City of Toronto

The City implements a backflow prevention program to:

  • Administer and enforce a backflow prevention program to ensure compliance with the Water Supply By-law.
  • Require ICI and some multi-residential properties to identify backflow hazards where there is a potential for contamination of the drinking water system.
  • Ensure that certain Industrial, Commercial and Institutional (ICI) properties and some multi-residential properties install appropriate premise isolation backflow prevention devices (that is, at the connection to the waterworks, downstream of the water meter).
  • Ensure that owners applying for new water service connections implement any backflow prevention requirements specified in the By-law.
  • Provide assistance to affected property owners to help them understand and comply with the Backflow Prevention Program.

Back to the top


Responsibilities of the Owners of Industrial, Commercial and Institutional (ICI) and Multi-residential Properties

All ICI properties and multi-residential properties of 5 units or more, require a premise isolation backflow prevention device to be installed. All property owner's shall:

  • When required by the General Manager Toronto Water, conduct a backflow prevention survey to evaluate potential risks that may cause backflow to enter public water supply systems;
  • At the owner’s expense, install appropriate premise isolation backflow prevention devices to protect the public Waterworks against contamination. The devices shall be installed at the incoming water service connection downstream of the water meter. If necessary, any proposed alternate location must first be authorized by the General Manager Toronto Water. In all cases, the device must be readily accessible;
  • Hire an authorized person, as per the authorized function list in Schedule 6 of the Bylaw, to conduct a test after installation of the backflow prevention device and annually thereafter. Testing must also take place within 72 hours after the device is cleaned, repaired, replaced, serviced or overhauled;
  • Maintain records of backflow surveys and backflow prevention device tests and ensure tags are placed on all backflow prevention devices to identify information required under the By-law;
  • Submit backflow prevention device test reports annually to the City of Toronto and according to all other requirements specified in the Water Supply Bylaw;
  • Ensure all piping between the water meter and the premise isolation backflow prevention devices is clearly labelled “No Connections Permitted”;
  • Notify the City of any change in hazard level. This could be due to a change in building operations or activities, or any changes in  the service connection to the building or property;

Back to the top


Responsibilities of the Owners of Single Family Dwellings

While the installation of a backflow prevention device is not required for normal single family dwellings under the Water Supply By-law, an owner can take proactive steps to help protect the drinking water system:

  • Never place the end of a hose into places where contaminates can be siphoned back into the waterworks. Examples of sources of contamination include a bath tub or spa, laundry sink and pail, swimming pool, fish tank, floor drain, lawn irrigation, etc.
  • Leave at least a one inch (1") gap between the end of any water hose/faucet and the source of potential contamination.
  • If applicable and possible, install backflow control devices to protect from heating boiler, underground lawn irrigation system, etc.

For an owner of a single family dwelling is where an auxiliary water supply system, such as a well, is present. In that situation, the owner will be required to conduct an on-site assessment survey and install a premise isolation backflow prevention device.

For the owner of a single-family dwelling where there is an auxiliary water supply system, the owner will be required to conduct an on-site assessment survey and install a premise isolation backflow prevention device. For example, a private well system which feeds water to a property.

Back to the top