Backflow is the unintended flow of water or other liquids from a potentially polluted source into the drinking water supply.
WHERE CAN IT HAPPEN?
ANYWHERE drinking water is used!
HOW DOES IT HAPPEN?
Cross connections are direct or indirect physical connections of drinking and non-drinking water. Any liquid has the potential to flow backwards given the right conditions.
Backsiphonage is when the water flows backwards due to a sudden pressure drop.
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 which can cause DEATH.|
|MEDIUM HAZARD - is any condition in the water supply which can ENDANGER HEALTH.|
|LOW HAZARD - is any condition in the water supply which can be a NUISANCE.|
SELECTION OF BACKFLOW & 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 INDIVIDUAL PROTECTION
Backflow prevention protection provided at individual fixtures.
Backflow prevention protection provided at the connection to specific sections of the water supply system within a building.
Backflow prevention protection provided at the property boundary to protect the authority's water supply from contamination.