Backflow (Cross-Connection) Prevention
In water supply systems, water is normally maintained at a pressure to enable water to flow from the tap, shower etc. When water system pressure drops or declines, contamination may be drawn into the system.
|Key Cross-Connection Terms and Definitions|
|Cross-connection||Any actual or potential connection between the public water supply and a source of contamination.|
|Backflow||The flow of water or other liquids, mixtures, or substances into a potable supply of water. Backsiphonage is one type of backflow.|
|Backpressure||Backflow that occurs when the pressure in non-water system sources exceeds the pressure in the water supply.|
|Backsiphonage||Results from negative pressures in the potable water supply.|
Where Can Cross-Connections Occur?
Cross-connections can occur at many points throughout a distribution system and a community's plumbing infrastructure. Cross-connections can be identified by looking for physical interconnections between a customer's plumbing and the water system. Some specific examples are:
- Lawn chemicals backflowing (backsiphoning) through a garden hose into the distribution system.
- Backsiphonage of "blue water" from a toilet into a building's water supply.
- Carbonated water from a restaurant's soda dispenser entering a water system due to backpressure.
- Backsiphonage of chemicals from industrial buildings into distribution system mains. Backflow of boiler corrosion control chemicals into an office building's water supply.
- Backflow or cross-connection with fire suppression systems containing anti-freeze.
What Technologies are Available to Control Cross-Connections & Prevent Backflow?
The type of backflow that is most likely to occur in your system (either from backpressure or backsiphonage) and the related health effects will determine which backflow prevention technology is best for your water system. The available technologies are described briefly below. Backflow prevention devices can protect your health and are mandatory to safeguard public health.
| Technology|| Description|
|Atmospheric Vacuum Breaker|
|Double Check Valve Devices|
|Reduced Pressure Zone Backflow Devices|