What is Backflow?
Backflow is the unintended flow of water or other liquids from a potentially polluted source into the drinking water supply. It can occur anywhere drinking water is used and is caused by
cross-connection (direct or indirect physical connections of drinking and non-drinking water). Any liquid has the potential to flow backwards given the right conditions.
Backsiphonage and backpressure.
Backsiphonage is when the water flows backwards due to a sudden pressure drop whilst backpressure occurs when the outlet (downstream) pressure is greater than the supply pressure.
How serious is it?
At worst, backflow can cause death. Any property that has drinking water entering it is classified with a degree of seriousness of the backflow contamination risk known as the HAZARD RATING.
HIGH HAZARD is any condition in the water supply that can cause DEATH.
MEDIUM HAZARD is any condition in the water supply that can ENDANGER HEALTH.
LOW HAZARD is any condition in the water supply that can be a NUISANCE.
Selection of backflow and prevention devices.
First, it is necessary to identify the hazards within the property. Upstream from these hazards, the water is considered as non-drinking until a suitable backflow prevention device is installed. It may be necessary to install a backflow prevention device for a fixture, a zone within a building, or at the boundary of the property.
Levels of Protection.
Backflow prevention protection is provided at individual fixtures.
Backflow prevention protection is provided at the connection to specific sections of the water supply system within a building.
Backflow prevention protection is provided at the property boundary to protect the authority’s water supply from contamination.