What is backflow?

Backflow is caused when water pressure within your property is higher than the water pressure at the mains or if there’s a drop in pressure at the main. When backflow occurs the flow of the water direction is reversed and the water flows backwards into the water pipes, this is when cross contamination can occur.what is backflow4

Some common causes of reduced water pressure include:-

  • broken water main
  • the water outlet at the property is higher than the water main
  • heavy water use down stream, reduces upstream pressure
  • water being pumped from the mains during a fire

Backflow can become hazardous if your water supply becomes interconnected with a source of pollution, the pollutants can enter the water supply resulting in cross contamination.

Backflow risk ratings

Risks can be classed as low, medium or high as per AS/NZS 3500.1:2015.

  • Low risk – any condition, device or practice in connection with the drinking water supply system that constitutes a nuisance but does not endanger health or cause injury.
  • Medium risk – any condition, device or practice in connection with the drinking water supply system that could endanger health.
  • High risk – any condition, device or practice in connection with the drinking water supply system that could cause death.



In Western Australia it is mandatory if your property falls within the risk ratings, to have a backflow system installed and tested every 12 months to prevent risk of water contamination. Businesses are responsible to ensure relevant backflow systems are installed, tested and maintained annually, by a certified and licensed backflow technician.

Neglecting this responsibility may cause contamination and result in various fines from the Water Corporation of Western Australia.

Other reasons why businesses need water backflow prevention include:

  • Not having a backflow prevention device is dangerous. Cross- connections in water supply has the potential to allow contaminants into the drinking water, if consumed, can lead to developing gastrointestinal illnesses such as diarrhoea, vomiting and abdominal cramps.
  • Fines and penalties. Failure to comply with your backflow obligations can result in hefty fines anywhere from $500.00 to $5,000.00. There is also the risk of being sued by those effected by neglect to protect your water supply.
  • A water filter alone will not fully prevent water contamination. A water filter acts as a physical barrier against water impurities, but isn’t always enough to have consistently safe drinking water. With the installation of a backflow valve, it empowers the anti-water contamination function of water filters by preventing water pollution due to backflow.

Backflow laws

The Water Corporation of Western Australia is the body for enforcing backflow legislations and the requirement to have and maintain backflow prevention devices at the boundary of a property under the following regulations:

• Regulations 42 and 43 Water Services Regulations 2013

Due to the potentially serious nature of a backflow incident, Water Corporation can in accordance with these regulations serve an order on a property owner or occupier to install backflow devices.

The regulations also provide for penalties (up to $5,000.00) for non-compliance under the Water Services Act 2012 (WA). Water Corporation has the power to restrict or disconnect water services, to protect the drinking water supply from potential contamination caused by a backflow event from a property.

Want to know more? Further information on backflow laws can be found by clicking here!

Who can install and test backflow devices?

Only licensed plumbers who are qualified to install, test and certify backflow prevention devices are permitted to carry out works on backflow systems. Always ensure you are using a licensed backflow tester, prior engaging their services, you can check the watercorpration smart tester register by clicking here, or contact us @ Perth Backflow Specialists to take care of your backflow works.


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