Backflow prevention and cross-connection control


Backflow is the unwanted flow of potentially contaminated water that poses a risk to public health being drawn back into the drinking water supply. It can occur in two ways:

  • Back siphonage from a negative pressure in the main, or
  • Backpressure from downstream pressure becoming greater than upstream pressure.

Cross connections are actual or potential connections between the drinking water supply and a potentially contaminated source.

Protecting our water supply

Depending on the onsite business activity, there are different backflow prevention devices designed to minimise the risk of a potential contamination.

Under AS/NZS 3500.1 the three hazard ratings are:

  • High hazard – any condition, device or practice that has the potential to cause death.
  • Medium hazard – any condition, device or practice that could endanger health.
  • Low hazard – any condition, device or practice that could constitute a nuisance but not endanger health or cause injury.

Please note: Devices of high or medium risk must be tested annually by an accredited backflow plumber to ensure correct operating conditions, and device configuration complies to current standards. 

New and existing developments

During the development application process or at any time where it is determined by Council that there may be a potential hazard from a proposed business activity, we will ask you to obtain a backflow survey undertaken by an accredited backflow plumber or a hydraulic consultant/engineer.

The survey is required to assess the entirety of the site and all business activities on the premises. 

Backflow surveys can be submitted in the form of a signed letter or statement which includes the following information:

  • Hydraulic consultant or plumber’s name, address and qualifications (e.g. license number);
  • Address of property being surveyed;
  • Hazard rating of property;
  • Type and location of proposed device/s; and
  • Certify that the hazard rating, type, and location of devices have been determined, selected, and located in accordance with the PCA and AS/NZS 3500.1

For large or complex sites, the survey shall be accompanied by a hydraulic plan showing location and type of backflow devices proposed. 

Backflow surveys can be submitted by emailing

Device registration

Under current regulations of the Plumbing Code of Australia and Australian Standards AS3500, it is required that the property owner of an installed backflow prevention device:

  • Ensure new device/s are registered with Shoalhaven Water by providing an initial test report.
  • Provide annual test reports issued by a licensed, accredited backflow plumber.
  • Pay relevant council registration fees.
  • Ensure that any failed device is rectified within four (4) weeks of the test date. Council must be advised in writing of any unforeseen delays in the completion of works and a reasonable completion date agreed upon or late fees will be applied. 

Any new or replacement device/s will be inspected for correct installation as part of the registration process.

If test report does not comply, or our inspection finds that the installation is not correct to Australian Standards, we will be in contact with you and your plumber. 

All test reports are to be submitted by emailing, or can be submitted into our Nowra or Ulladulla offices. 

Please note: Failure to comply with registration is an offence and late fees will apply for each four-week period (or part thereof) overdue, for each outstanding device, until registration complete.

Change of business activity

If you believe a device is no longer required at a property due to a change of business activity, a new survey will be required to be submitted to Shoalhaven Water. If approved, you will be notified that the device may be removed.