Annual testing is a legal obligation on the property owner, and the Illawarra is split between two water authorities with meaningfully different processes. Here is what is required, who has to do it, and what changes when you cross the line at Gerroa.
Sydney Water’s area of operations runs from the Hawkesbury River in the north down to Gerroa. That makes Gerroa the last town on its network. Everything from Berry south is Shoalhaven Water, under Shoalhaven City Council.
If you own or manage property on both sides of that line, you are dealing with two different processes for the same obligation. The comparison table further down sets out exactly where they diverge.
Backflow is drinking water travelling the wrong way — out of a property and back into the public main. It happens when pressure in the main drops, usually during a burst, a firefighting draw-off or maintenance, and whatever is connected on your side gets siphoned backwards.
That is why the risk categories are written the way they are. A garden hose left in a bucket of pool chemicals, a chemical dispenser in a commercial kitchen, or a dental console can all put something into the public supply that other people then drink. A backflow prevention device is a one-way barrier at the boundary that stops it.
The obligation to have the right device installed and maintained sits on the property owner, not on the plumber and not on the tenant.
Both authorities work from the three hazard ratings in AS/NZS 3500.1. Sydney Water publishes a rating-to-device mapping; Shoalhaven Water defines the ratings and leaves device selection to the Standard and the Plumbing Code.
| Rating | What it means | Device required | Tested? |
|---|---|---|---|
| Low | Could constitute a nuisance, but would not endanger health or cause injury. | 20 mm and 25 mm meters have an integral device built in. Meters larger than 25 mm need a separate non-testable containment device. | No |
| Medium | Any condition, device or practice that could endanger health. | Testable double check valve for drinking water connections. Double check detector assembly for fire service connections. | Yes — annually |
| High | Any condition, device or practice that has the potential to cause death. | Registered break tank, reduced pressure zone device (RPZD), or registered air gap. | Yes — annually |
Worth knowing: Sydney Water states that if you do not know your site’s hazard rating and do not get it assessed, it will assume the site is high hazard. It also treats any construction project larger than a single standalone house as a high backflow hazard. Getting an assessment done is often cheaper than being deemed into the most expensive device class.
Same obligation, two processes. The differences that matter most in practice are who lodges the paperwork, whether a survey is needed before approval, and what happens if you let it lapse.
| Sydney Water | Shoalhaven Water | |
|---|---|---|
| Who lodges the test result | Your plumber, through the Sydney Water portal | The property owner or their agent |
| How | Sydney Water Tap in / Backflow Prevention portal | Email to Council, or in person at Nowra or Ulladulla |
| Deadline to lodge | Within 2 days of the test | No stated deadline; annual cycle with about 4 weeks’ notice |
| Testing interval | On installation, then annually | On installation, then intervals not exceeding 12 months |
| Survey before approval | Not required as a formal document | Backflow survey letter required at DA stage, with 5 prescribed items |
| New installs inspected | Sample audits against AS/NZS 3500.1 and AS/NZS 2845 | Every new or replacement device inspected as part of registration |
| Register and reminders | Register kept, annual reminder sent | Register kept, notice about 4 weeks before due |
| Rating-to-device table published | Yes, detailed | No — defers to AS/NZS 3500.1 and the PCA |
| Registration fee | None published | Council fee payable |
| If you do not comply | May test and charge you, restrict supply, disconnect, and recover costs | An offence; late fees per 4-week period, per device |
| Time to fix a failed device | Not stated | 4 weeks from the test date |
The two-day lodgement rule is the one people most often miss on the Sydney Water side. On the Shoalhaven side it is that the duty to lodge sits with the owner, not the plumber — so if your plumber emails you the report and you file it in a drawer, you are the one who is non-compliant.
This step has no Sydney Water equivalent and catches people out. During a development application, or any time Council decides a proposed business activity might create a hazard, Shoalhaven Water asks for a backflow survey by an accredited backflow plumber or a hydraulic consultant.
The survey has to assess the whole site and every business activity on it, and must state:
Large or complex sites also need a hydraulic plan showing device locations and types. If a change of business activity means a device is no longer needed, a new survey has to go in before it can be removed.
For a strata scheme, the containment device sits at the point where the water service connects to the site and protects the whole building. Because it is not for the exclusive benefit of any single lot, it falls within the definition of common infrastructure, which makes it common property — and the owners corporation carries the statutory duty to maintain common property. In practice that means backflow testing is an owners corporation cost, funded from the administrative or capital works fund.
The exception is a device installed inside a lot to protect a hazard within that lot — a dental surgery, a hairdressing basin, a commercial kitchen in a mixed-use scheme. Those are generally the lot owner’s. Confirm the split with your strata manager before anyone commits to spending, because getting it wrong means someone gets billed twice or not at all.
One thing worth flagging for committees: since late 2025 NSW Fair Trading has had enforcement powers over the owners corporation duty to maintain and repair common property, including the ability to investigate, require documents, issue compliance notices and penalty infringement notices. An overdue backflow device is exactly the kind of documented, dated, register-tracked lapse that is easy for a regulator to establish.
More on strata plumbing compliance, or see our strata plumbing services.
Sprinkler and fire hydrant connections each need a testable double check detector assembly, installed close to the water service entry and upstream of any booster assembly. Galvanised pipe and fittings are not permitted upstream of the device, and upstream materials must be WaterMark approved.
