1.    What is backflow?

Normal water flow goes from the City's pressurized water supply system to the consumer's plumbing system. Backflow is the reversal of the normal direction of flow. Backflow may occur due to either back siphonage or back pressure.

2.    What is a back siphonage?

Back siphonage is backflow caused by a negative pressure (i.e. a vacuum or partial vacuum) in a city's water supply system. It is similar to drinking water through a straw. Back siphonage can occur when there is large water demand for fire fighting, high velocities in pipe lines, watermain break or repairs that are lower than a service point.

3.    What is back pressure?

 Back pressure means that private water pressure is greater than the municipal water supply pressure. It can happen when there is a connection to a non-portable water supply operating at a higher pressure than the municipal water supply system. Higher water pressure can be created by booster pumps, thermal expansion in boilers, elevated piping, etc.
4.    What is cross connection?

A cross connection means any actual or potential connection between a potable water system and any source of pollution or contamination. Cross connection includes any by-pass, jumper connection, removable section of pipe, swivel or changeover device and any other temporary or permanent connecting arrangement through which backflow may occur.

5.    What happens after backflow occurs?

When backflow occurs, any contaminants that had a chance to enter the water supply will start to flow towards any point of use (plumbing fixtures inside the building, other businesses/buildings connecting to the water supply system). The degree of hazard to health is dependent on the type and amount of contaminant, the situation of water use points, whether or not a protective device is in place, etc.

6.    What does it mean to be in compliance with By-law?

To be in compliance with the By-law, a property owner has to complete all backflow prevention activities (i.e. survey, testing and device upgrade) required for their property in the required time frame and frequency.  
7.    How is the By-law enforced?

Markham is encouraging applicable property owners to comply with the By-law. Property owners should regularly log into their backflow prevention account at the City’s “Backflow Prevention Program Online Services” website to ensure that all backflow prevention work required for their property are completed. 

Those non-compliant or partial compliant property owners will receive Markham's Order to Comply notices by registered mail. Each notice will indicate the compliance due date.

The “Backflow Prevention Compliance Processing Fee” will apply to those property owners who have received the Order to Comply notice, but failed to comply within a compliance timeframe. In addition, necessary legal actions will be taken on those non-compliant and partial compliant property owners.

8.    Do I need to apply for a permit if I need to install a backflow preventer?

There are two categories of backflow preventer: one is testable and the other is non-testable.  Please consult with your Qualified Person for appropriate application of testable and non-testable backflow preventers.
A building permit is required for installation, replacement or relocation of a testable backflow preventer.

9.    What is premise isolation?

Premise isolation means backflow prevention provided at the municipal water connection to a building or facility.  Usually, the premise isolation backflow preventer is installed immediately downstream of the City’s water meter and meter by-pass. In the case of an un-metered fire service, the premise isolation backflow preventer must be installed on the customer’s property, upstream of any sprinkler system, stand pipe or private hydrant.

10.    What is area isolation?

 Area isolation means backflow prevention provided at a section of water piping within a building or facility which has potable and non-potable connections.  

11.    What is zone isolation?

Zone isolation means backflow prevention provided at a section of water piping within a building or facility which has only non-potable connections.  Usually, the zone isolation backflow preventer is installed at the water connection to a zone in the building, which only has non-potable connections. However, its downstream water piping must not be interconnected with its upstream water piping.

12.    What is source isolation or fixture isolation?

 Source isolation or fixture isolation means backflow prevention provided at the water connection to a fixture or appliance within a building or facility.  Usually, the source isolation or fixture isolation backflow preventer is installed right at the water connection point to a fixture or appliance.

13.    Can I just install premise isolation? Or do I need to install any premise isolation?

By installing premise isolation, backflow is only prevented from entering into the municipal drinking water supply. However, businesses and employees within the building are not protected from potential contamination due to backflow.  Markham's program requires installing a source isolation or zone isolation for all types of hazard classification. Also, for premises with a “severe” or “moderate” hazard classification, premise isolation is required on top of any source or zone isolations. A cross connection control survey report for each facility is still required under the By-law.

14.    What is a cross connection control survey?  How do I complete the related report?

A cross connection control survey shall be carried out starting at the water meter to all the plumbing within a facility as per CSA standards and Ontario Building Code.  It should identify all cross connections located within the facility.  The hazard level of each cross connection should be assessed and existing backflow protection of each cross connection should be identified as well. If no backflow prevention exists or the existing backflow protection is not acceptable, the acceptable backflow protection approach should be recommended.

15.    What is backflow preventer test and inspection?  How do I compete the related report?

A backflow preventer is a mechanical device and has internal seals, springs, and moving parts that are subject to fouling, wear or fatigue. All backflow preventers have to be tested and inspected periodically to ensure that they are in good working conditions and can function correctly.

16.    What is device upgrade implementation?  How do I complete the related paper?

Device upgrade implementation refers to installation of new backflow preventers, repair, replacement or relocation of the existing backflow preventers within a facility.  Markham’s Backflow Prevention Program requires the property owners to rectify all backflow prevention deficiencies identified on their Cross Connection Control Survey Reports or Backflow Preventer Testing & Inspection Reports.