Cross Connection Control Program

In the interest of maintaining safe drinking water, the City of Nanaimo has implemented a Cross Connection Control Program. Bylaw #7249 regarding Cross Connection Control was adopted on March 19, 2018. The purpose of this program is to ensure that non-potable water cannot be introduced into the City of Nanaimo water supply system due to a backflow situation.

The Cross Connection Control Coordinator performs assessments on existing facilities to determine whether there is a potential for contaminated water to flow back into the water distribution system. Backflow prevention devices are installed to stop this possible contamination.

Backflow Prevention devices are documented and tracked to ensure they are receiving annual testing. This annual testing must be carried out by a certified Cross Connection Control Backflow Assembly Tester.

Frequently Asked Questions

What is Cross Connection?

Any actual or potential physical connection whereby the potable water system is or would be connected directly or indirectly to a piping system containing non-potable water which could enter the potable water system as a result of backflow.

What is Backflow?

The reverse direction from normal direction of flow of water or used water, as a result of backsiphonage or backpressure.

What is Backsiphonage?

Backflow caused by negative or reduced pressure in the supply piping.

What is backpressure?

Backflow caused by downstream piping operating at a higher pressure than upstream piping.

Does water contamination due to backflow actually occur?

Although there have not been any reported backflow incidents in Nanaimo it is a well-documented and proven risk to the water supply system. There have been many incidents across the country and around the world; for example:

 In the town of Redcliff, Alberta, fertilizer from a greenhouse was backsiphoned into the Town’s water main and delivered to another customer who unknowing drank the contaminated water via his home faucet. The customer became violently ill within hours. This backflow incident occurred as a result of the Towns water main being shut off for repairs and the greenhouses lack of backflow protection.

Who owns the backflow prevention devices?

The owner of the business or facility is responsible for the installation, maintenance and renewal of any required backflow prevention devices.

Where are backflow prevention devices located?

Backflow prevention devices can be installed either where the water service enters from the road or in a mechanical room. There are potentially many options for locating the device. Work with a qualified plumbing contractor in conjunction with the City of Nanaimo Cross Connection Control Coordinator to find a suitable location.

Why are backflow preventers tested annually?

Annual testing of backflow devices is necessary to ensure the equipment is operating properly. It provides the City and water system users the confidence that appropriate risk mitigation is in place.

I have received a letter stating that I must have my backflow preventer tested. What do I do?

Coordinate with a certified tester to have the device tested and have them send the test report to the Cross Connection Coordinator.

How do I submit a backflow preventer test report?

Test reports are submitted to the Cross Connection Coordinator by the certified tester who has inspected and tested the assembly. Tests reports can by submitted by:

  1. Register at to submit test reports easily on your mobile device.
  2. Complete & Submit the City of Nanaimo Backflow Prevention Assembly Test Report online OR
  3. Print & Complete City of Nanaimo Backflow Prevention Test Report (pdf) and email copy to

What do I do if I am removing a backflow preventer and not replacing it?

  1. Complete & Submit the City of Nanaimo online Backflow Preventer Removal Report online OR
  2. Print & Complete City of Nanaimo Backflow Preventer Removal Form (pdf) and email a copy to

Last updated: August 9, 2023

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