The AS/NZS 3500 series is the key set of standards for plumbing and drainage systems across Australia and New Zealand.

Standards Australia recently hosted a live event that discussed changes to these standards. Led by Tom Roberts, Committee Member of Joint Australian/New Zealand Technical Committee WS-014, Plumbing and Drainage, the event delved into the significant changes of the 2021 edition that impact professionals' work and compliance. It also gave insights into proposed changes to the AS/NZS 3500 standards series for NCC 2025.

The event also included a live Q&A session, allowing attendees to ask Mr. Roberts questions related to the standards and their work.

Read on for the answers to all the questions from the event and view the video recording at the bottom of this page.

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Dead Legs

Does the 2 litre limit for heated water dead legs apply to all building classes?

Answer: AS/NZS 35004:2021 Section 10 applies to circulatory heated water systems (limited to 65oC in all building types) in all building classifications. Clause 10.9.3.2 outlines requirements to minimise the length and capacity of dead legs. Notes within this clause recommend that dead legs with volumetric capacity exceeding 2 L should be avoided or require additional considerations. AS/NZS 3500.4:2021 Appendix Q provides guidance for estimating wait times for the delivery of heated water using internal diameters and volumes of heated water pipes.

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Heated water metres

Are the provisions relating to heated water meters being located as close as practicable to the area that they serve as mandatory (normative) or guidance (informative)?

Answer: AS/NZS 3500.2:2021 Section 10 applies to heated water circulatory systems. Within this section, Clause 10.9.3.1 requires a heated water meter servicing a single apartment to be located in the common area of the property and accessible to the apartment owner. Clause 10.9.3.2 states that the heated water metre must be installed as close as practicable to the apartment to help reduce energy losses. This is a normative requirement; however, the exact distance will depend on the design of the building.  

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Cold water meters

When amending the provisions in AS/NZS 3500.4:2021, was consideration given to including requirements for the location of cold water meters?

Answer: The location of a cold water meter is generally determined by the Network Utility Operator and in most jurisdictions falls outside of the scope of AS/NZS 3500.1.

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Drains in unstable sites

Is a Performance Solution required for each sanitary drainage installation in reactive sites?

Answer: AS/NZS 3500.2:2021 provides one of many solutions for installing sanitary drainage systems in sites with unstable soils. AS/NZS 3500.2 Appendix G provides guidance on how to install products intended to reduce the risk of soil or ground movement effecting the sanitary drainage system. As this appendix is informative, it can be used to inform a Performance Solution in accordance with the Plumbing Code of Australia or New Zealand Building Code. Consultation with your local plumbing regulatory authority and a suitably qualified expert is recommended to ensure the sanitary drainage solution is appropriate to the specific site soil classification and characteristics.  

Do the requirements for drains in unstable sites also apply to stormwater systems?

Answer: AS/NZS 3500.3:2021 currently does not contain specific provisions for stormwater systems installed in sites with unstable soils.

Are there any other solutions for sanitary drainage systems in sites with unstable soils, other than AS/NZS 3500.2:2021 Appendix G?

Answer: There are other solutions for sanitary drainage systems in sites with unstable soils, and a suitable qualified expert should be consulted to ensure that the sanitary drainage solution is appropriate to the specific site soil classification and characteristics.  

Is a licensed plumber suitably qualified to determine the appropriate sanitary drainage solution for sites with unstable soils?

Answer: Consultation with your local plumbing regulatory authority and a suitably qualified expert is recommended to ensure the sanitary drainage solution is appropriate to the specific site soil classification and characteristics.  

Does AS/NZS 3500.2 contain guidance for sanitary drainage systems in for mine subsidence areas?

Answer: AS/NZS 3500.2:2021 Clause 5.6 Drains in other than stable ground, states that methods of support and bedding shall be designed to withstand and suit the ground conditions. This clause includes a note which advises that in proclaimed mine subsidence or landslip districts, the appropriate authority should be referred to for advice on the subsidence or landslip parameters for the sanitary drainage system.

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Separation distances

Are the separation distances between building services considered adequate?

Answer: Consultation between the committees responsible for AS/NZS 3500 Plumbing and drainage, AS 3000 Electrical installations and AS/NZS 5601.1 Gas installation has resulted in agreed and consistent separation distances across all three building service standards.

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Junctions

Does the requirement to incline junctions in sanitary drainage installations only apply to new installations?

Answer: AS/NZS 3500.2:2021 Clause 4.9.1.2 is for new installation. This clause requires junctions used to make connections of a DN 100 branch drain to another DN 100 drain have an inclination of not less than 15o. Clause 4.9.1.3 outlines scenarios where the entry of a branch drain may be on grade, however a note recommends that where there is sufficient height available, junctions should also be inclined 15o in existing installation to reduce the risk of blockages.

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Plastic pipes

Are the changes in relation to polyethylene pipework in relation to water service or drainage systems?

Answer: The amendment to AS/NZS 3500.1:2021 Clause 5.2 Installation of pipes and fittings, has ensured clarity in the references to plastic pipework installation standards. The secondary standards referenced include AS/NZS 2033 for PE, AS/NZS 2032 for PVC, and AS/NZS 3690 for ABS.

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Flexible hoses

What are the key amendments in regards to flexible hoses?

Answer: The public comment draft for AS/NZS 3500.1 and AS/NZS 3500.4 is currently open for public review and contain changes relating to flexible hoses. The plumbing industry isare encouraged to review these proposed changes and comment.

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During the webinar there were also several questions relating to future revision topics. Some suggestions include pipe sizing updates, fire-fighting sprinkler systems in residential buildings, and changes to the access requirements of plumbing and drainage systems.

All are great ideas and Standards Australia encourages anyone with suggestions for future amendments to AS/NZS 3500 series to submit a proposal for change here: Submitting a Proposal

Live Event Recording: Changes to AS/NZS 3500 Plumbing and Drainage Standards

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The AS/NZS 3500 Plumbing and Drainage standards are available via the Standards Australia Store and our distribution partners.

NOTE: This webinar and other information on this page contains general information and is not formal advice. Users must make their own assessment as to the suitability of this material and the standards referred to herein for their specific business needs.