Backflow Prevention Program Frequently Asked Questions

Backflow is when water flows the opposite direction from private property into the water distribution system – which could potentially add pollutants and contaminants into clean drinking water.

Backflow can happen because of either “back siphonage” or “back pressure” occurring within the watermain.

Backflow prevention means avoiding the backflow of water (which might contain pollutants and contaminants) back into the drinking water supplied by the City.

Back siphonage is caused by a negative pressure in a public water system. Back siphonage can occur when there is an interruption in water supply due to nearby firefighting, watermain breaks or routine maintenance.

Back pressure occurs when there is water pressure that is greater than the municipal water system supply pressure. It can happen when there is a connection to a non-potable supply operating at a higher pressure than the water distribution system. Some common examples that cause back pressure are elevated storage tanks, boiler systems and water booster pumps.

A backflow preventer is an assembly of valves installed in the plumbing system which prevent water from flowing in wrong direction. Some types of backflow preventers require regular testing to ensure they continue to work properly.

Cross connection are any actual or potential physical connection between the drinking water system and any other system which could potentially introduce contaminants into the City’s drinking water supply system.

Some examples of unprotected cross connections found in plumbing systems include:

• a water softener discharge hose directly connected to a floor drain.
• a chemical sprayer attached to a hose.
• a high-pressure washer utilizing soaps or cleaners connected to a hose or plumbing system.
• a lawn irrigation system installed without a backflow preventer.
• an auxiliary water source (e.g. well) connected to a municipal water system.

This by-law was put in place to maintain and protect the quality of the City’s drinking water. It is consistent with the City’s Drinking Wate​r Quality Management System, which is in place to provide safe drinking water to residents and businesses.

The Backflow Prevention By-law 117-2020 (PDF) applies to existing and new industrial, commercial, and institutional buildings, as well as mixed-use and multi-use residential properties.

All backflow preventers to be registered under this program shall be installed on the incoming water service line directly after the City of Vaughan water meter which will provide premise isolation within the plumbing system.

The use of a backflow preventer to isolate the main municipal water supply from private side plumbing systems. This prevents contamination of the drinking water within the water system caused by backflow created by back siphonage or back pressure.

No. The Backflow Prevention Program involves installing a backflow preventer on the drinking water service lines as it enters the building. A back-water valve is installed on the wastewater service connection as it enters the building. Learn more about the sanitary back-water valve.

Requirements for property owners to install a backflow preventer will be phased in over a five- to seven-year timeframe.

Please refer to your lease agreement regarding who is responsible for completing items that include but are not limited to Cross Connection Control Surveys, maintenance or installation(s) of a Backflow Preventer or modifications to the plumbing system within a tenant space.

The owner of the backflow preventer is responsible for ensuring it is tested annually and operating at all times. If at any time during the year maintenance or repairs are performed on the backflow preventer, the City must be informed immediately, and the backflow preventer must be re-tested.

Mechanical backflow preventers have internal parts that can wear and tear, so they must be tested from time to time to ensure they are working properly. There are various types of backflow preventers available. Whichever backflow preventer you are required to install, make sure it is tested by someone who is trained, qualified and registered with City of Vaughan Backflow Prevention Program.

Testable backflow preventers, such as Double Check Valve Assembly (DCVA) and Reduced Pressure Principle Assembly (RP), need to be tested upon installation, when repaired, relocated, annually or when requested by the City.

The City of Vaughan is contacting properties based on the potential hazard level the property has on the water distribution system. Properties which are classified as a Severe Hazard will be contacted first, followed by those properties classified as a Moderate Hazard and a Minor Hazard.

Only Qualified Companies who are approved and registered with the Backflow Prevention Program and who employ Qualified People can survey properties, install and test backflow preventers. Any work completed by companies or persons not registered with the program will not be accepted and will be considered non-compliant.

Please see the list of Approved Qualified Companies (PDF).

Yes. Property owners have the ability to use another contractor that is not an Approved Qualified Company. The contractor must provide the City with all required documents as outlined under the Authorized Function List (PDF) along with a registration fee for the review and approval process before they start any work.

Disclaimer

Please note that the City of Vaughan will not recommend or endorse any Qualified Company and/or Qualified Person(s) registered to this program and makes no representation about the quality of work a Qualified Person and/or Qualified Person is able to provide. Property owners are encouraged to conduct their own due diligence when retaining a Qualified Company and/or Qualified Person.

Under no circumstances will the City of Vaughan be responsible or liable to any contractors completing works done pursuant to the Backflow Prevention By-law, nor to any property owner procuring services pursuant to the Backflow Prevention By-law.

Property owners will need to acquire a building (plumbing) permit for the installation or an addition of a new backflow preventer. A permit is also required when a backflow preventer is relocated or replaced with one that is not identical to the existing backflow preventer.

Please contact Building Standards at 905-832-8510 or buildingstandards@vaughan.ca. Office hours are ​Monday to Friday, 8:30 a.m. to 4:30 p.m., except public holidays.

• Ontario Water Works Association - Backflow Prevention
• Ontario Building Code – Part 7 Plumbing