Bidet Installation Requirements in Australia: Plumbing Code and Backflow Protection Explained

Introduction

Bidet toilet seats, bidettes and handheld bidet sprays (douche sprays) are becoming increasingly common fixtures in Australian residential bathrooms. While many of these products are marketed as simple retrofit accessories, their installation introduces potential cross-connection risks that must be carefully managed to protect the drinking water supply.

The Plumbing Code of Australia (PCA) and AS/NZS 3500.1:2021 establish requirements for managing these risks, particularly where fixtures may allow contaminated water to be drawn back into the potable water system.

This paper outlines the regulatory framework governing the installation of bidet toilet seats, bidettes and handheld bidet sprays, and clarifies the requirements relating to WaterMark certification, hazard classification and backflow prevention.

Regulatory Framework

The Plumbing Code of Australia addresses the risks associated with cross-connections through Specification 41 – Materials and Products (S41C4 Individual Protection).

Under this specification, certain fixtures are classified as high hazard connections where they have the potential to contaminate the drinking water supply.

Specification 41 identifies the following fixtures as high hazard for the purpose of individual protection:

6. Bidets and toilet douche seats where the outlet in any position is not 25 mm above the overflow level of the pan.
7. Bidettes installed without a minimum 25 mm air gap.
8. Handheld bidet or douche hoses and trigger sprays.

Handheld bidet/douche hoses and trigger sprays must hold current WaterMark approval to be permitted to be connected to a drinking water supply.

Within the context of plumbing systems, a high hazard is defined as:

Any condition, device or practice that, in connection with the water supply system, has the potential to cause death.

Because of this classification, these fixtures require appropriate backflow prevention measures when connected to the drinking water supply.

Backflow Prevention Requirements

Where a fixture is classified as a high hazard cross-connection, the drinking water supply must be protected by an appropriate backflow prevention device.

The suitability of backflow prevention devices for different hazard levels is outlined in Table 4.4.1 of AS/NZS 3500.1:2021.

^{Figure 1. Suitability of backflow prevention devices for different hazard levels (Source: AS/NZS 3500.1:2021, Table 4.4.1).}

As illustrated in Table 4.4.1, high hazard cross-connections require the use of approved backflow prevention devices capable of protecting the potable water system from contamination.

Depending on the installation configuration, suitable devices may include:

• Reduced Pressure Zone Devices (RPZD)
• Registered Air Gaps
• Atmospheric Vacuum Breakers
• Other approved devices appropriate to the level of hazard

All backflow prevention devices must be installed in accordance with the requirements of AS/NZS 3500.1:2021.

Installation Considerations

Where a high hazard backflow prevention device, such as a Reduced Pressure Zone Device (RPZD), is required to protect a bidet installation, careful consideration needs to be given to where the device is installed.

Under AS/NZS 3500.1:2021 (Clause 4.6.2.3), an RPZD should not be installed internally unless there is adequate provision for drainage. RPZD devices discharge water during normal operation and, if the valve fails, they can discharge large volumes of water continuously.

For this reason, installing an RPZD inside a bathroom or WC compartment in a Class 1 building is generally not recommended unless suitable drainage has been provided.

Another important point is that handheld bidet sprays must not be able to reach the toilet pan unless high hazard backflow protection is installed. If the spray can reach the pan, the installation is considered a high hazard cross-connection and must be protected in accordance with Table 4.4.1 above.

Bidettes must also hold WaterMark approval. If a bidette is installed without maintaining the required 25 mm air gap above the overflow level of the fixture, the installation must include an appropriate high hazard backflow prevention device, similar to the requirement for handheld bidet sprays.

Where an RPZD is installed, the device will generally need to be registered with the local council (fees may apply). The device must also be tested every 12 months by a licensed plumber holding a Backflow Prevention endorsement.

The same general requirements apply to bidet toilet seats (bidet douche seats). However, some products now available on the market include integrated backflow prevention devices. Because the number of models continues to grow, it is not practical to list all compliant products.

This makes it important for plumbers to carefully check the product certification and approved Scope of Use before installation.

Product Compliance

When selecting an aftermarket bidet toilet seat, always check the product labelling and certification details.

A common misconception is that if a product is labelled as WaterMark certified, it can automatically be installed without additional backflow protection. This is not necessarily correct.

WaterMark certification confirms that the product has been approved for use within the Australian plumbing regulatory framework. However, it does not automatically mean the product includes built-in backflow prevention.

A compliant WaterMark marking should include at least the following three pieces of information:

1. The WaterMark certification symbol
2. The WaterMark Technical Specification to which the product has been tested (for example WMTS-123)
3. The WaterMark licence number (for example Lic. 012345)

If these details are not present, the product should be checked carefully before installation.

Further information about WaterMark approvals can be found through the WaterMark Product Database.

Product Selection

When checking a specific brand or model of bidet toilet seat, plumbers should review the product listing within the WaterMark database.

In particular, check the Scope of Use section. This section may confirm whether the product includes an integrated backflow prevention device. For example, the product description may include wording similar to the following:

• Compliant with AS/NZS 2845.1:2022 High Hazard Atmospheric Vacuum Breaker (AVB) Backflow Prevention Device as per AS/NZS 3500.1:2021.

If this type of statement appears in the Scope of Use, the product may be installed without additional backflow protection, as the backflow device is already incorporated into the product.

If the WaterMark listing does not confirm integrated backflow protection, the installation will require an additional backflow prevention device suitable for the level of hazard.

In these cases, the device must be selected and installed in accordance with AS/NZS 3500.1:2021, and plumbers should refer to Table 4.4.1 above to determine the appropriate device for the installation.

Summary

Bidet toilet seats, bidettes and handheld bidet sprays are increasingly common fixtures in residential bathrooms, but their installation can introduce high hazard cross-connection risks.

Compliance with the Plumbing Code of Australia and AS/NZS 3500.1:2021 requires careful consideration of:

• hazard classification
• WaterMark certification
• appropriate backflow prevention
• correct installation practices

Plumbers should verify the WaterMark certification of the product, review the approved Scope of Use, and ensure appropriate backflow protection is installed where required.

Correct installation not only ensures compliance with regulatory requirements but also protects the integrity of the drinking water supply.

MPAQ members who have questions about this can call the MPAQ technical team on 07 3273 0800.