Plumbing and drainage joint standards get an overhaul

Calling all plumbers, drainlayers, building designers, consenting officers, and other construction industry professionals – the 2025 editions of the AS/NZS 3500 Plumbing and drainage series of standards are now available from the webshop. These revisions include some major changes and improvements to clarify some installation provisions and remove inconsistencies. The series includes: Part 0: Glossary of terms, Part 1: Water services, Part 2: Sanitary plumbing and drainage, Part 3: Stormwater drainage, Part 4: Heated water services.

Joint standards support tradespeople across Australasia

The publication of the 2025 AS/NZS 3500 series follows a three-yearly revision project to continuously improve these standards. These standards play an integral part in setting out design and installation requirements for plumbing and drainage systems both in New Zealand and in Australia. They also support the Trans-Tasman Mutual Recognition Arrangement, which provides for plumbers, and drainlayers who are registered in New Zealand to practice in Australia, and vice versa.

‘It puts everyone on the same page’, says Ross Wakefield, Senior Plumbing and Hydraulic Services Engineer with Building Performance, MBIE who have sponsored New Zealand’s participation in this project. ‘Users of the standards are encouraged to familiarise themselves with the changes, before these are proposed to be referenced as means of complying with the New Zealand Building Code, replacing 3500:2021 editions. There will be an opportunity to have your say beforehand as part of a future  Building Code update consultation.’

Thank you to all those who have contributed to the revision of these standards, including through Standards Australia’s public consultation process in 2023. Experts representing New Zealand’s input into this project have come from Master Plumbers New Zealand,  Plastics, Plumbers, Gasfitters and Drainlayers Board, Plumbing Distributors Association of New Zealand, Water New Zealand, Association of Hydraulic Services Consultants Australia and New Zealand, , Chartered Institution of Building Services Engineers ANZ, and the Ministry of Business, Innovation and Employment (MBIE).

Get your copy today

The AS/NZS 3500 series of standards are available on Standards New Zealand's website:

Get standards(external link)

These can be viewed for free by licensed plumbers, gasfitters and drainlayers through their trade login on the Plumbers, Gasfitters and Drainlayers Boards website.

In the meantime…

It is important to note that the previous 2018 editions of AS/NZS 3500:2018 currently remain in force as acceptable solutions for compliance with Building Code clauses E1 Surface Water, G12 Water Supplies and G13 Foul Water, subject to some modifications.

MBIE will consult on referencing the 2025 edition of AS/NZS 3500 as an acceptable solution in a future Building Code update, and encourage you to stay up to date with proposed Building Code changes by subscribing to updates:

Subscribe to updates - Building performance(external link)

Note: If you wish to use the AS/NZS 3500:2025 standards before they are referenced as acceptable solutions, you need to propose this as an alternative solution to the relevant building consent authority when applying for a building consent.

For more information on using alternative solutions for compliance with the Building Code, please refer to:

Alternative solutions for compliance with the Building Code - Building performance(external link)

So what’s different?

Major changes within the AS/NZS 3500: 2025 Plumbing and drainage series include:

• Flexible hoses: New requirements specifying the use of certain classes of flexible hose assemblies in cold water applications (see AS/NZS 3500.1:2025 Part 1 Clause 2.3 and Part 4 Clause 2.3)
• Isolation valves: New requirement for an isolating valve to be installed immediately before each flexible hose assembly that is connected to a mixer valve, tap outlet or cistern (see AS/NZS 3500.1:2025 Part 1 Clause 5.4.2 and Part 4 Clause 10.10.2)
• Backflow prevention: Minor changes to the backflow prevention provisions for atmospheric vacuum breakers (see AS/NZS 3500:2025 Part 1, Clause 4.4 and 4.6)
• Rainwater harvesting systems: New requirements for rainwater tanks and rainwater supply systems in New Zealand, including charged rainwater harvesting systems (see AS/NZS 3500:2025 Part 1 Section 16 and Part 3 Section 11)
• Waterless urinals: New requirements for the installation of waterless urinals to reduce the risk of struvite build up and blockages in the sanitary drainage system (see AS/NZS 3500:2025 Part 2 Clause 13.24)
• Multi-unit building developments: Updated requirements for sanitary drainage on multi-building development sites where there's more than one building connected to a sanitary drain within a single property (see AS/NZS 3500:2025 Part 2 Section 14)

Note: G13/AS3 currently excludes the AS/NZS 3500.2:2021 Section 14 Multi-unit development provisions from this Acceptable Solution

• Miscellaneous appliances: New requirements for the connection of miscellaneous water using devices and appliances to a drinking water supply and sanitary drainage system (see AS/NZS 3500:2025 Part 1 Clause 5.20 and Part 2 Clause 13.28)

Note: The AS/NZS 3500:2025 Part 3 requirements for the connection of miscellaneous devices and appliances to stormwater drainage systems do not apply for New Zealand

• Vacuum drainage: Polypropylene pipes and fittings included as an alternative product material for vacuum drainage systems (see AS/NZS 3500:2025 Part 2 Clause 16.2)