Backflow Prevention

Backflow Prevention is the term used to prevent the reverse flow of water from a potentially polluted or contaminated source into drinking and bathing water supply systems. By installing a backflow prevention device, this risk is managed. There are a number of backflow prevention devices available to suit any particular situation.

backflow device
Figure 1: Typical Backflow Device

Examples of properties requiring backflow prevention:

  • Motels and Hotels
  • Vehicle repair workshops
  • Shops
  • Restaurants
  • Caravan parks
  • Medical and dental surgeries
  • Car and plant washing facilities
  • Dry cleaners and laundries
  • Hospitals and funeral parlours
  • Club houses for sports
  • Schools
  • Day care centres and kindergartens
  • Abattoirs

When does backflow occur?

The water supply system is designed to ensure your property is supplied with drinking water under pressure. If there is a drop in the supply pressure, there is a risk that water could flow backwards into the water main.

The water flowing back to the water mains could contain contaminates, foreign matter, or debris. This usually occurs when there is cross-connection between drinking and non-drinking water sources. The contaminated water can then come out of the mains supply at another location, with the potential to harm.

Backflow occurs because a condition exists in a water supply system that will cause back-siphonage or back-pressure.

Examples of how back-siphonage and back-pressure can occur:

Back-siphonage can occur on a property through a vacuum created in the water supply system. An example of back-siphonage would be a pipeline breakage, undersized pipework or high withdrawal rates.

Back-pressure occurs when the pressure within plant on a property exceeds that of the water supply mains. For example, a boiler that is chemically treated and has a higher discharge pressure than the mains supply can "force" the water back into the drinking water supply, contaminating it with chemicals.

Examples of potential source of contamination:

  • Fire services
  • Fire Hose Reels (FHR)
  • Irrigation systems
  • Vehicle maintenance pits
  • Vehicle/bin washing bays
  • Chemical injection areas
  • Alternative water supplies

What is the safeguard to prevent a backflow occurrence?

A correctly selected backflow prevention device (one-way valve) will eliminate any risk of contamination of the drinking water supply. Backflow devices are either testable or non-testable types with the selection dependent on the risk associated with the possible contamination.

Application and registration of a backflow prevention device

Council is required to keep a register in accordance with the Standard Plumbing and Drainage Regulation 2019.

The Licensed Plumber who inspects or tests a testable backflow prevention device must, within 10 business days after inspecting or testing the device, give local government written results of the inspection or test, along with payment of all relevant Fees and Charges.

Backflow Prevention Information Sheet(PDF, 582KB)

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