What is backflow?
Water normally flows in one direction, from the City’s drinking water system to the pipes in your premises. Backflow is the flow of water in the opposite direction. Backflow can contaminate either the potable water within your building or the City’s drinking water system. There are two situations that can cause backflow:
- Back-siphonage, the pressure in the City’s drinking water system drops due to activities that draw a lot of water from the system (e.g., firefighting, water main breaks, cleaning the water mains). The water in your pipes is sucked back into the City’s drinking water system.
- Back-pressure , the pressure in your system increases (e.g., due to devices such as a booster pump, pressure vessel, pressure type chemical injector, boiler, or elevated plumbing). The water in your pipes is forced back into the City’s drinking water system
What is a cross-connection?
A cross-connection is an actual or potential connection between the drinking water supply and a source of contamination in a plumbing system. When a cross-connection is not properly protected, and a backflow situation occurs, contaminants can enter the drinking water system or the water pipes on your premises. An example is the common garden hose attached to a sill cock with the end of the hose lying in a cesspool. Other examples are a garden hose attached to a service sink with the end of the hose submerged in a tub full of detergent.
How is the type of backflow prevention device selected?
The device is selected based on the degree of hazard to public health and the type of backflow it is controlling. There are three degrees of hazard: Severe – any cross-connection or potential cross-connection to any substance that could be a danger to health. Severe hazards are typically found in industrial, commercial facilities, hospitals and mortuaries. Moderate – any minor hazard that has a low probability of becoming a severe hazard. Moderate hazards are typically found in office buildings, schools, shopping malls, and high-rise buildings. Minor – any cross-connection or potential cross-connection that is primarily a nuisance with a very low probability of becoming a health hazard. Minor hazards are typically found in residential homes, hair salons and restaurants.
Why do backflow prevention devices have to be tested annually?
Mechanical backflow prevention devices have internal seals, springs and moving parts that can become dirty and wear out. They must be tested annually with properly calibrated equipment to ensure they are working properly.
Who is responsible to test and maintain the backflow prevention device?
It is up to the property owner to ensure the device is installed correctly, properly maintained and repaired and tested at the time of installation, and once a year thereafter. Assemblies also need to be retested if any maintenance or repairs are performed on the device