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How Backflow occurs
Interactive Backflow Presentation
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Backflow occurs when a contaminated source enters the water supply. The contaminated source can enter through a cross connection with the drinking water supply.
The water supply system is designed to ensure that water flows to your property under pressure. If this pressure is not maintained, there is a chance that water could be drawn back into the mains of Sydney Water.
Step 1 - Water pressure can be affected when:
- there is a break in the watermain
- water is being pumped from the main water supply during a fire
- a customer is using water at a higher pressure than the pressure supplied by Sydney Water (back pressure)
- heavy water usage downstream, reduces water pressure upstream.
- the water outlet on the property is higher than the watermain causing a constant back pressure
Step 2 - There is a cross connection between the drinking water supply and a contaminated source
There is a risk to public health if there is a cross connection between your water and a contaminated source. If there is a pressure drop in the main, a vacuum could be created in the water supply system which, under certain conditions, creates a siphoning effect and draws liquid from a contaminated source back into the drinking water supply.
Step 3 - A nearby property uses the drinking water supply
The dangerous chemical (or contaminant), which can remain in the watermain for a period of time, will then go down the watermains and into a nearby property. When this water is used for drinking, showering, household or business purposes the occupants could be seriously or fatally injured.
