For homeowners around Wollongong and the broader Illawarra region

Introduction: What is backflow prevention and why do bidets need it in Australia?
The thought of adding a sleek modern bidet seat might feel like a luxury bathroom upgrade. But beneath the shine sits a less glamorous, yet vital, issue: backflow prevention.

Simply put, backflow prevention stops used water or potential contaminants from flowing the wrong way into your clean water supply. In a home with a bidet (especially when connected to the toilet line), regulators treat it as a higher‑risk fixture. That’s why, in NSW, installations like these require careful hazard assessment and the correct backflow protection device. Read the NSW guidelines here.
Installing a bidet without proper protection is more than just a code slip‑up.

It exposes your drinking water supply to potential contaminants (because bidets are connected near hygiene zones)

How backflow happens: Back‑siphonage vs Back‑pressure explained in simple terms

• Back‑siphonage: Imagine the pressure in the street water main drops suddenly (perhaps due to a main break or firefighting flow). That drop can “pull” contaminated water from a fixture like a bidet back into the drinking supply.
• Back‑pressure: Conversely, if on‑site pressure rises relative to the supply (for example due to a booster pump or thermal expansion), it can push water back into the main line.
  Either mechanism can lead to contaminated water entering your home’s potable system—so effective backflow prevention matters.

Do I need a backflow preventer for a bidet in Wollongong? Common scenarios and answers

Short answer: Yes, very likely. Let’s break down some typical cases around Wollongong:

• Handheld spray next to a toilet: This is high hazard by definition (because the hose can reach near the bowl). You’ll almost always need a dedicated high hazard device (like a RPZ) installed by a licensed plumber.
• Bidet seat with visible air‑gap above rim: If the manufacturer lists an integral barrier (air gap or vacuum breaker) and the outlet is 25mm+ above the overflow level, this may reduce the need for an external device,but you’ll still need to check the WaterMark listing and your plumber should verify.
• Smart toilet/bidet combo with no visible gap: This is high risk; unless the product clearly has certified integral protection you’ll require an external device and annual testing.
  If you are in the Wollongong‑Shellharbour area and not sure which scenario fits you, the team at CS Plumbing & Drainage Services can evaluate your installation and advise.

Choosing the right device: RPZ, vacuum breakers, dual‑check valves, and air‑gaps

In NSW high‑hazard situations typically require one of the following:

• Reduced Pressure Zone Device (RPZ): spring‑loaded assembly that vents to atmosphere when pressure wrong way.
• Registered Air‑Gap (RAG): physical separation in line (no mechanical parts).
• Atmospheric Vacuum Breaker (AVB): prevents back‑siphonage, sometimes part of the fixture.
• Dual/Double Check Valve: sometimes for medium hazard but not sufficient for high hazard in many cases.

Your licensed plumber will choose the correct device based on your hazard rating, pressure conditions, and plumbing layout in your Wollongong location.

Product labels and approvals: WaterMark certification, pressure ratings, and temperature limits

Make sure your bidet or smart toilet has a WaterMark licence. On the WaterMark database the “scope of use” will show if integral backflow protection is included. Without that, you’ll need an external device.

Installation basics: Where backflow devices sit in a bidet installation

Typically:

• The bidet’s cold water feed line gets a high‑hazard device (RPZ etc) upstream of the fixture.
• Alternative: If multiple fixtures on same branch pose risk, a “zone” protection device may be used (though each bidet needs assessment).
  In Wollongong residences the plumber may route a dedicated branch or re‑use an existing branch—but layout, access, and test access matter.

Licensed plumber installation and compliance checks: When DIY is okay and when it’s not

In NSW, you must use a licensed plumber and accredited backflow tester for high hazard devices. Attempting to do a DIY bidet install without assessing backflow hazard could void your insurance, breach codes and threaten your water safety.
Your plumber should issue a certificate of compliance and your water company may also ask for a a backflow test certificate to be lodged.

Budgeting and timelines: Device costs, installation fees, and ongoing testing

For a typical Wollongong home installing a high‑hazard backflow device for a bidet:

• Parts + labour for device installation might vary depending on location, access, pressure testing and plumbing layout.
• Annual testing: Once installed it needs yearly test by accredited tester. Time and fee apply.
  Better to allocate upfront budget and factor in ongoing costs rather than surprise later.

Buying checklist: Questions to ask retailers and your plumber before installing a bidet seat

Always do your research for bidets that are sold in Australia, you do not want to purchase an expensive seat that does not meet Australian plumbing guidelines

• Does the bidet seat have a WaterMark licence number?
• Does its “scope of use” include integral backflow protection?
• Is the outlet at least 25 mm above the pan overflow level?
• What device will the plumber install if integral protection is not present?
• What are the ongoing obligations (testing, registration) for this device under NSW law?
  Make sure your plumber quotes these items clearly.

Want More Advice about a Bidet Or Bathroom Upgrade?

A bidet can be a fantastic addition to your bathroom in Wollongong, better hygiene, modern feel – but only if installed correctly with appropriate backflow protection.

For most homes, that means confirming WaterMark certification, selecting the right device for the hazard rating, and scheduling the required annual tests.
If you’re ready to explore your bidet upgrade, let CS Plumbing & Drainage Services help you pick the right solution for your bathroom and install it safely.

FAQs for Bidets and Backflow

Do all handheld bidet sprays need a backflow preventer?

Yes. In almost every case, handheld bidet sprays are treated as high-hazard fixtures because the nozzle can sit close to or inside the toilet bowl. This creates a real risk of contaminated water entering your household supply if a backflow event occurs. As a result, these fixtures require a testable high-hazard backflow prevention device, such as an RPZ, installed by a licensed plumber.

If my bidet seat has an integral air gap, do I still need anything else?

Possibly. A certified integral air gap or vacuum breaker may eliminate the need for an additional device at the seat itself, but your local water authority may still require a separate containment device at the meter depending on the property’s hazard rating. Always verify the bidet’s WaterMark certification and consult your plumber to confirm full compliance.

Who’s allowed to install and test these devices?

Only licensed plumbers can install backflow prevention devices, and only accredited backflow testers are permitted to carry out annual testing on high-hazard setups. If you’re installing a bidet or upgrading your bathroom in the Wollongong region, make sure your plumber is authorised and experienced with this type of work, as reports and certificates often need to be submitted to your local water utility.

How often do I need to test a high-hazard device like an RPZ?

Every year. High-hazard backflow devices must be tested annually to ensure they are working correctly. After the initial commissioning test, accredited testers must check the unit once every 12 months and provide a compliance report. This testing schedule helps keep your home safe and ensures ongoing compliance with NSW plumbing regulations.