Backflow prevention

Requirements and registration

'Backflow' is water that flows backwards into our pipes after a property has used it. This water may carry contaminants that can harm people's health. That's why backflow prevention is so important, and backflow prevention containment devices must meet our connection requirements. We have a guide that provides information for backflow prevention (1MB) containment and a collection of frequently used Backflow prevention terms (66KB).

Register now to submit backflow test reports
Register for backflow prevention using a valid email address. If you're registered with Sydney Water Tap in®, you can submit an access request to the backflow prevention application quoting your Tap in login details.

When a site needs backflow containment

All connections to our water mains must have suitable backflow containment as set out in our policy, Your responsibilities when connected to our services (358KB).

What plumbers must do

Licensed plumbers must assess each site to work out its specific backflow containment needs.

If you've determined the site's hazard rating as low, our 20 mm and 25 mm water meters already have a simple backflow prevention device in them. If the property's water meter is larger than 25 mm, you'll need a separate backflow device. Find out more about meters and metered standpipes.

You must advise the property owner of the backflow requirements and install a backflow prevention device appropriate to the property's hazard rating. You must also tell the owner if the device needs to be tested each year.

What to know about fire services

All fire services, fire hydrant and sprinkler services require the installation of a Double Check Detector Assembly (DCDA).

The materials used on the upstream side of the DCDA and including the outlet control valve must be WaterMark approved for plumbing and drainage installations.

There can be no galvanised pipe and fittings on the upstream/inlet side of the containment device.

  • All rising spindle valves must be WaterMark approved.
  • All butterfly valves must be WaterMark approved and gear operated.

If you need further information, email us at

Who to contact about zone and individual devices

We no longer accept reports for zone and individual backflow devices. Contact NSW Fair Trading if you have questions about these types of devices.

Who can install or test backflow prevention devices

Only licensed plumbers with backflow prevention accreditation issued by a registered training organisation (backflow plumbers) can inspect, commission and test medium and high hazard backflow devices.

Once backflow devices have been installed, only backflow plumbers can test them. Once a test has been done, backflow plumbers must submit the test report using our online lodgement system.

Soon, all plumbers will be able to tell us about the installation of low hazard devices via Sydney Water Tap in.

Are you on our list of backflow plumbers?
If you're accredited and want to be on our list of backflow plumbers, email a copy of your Certificate of Attainment to or call us on 13 20 92 8am–5:30pm Monday to Friday (except public holidays). To become an accredited backflow plumber, visit TAFE NSW and search for 'plumbing' or 'backflow'.

Why you need to retain photos for each lodgement

We now audit lodgements.

As part of our audit, we may ask you to provide 2 photographs for any backflow containment device test you've registered with us. The photos need to show:

  • the backflow device you tested with the serial number clearly visible
  • the test kit you used.

You don't need to attach photographs to your test reports when you upload them using the new backflow prevention application. However, your uploaded test reports may be subject to an audit. If we audit your lodgement, we'll send you an email asking you to email the photographic evidence to us as proof.

Your first test report
We won't audit the first test report you upload using the new backflow prevention application. However, we will audit second and future test reports.

How to submit a backflow test report

Use our online lodgement system to submit your backflow test report. To access the system for the first time, you'll need to register for backflow prevention using your personal email address. If you can't access the system, email us at