To help protect the safety of the City’s drinking water, it is mandatory under the City of Toronto’s Water Supply By-law for property owners of industrial, commercial, institutional and Part 3 residential properties (as defined by the Ontario Building Code) to install a backflow prevention device on the water supply line(s) to their facility. This is done to isolate buildings from the City’s water distribution system, helping to ensure contaminants do not enter drinking water.

A complete list of sectors required to install a device can be found in Schedule 5 of the Water Supply By-law.

Backflow is the undesired reversal of water flow against the normal direction. This can occur through back pressure or back siphonage.

Back pressure

  • Occurs when pressure in a private water system is greater than pressure in the City’s water supply system.
  • Can result in water from the private system forcing its way into the City’s distribution system.
  • Can be caused by pumps, elevated tanks, temperature increases in boiler systems, and other local pressure events.

Back siphonage

  • Occurs when pressure in the City’s water supply system is lower than pressure in a private system.
  • Can pull contaminated water from the private water system into the City’s distribution system.
  • Can be caused by nearby fire-fighting or watermain breaks.

There are two types of backflow prevention devices: Double Check Valve Assembly and Reduced Pressure Principle Assembly.

The type required in a building is based on the hazard level, which is listed by sector in Schedule 5 of the Water Supply By-law. Should you require assistance determining the correct device for your facility, please contact Toronto Water at 416-394-8888.

Double Check Valve Assembly (DCVA)

Double Check Valve Assembly showing two check valvesRequired for facilities classified as “moderate hazard.” It consists of two check valves, which help to provide protection in the event that one valve does not close tightly. As DCVA valves can fail with no visible warning, they must be tested at least once a year to ensure proper operation.

Reduced Pressure Principle Assembly (RP)

Reduced Pressure Principle Assembly showing two internally loaded check valvesRequired for facilities classified as “severe hazard.” It consists of two independently acting, internally loaded check valves, separated by a reduced pressure zone. RP devices must be installed in an area with adequate drainage and tested at least once a year.

Hiring a plumber

Backflow prevention devices must be installed by a plumber licensed with the City of Toronto. A list of qualified plumbers can be obtained by sending a request to backflow@toronto.ca. This list is for convenience only; the City of Toronto does not endorse or accept liability or responsibility for work completed by companies on the list. Property owners are encouraged to get several independent quotes before choosing a plumber.

Installation

Building permits

A building permit is required for all new installations and replacements. Permits can be requested online or over the counter, and are typically obtained by the plumber on behalf of the property owner.

Where to install a device

Devices should be installed immediately after the water meter and by-pass piping. This ensures that water from the private plumbing system will not flow back through the meter into the City’s water supply.

There must be no branch or hose connections between the water meter/by-pass and the backflow device. Thermal expansion must be addressed within the private plumbing system as per Part 7 of the Ontario Building Code.

RP devices cannot be installed below grade in a pit, chamber or vault. Discharges must be directed to a sanitary sewer.

Installation scenario

Complex image showing were Double Check Valve Assembly and Reduced Pressure Principle Assembly devices should be installed along the water meter. The image shows the direction of flow of water, the gate vale, outlet valve, outlet tee and devices placed at the end of the water meter.

  • Copies of any records submitted to the City should be kept on-site for a minimum of seven years.
  • The City must be notified of any changes to a property’s hazard level (i.e. due to tenant/operational changes). See Schedule 5 of the Water Supply By-law for hazard levels by sector.

Testing

  • Backflow devices must be tested:
    • at the time of initial installation
    • within 72 hours after a device has been cleaned, repaired, replaced, serviced or overhauled
    • at least once a year
  • Testing can be completed by plumbers, engineers and fire system sprinkler fitters certified as Cross Connection Control Specialists. See Schedule 6 of the Water Supply By-law for a full list of criteria for testers.
  • Test results must be reported on the Backflow Prevention Device Test Report and submitted to the City within seven business days.
  • Please ensure all forms are signed by the authorized tester and facility owner.
  • Incomplete test reports will be rejected and treated as non-compliant with the City of Toronto Water Supply By-law.

Test tags

  • A test tag that provides a historical record of test results must be attached to each device.
  • Tags can be any size and colour and should feature the following:
    • company name, address and logo
    • type and date of the device installation
    • manufacturer, serial number and size of the device
    • test date
    • tester’s name, initials and certification number
    • name of tester’s company

Surveying

  • Some property owners may receive a letter requesting that they complete a survey to help the City ensure adequate protection has been assessed.
  • Only certain professionals can conduct a survey. See Schedule 6 of the Water Supply By-law for a full list of criteria.
  • The following Backflow Prevention Survey Report (Excel I PDF) must be completed and submitted to the City by the date specified in the letter, or within 30 days.
  • The survey report must be signed by an authorized surveyor and the facility owner.
  • Surveys must be updated at least every five years, unless otherwise approved by the General Manager of Toronto Water, or within 30 days of any increase in hazard level.