This article is published to alert plumbing and building industry stakeholders in Western Australia of changes to current regulations and standards affecting plumbing system design and installation in WA.

The Plumbers Licensing and Plumbing Standards Regulations 2000 (Plumbing Regulations) have been amended to align with the latest version of the Plumbing Code of Australia (PCA 2022) which takes effect on 1 May 2023.

In turn, the PCA 2022 calls up the 2021 version of the AS/NZS 3500 Plumbing and drainage series also taking effect on 1 May 2023. AS/NZS 3500:2021 Parts 1, 2 and 4 will replace the 2018 versions of these standards.

Regulation 49 of the Plumbing Regulations modifies certain deemed-to-satisfy (DTS) provisions in the PCA 2022 and referenced DTS standards, AS/NZS 3500:2021 to ensure continued compatibility with WA specific conditions.

Reflux valves and fixture traps

Regulation 49 of the Plumbing Regulations has been amended to:

1. modify AS/NZS 3500.2:2021, clause 4.5.3 to allow reflux valves in drainage plumbing systems to be installed upstream of a boundary trap.
   This provides a practical installation solution, when a reflux valve is required and a boundary trap is already in place as part of the water service provider’s infrastructure, for example the Water Corporation. 
    
2. modify AS/NZS 3500.2:2021, clause 6.5.1 to require fixture traps buried in the ground or embedded in concrete below sanitary fixtures, to not be of a larger diameter than the fixture outlet itself.
   This avoids oversized traps being embedded under a fixture. Oversized fixture traps are not self-cleansing, nor easily maintained when installed in an inaccessible location such as under a bath or shower. See diagram below.     

Junctions in sanitary and drainage plumbing systems

New clauses 4.9.1.2 and 6.6.2.4.2 have been inserted into AS/NZS 3500.2:2021, requiring all junctions in sanitary and drainage plumbing systems used to connect DN 100 drains to each other on grade to be elevated at a minimum incline of 15 degrees.

These provisions are for new installations only and have been inserted to compensate for the reduction in flows in sanitary and drainage plumbing systems. Consideration will need to be given to ensure there is adequate height allowance in building design, to cater for the increased vertical height that will be required for sanitary and drainage plumbing systems. See diagram below.

This diagram shows the additional vertical space that may be required for sanitary plumbing pipes as well as the requirements for fixture connections in slab on ground construction.

Consequences of the changes

The above changes are part of a larger suite of reforms to the Plumbing Regulations, the PCA 2022 and AS/NZS 3500:2021 commencing on 1 May 2023.

These particular changes are being highlighted at an early stage as they may require consideration by all parties involved in plumbing and building design to ensure that plumbing installations are compliant.

Industry bulletins on the general changes to the Plumbing Regulations and the PCA will be released in the coming months.