Fire hose reels also require backflow protection and must be supplied from metered services. Window and wall drenchers are treated as low hazard and take a non-testable device at the point of connection.
Under the National Construction Code, a property with a separate fire water service is rated medium hazard for containment purposes — which means the device on it is testable, and testable means annual.
Hazard ratings below follow the National Construction Code’s cross-connection hazard schedule. The device column follows Sydney Water’s published mapping and is indicative — the actual device depends on a site assessment.
| Property use | Hazard | Typical device |
|---|---|---|
| Commercial kitchen | High | RPZD, registered break tank or registered air gap |
| Dental surgery, clinic or day surgery | High | RPZD, break tank or air gap |
| Car and plant washing facilities | High | RPZD, break tank or air gap |
| Irrigation with fertilisers or pesticides | High | RPZD |
| Chemical labs, abattoirs, petroleum plants | High | RPZD, break tank or air gap |
| Separate fire water service | Medium | Double check detector assembly, upstream of the booster |
| Apartment blocks above the small-scheme threshold | Medium | Testable double check valve |
| Small residential flat building, limited chemicals | Low | Integral meter device, or non-testable device if the meter is over 25 mm |
| Above-ground rainwater tank | Low | Integral meter device on 20/25 mm meters |
| Below-ground rainwater tank | Low | Vented dual check valve with atmospheric port |
Backflow devices are selected and installed under AS/NZS 3500.1:2021, Section 4. The devices themselves are made to AS/NZS 2845.1:2022, and the annual field test is performed to AS/NZS 2845.3:2020. Above those sits Part B5 of the National Construction Code, Volume Three — cross-connection control — with its schedule of cross-connection hazards.
There is one interaction worth understanding, because it is the reason this page exists. Building Commission NSW notes that regulations issued under water supply legislation may prescribe containment protection that differs from the Code’s schedule, and where that happens, the water authority’s rules are the ones to follow. That is precisely why Sydney Water and Shoalhaven Water can require different things for the same building.
As at August 2026, NCC 2022 Volume Three is the edition in force for plumbing in NSW. NSW adopts NCC 2025 on 1 May 2027.
The Illawarra also sits inside the area Building Commission NSW audits directly, which means a Notice of Work before starting and a Certificate of Compliance on completion go to the Commission. In the Shoalhaven, those go to the local plumbing regulator instead.
If your property has a connection to a water or recycled water main — including a separate fire service connection — you need containment backflow prevention. Sydney Water is explicit that connections to its water and recycled water pipes, including fire service connections, need containment devices. The level of protection depends on your hazard rating, and if you have never had the site assessed, Sydney Water will assume it is high hazard by default.
High and medium hazard testable devices must be tested when they are installed and every year afterwards, by an accredited backflow plumber. Shoalhaven Water words it as intervals not exceeding twelve months. Low hazard non-testable devices, such as the dual check valve integral to a 20 mm or 25 mm meter, are not field tested.
A licensed plumber holding backflow accreditation. Sydney Water names the specific unit of competency: CPCPWT4022, Commission and maintain backflow prevention devices, completed through a registered training organisation. Worth knowing that neither Sydney Water nor Shoalhaven Water accredits plumbers themselves — both keep voluntary contact lists and both state plainly that the plumbers on them are not affiliated with or accredited by the authority.
It depends which authority you are under, and the difference is significant. Sydney Water states it may test the device and charge you for the service, restrict your water supply, disconnect you, and charge you any costs it incurs to make your connection satisfy its requirements. Shoalhaven Water treats failure to register as an offence, with late fees applying for each four-week period, or part of one, that each outstanding device is overdue.
No. Berry is Shoalhaven Water, under Shoalhaven City Council. Sydney Water's area of operations ends at Gerroa, so Wollongong, Kiama, Shellharbour, Gerringong and Gerroa are Sydney Water while Berry and everything south is Shoalhaven Water. The requirements are similar in substance but the process differs in several practical ways, including who lodges the test report and whether a survey is needed up front.
Generally the owners corporation. A containment device sits at the point where the water service connects to the site and serves the whole building, so it is not for the exclusive benefit of any one lot — which makes it common infrastructure and therefore common property, and the owners corporation has a statutory duty to maintain common property. A device installed inside a single lot to protect a hazard within that lot, such as a dental surgery or a commercial kitchen in a mixed-use scheme, is generally the lot owner's. Confirm the split with your strata manager before anyone commits to spending.
Yes. Sydney Water requires a testable double check detector assembly on each sprinkler and fire hydrant connection, installed close to the water service entry and upstream of any booster assembly. Galvanised pipe and fittings are not permitted upstream, and upstream materials must be WaterMark approved. Fire hose reels also need backflow protection and must be supplied from metered services.
No regulator publishes a benchmark. Sydney Water, Shoalhaven Water, IPART and NSW Fair Trading all decline to set or publish a figure, and any "typical NSW cost" you see quoted online comes from a competitor's marketing page rather than an official source. Call us and we will quote your site — the cost depends on the number of devices, their type and access. Note that Shoalhaven Water does charge a council registration fee on top of the plumber's testing fee; the current amount is available from Council.
We test and certify backflow devices across the Illawarra under both Sydney Water and Shoalhaven Water requirements, and we handle the lodgement so it does not sit on your desk.
Reviewed 23 August 2026. This page explains published requirements and is not legal advice — the authoritative source is always your water authority and the current Standards. NSW adopts NCC 2025 on 1 May 2027, at which point this page needs review.