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Frequently Asked Questions – Cross-Connection Control & Backflow

1. What is a cross-connection?

A Cross-Connection is any actual or potential connection between the municipal drinking water system and any source of pollution or contamination.

For example, a hose submerged in a sink or container full of dirty water or chemicals, under the right circumstances could draw the water from the sink or container back into the municipal drinking water system, causing possible contamination.

2. What is backflow?

Normally, water flows in one direction, from the public drinking water system through a property’s plumbing to a sink tap or other plumbing fixture. However, under certain conditions, water can flow in the opposite direction. This is known as backflow. Backflow occurs when backsiphonage or a back pressure condition is created in a water line.

3. What is backsiphonage?

Backsiphonage is when water flows in the opposite direction caused by a negative pressure in the water line. This can happen in any building where there is a reduction or stoppage of the main water supply pressure because of nearby firefighting, power outages, repairs or breaks in watermains.

4. What is backpressure?

Backpressure can be created when a source of pressure, such as a pump, creates a pressure greater than the one supplied from the water distribution system. For example, if a pump supplied from a landscape pond was accidentally connected to the plumbing system of a residents’ drinking water, the water from the pond could be pumped into the drinking water supply.

5. How is backflow prevented?

Backflow, whether caused by backsiphonage or backpressure, is prevented by eliminating the cross-connection and installing a backflow prevention device. In accordance with the CSA standard, Halton Region recognizes the following two types of premises isolation backflow prevention devices:

  • Reduced Pressure Principle Assembly (RP).Reduced Pressure Principle Assembly device.
  • Double Check Valve Assembly (DCVA). Double Check Valve Assembly device.
6. What is premises isolation?

Premises isolation is using a backflow prevention device to isolate the main municipal water supply from an industrial, commercial and institutional or multi-unit residential private plumbing system. This isolation prevents drinking water contamination caused by backflow, backpressure or backsiphonage.

7. How is the type of backflow prevention device selected?

Based on the property owner's completed cross connection control survey, Halton Region reviews the survey information and the recommendations made by the authorized OWWA accredited tester and advises you of the type of backflow prevention device needed.

8. Where are backflow prevention devices required to be installed?

Under Halton Region's Cross-Connection Control Program, backflow prevention devices are required on water service laterals for all:

  • multi-unit residential (greater than three stories)
  • industrial buildings
  • commercial buildings
  • institutional buildings
The devices are installed at the entrances to the building for new sprinkler services and on the customer’s side of the water meter for domestic services.


9. Where can I find someone to do this work for me?

The Region maintains a list of Authorized OWWA Accredited Testers who have submitted their qualifications to Halton Region to perform the services outlined on the Authorized Functions List (Appendix A). The Region recommends you obtain several quotes before selecting a tester and does not endorse or provide a warranty of the services, prices, or qualifications.

10. Who is responsible for the testing and maintenance of the backflow prevention device

The property owner is responsible for ensuring a backflow prevention device is in satisfactory operating condition at all times. The backflow prevention devices must be tested at the time of installation and on an annual basis thereafter. If any maintenance or repairs are performed on the device, the device must be re-tested. The property owner will receive a notice advising them when the annual test is required on the device.

Consult this list of authorized OWWA accredited testers. The Region recommends you obtain several quotes before selecting a tester and does not endorse or provide a warranty of the services, prices, or qualifications.

11. I am a tenant in a multi-unit property and received a letter from Halton Region. What should I do?

Please email us and give us the contact information for your property manager. We will redirect the letter accordingly.

12. Who pays for services related to backflow prevention devices?

The property owner has the full responsibility to pay for the cost of:

  • services of third party contractors
  • survey assessments
  • installation
  • testing, repairs and maintenance
  • plumbing permits and materials
The Region recommends you obtain several quotes before selecting an authorized (OWWA) accredited tester and does not endorse or provide a warranty of the services, prices, or qualifications.


13. What is a "moderate" or "high or severe" hazard?

Moderate hazard:

Means any minor hazard connection that has a low probability of becoming a severe hazard.

High or severe hazard:

Means any type of Cross-Connection or potential Cross-Connection involving substances that, under any concentration, is considered dangerous to health.