Under normal conditions, drinking water flows in one direction, from the Kemptville water distribution system, into a property’s private internal plumbing system. Drinking water naturally flows from areas of higher pressure to areas of lower pressure.

Backflow is the unintended reversal of water flow from a private building’s plumbing system back into the Kemptville water distribution system due to a loss or reduction in water pressure. This reversal can allow contaminants to enter the drinking water system. Backflow can occur due to back siphonage, back pressure and illegal cross-connections.

Back pressure occurs when the pressure within a building’s plumbing system exceeds the pressure in the Kemptville water distribution system. When this happens, water from the building system can be forced back into the municipal distribution system. Back pressure can result from pumps, elevated storage tanks, thermal expansion in boiler systems, or other localized pressure increases.

Back siphonage occurs when the pressure in the Kemptville water distribution system drops below the pressure within a building’s plumbing system. This pressure reversal can draw contaminated water from the private plumbing system back into the municipal distribution system. Back siphonage may occur during events such as water main breaks or large water demands from nearby fire hydrant use.

A cross connection is any temporary or permanent connection between a potable (drinking) water system and a source containing non-potable water, chemicals, or other substances that could enter the drinking water system through backflow or back siphonage. Examples include direct piping connections between the Kemptville water distribution system and industrial plumbing systems, heating/cooling systems, fire suppression systems, irrigation systems, or service lateral connections.

See Figure 1. for a diagram of a backflow prevention device for a residential property.

A backflow prevention device is a plumbing safety mechanism installed within a property to prevent contaminated water from flowing back into the clean potable water supply. It functions as a one-way valve system, typically using check valves and relief valves, to ensure water only flows in the intended direction and to prevent contamination caused by back siphonage or back pressure.

There are several ways to mitigate the potential for backflow:

• Provide a physical separation between drinking and non-drinking water systems.
• Install backflow prevention devices and assemblies.
• Maintain positive pressures in the distribution system.
• Implement backflow prevention programs.

Minor: any type of cross-connection or potential cross-connection that involves a substance that constitutes only a nuisance and results in a reduction in only the aesthetic qualities of the water and cannot create a danger to health.

Moderate: any minor hazard connection that has a low probability of becoming a severe hazard which includes, but is not limited to, connections involving water where the aesthetic qualities of the water have been reduced and, under certain conditions, can create a danger to health.

Severe: any type of cross-connection or potential cross-connection involving water that has additives or substances that, under any certain conditions, can create a danger to health.

Please refer to Schedule B of Water Use and Rate By-Law No. 64-20, as amended, for the hazard rating of each property type.  

Backflow prevention devices protect potable water systems from contamination using various methods based on risk level. Below are several examples of backflow prevention devices:

Double check valves (DCVA): Designed for low-hazard applications such as irrigation systems and fire sprinkler systems, this device helps prevent the backflow of non-toxic pollutants using two independent check valves.

Pressure Vacuum Breakers (PVB): Protects against back siphonage in moderate-risk irrigation systems and must be installed at least 12 inches above the highest downstream outlet.

Atmospheric Vacuum Breaker (AVB): A simple, cost-effective device used for lower-hazard applications, typically installed on individual zone valves. It is not designed for continuous pressure conditions

Reduced pressure zone (RPZ): Provides the highest level of backflow protection for high-hazard applications involving toxic or contaminated water, such as hospitals and industrial facilities. The assembly contains two check valves and a relief valve to prevent both back pressure and back siphonage.

As per Section D of Water Use and Rate By-Law No. 64-20 as amended, all residential, industrial, commercial, institutional, and multi-residential building property owners must abide by the following:

• Cross-connections that could allow contaminants to enter the municipal drinking water system are prohibited.
• Property owners must install and maintain appropriate backflow prevention devices where there is a risk of contamination, in accordance with the Ontario Building Code and CSA B64 standards.
• All irrigation systems connected to the potable water system require backflow prevention.
• Property owners are responsible for all costs associated with the purchase, installation, testing, maintenance, repair, and replacement of backflow prevention devices.
• The Municipality may inspect properties connected to the water system to verify compliance and may require cross-connection surveys or additional backflow protection if risks of contamination are found to exist.
• Failure to provide access, install required devices, complete testing, or comply with orders may result in the water service being shut off.
• Industrial, commercial, institutional, and certain multi-residential properties are required to complete cross-connection surveys and submit reports prepared by approved testers.
• Backflow prevention devices must be tested upon installation and annually thereafter by an approved certified tester.
• Test reports must be submitted to the Municipality within the required timeframe and devices must be repaired or replaced if found defective.
• Unauthorized use of hydrants is prohibited, and approved backflow prevention devices are required for any authorized hydrant use.
• Fire protection sprinkler systems must also have appropriate backflow prevention and annual testing.
• Only authorized and properly certified testers registered with the Municipality may conduct testing, inspections, installations, or repairs related to backflow prevention devices.

The North Grenville Cross Connection Control Survey form is available here.

Backflow preventers have internal components that can wear out over time. Annual testing is required to ensure the device is operating properly and providing adequate protection to the Municipal drinking water system. The Municipality of North Grenville’s Backflow Prevention Program monitors annual testing to help protect the integrity of the Municipal drinking water system.

The Municipality has contracted a third-party provider, BSI Online, to administer and track compliance with the Municipality's Backflow Prevention Program. BSI issues reminder notices when backflow preventer testing is due and maintains testing records on behalf of the Municipality. Property owners are responsible for arranging testing by a qualified backflow prevention tester and ensuring that completed test reports are submitted through the BSI online portal.

Customer Confirmation Number (CCN)

If your backflow device is registered and you have a Customer Confirmation Number (CCN), BSI provides a list of qualified testers and access to device compliance information through the BSI Online portal.

A CNN is generated by BSI to track registered premise isolation backflow devices. The CCN is used by certified testers to submit test results through the BSI Testers Portal, ensuring accurate tracking and compliance with the Municipality’s Backflow Prevention Program.

On March 7, 2005, a contamination incident in Stratford, ON occurred when a wax-based car wash cleaning solution entered the municipal water supply. The contamination originated at Festival U-Wash, where a backflow prevention device had been installed, but was bypassed through a connection to a booster pump. An open valve allowed a detergent containing 2-butoxy-ethanol to flow back into the city’s water distribution system.

Approximately 30,000 residents were affected, and 19 people sought medical attention. Parts of the city were without safe water service for nearly 7 days.

The business owners were fined $75,000 by the Ontario Ministry of the Environment, Conservation and Parks in 2006. The incident also cost the city an estimated $100,000 in staff overtime alone, with total costs likely much higher due to ongoing claims and response efforts.

Link: https://news.ontario.ca/en/release/83024/festival-u-wash-and-manager-fined-total-of-75000-stratford