Published 17 April 2025 – mandatory from 20 October 2025

Australia’s plumbing playbook just had a major rewrite.
Standards Australia has released new 2025 editions of the entire AS/NZS 3500 plumbing & drainage series:

Part 1 – Water Services
Part 2 – Sanitary Plumbing and Drainage
Part 3 – Stormwater Drainage
Part 4 – Heated Water Services

Because these standards are referenced by the Plumbing Code of Australia (PCA) and Victoria’s Plumbing Regulations 2018, every practitioner has a six‑month transition window. After 20 October 2025, only the 2025 editions will be accepted for new plumbing work.

Table 2.3.2.2 Flexible hose assembly classification

Class	Description	Application	Maximum operating pressure	Maximum length
1	End of line hoses with an open end	Hoses which have no isolation device after inlet. Not intended for use under static pressure	< 250 kPa (dynamic)	10 m
2	Flexible connectors up to and including DN 20	Connections between fixed points	1 400 kPa (static)	2 m
3	Flexible connectors > DN 20 and ≤ DN 32	Connections between fixed points	25 mm = 1 400 kPa 32 mm = 1 350 kPa (static)	10 m
4	End of line hoses with shut-off devices, pressurized	Hoses for wash down tapware or which have isolation after the inlet of the hose	1 400 kPa (static)	10 m < DN 25 2 m for ≥ DN 25

NOTE For this clause, fixed points are either between rigid supply lines and a fixture, fitting, valve, tap, appliance or similar; or between supply line to supply line to allow for expansion or movement.

Part 1 – Water Services (AS/NZS 3500.1:2025)

Clause 2.3 – Flexible‑hose assemblies must now meet class‑specific ratings aligned with AS 3499:2022 → fewer burst‑hose failures.
Clauses 4.4 & 4.6 – Backflow provisions for atmospheric vacuum breakers refined → more reliable potable‑water protection.
Clause 5.4.2 – New mandatory isolating valve immediately upstream of every flexible hose → quicker maintenance and emergency shut‑off.
Clause 5.20 – Clear rules for connecting “miscellaneous devices” (fridge ice‑makers, bidets, etc.) → eliminates approval grey areas.

Part 2 – Sanitary Plumbing & Drainage (AS/NZS 3500.2:2025)

Clause 13.24 – Stricter installation rules for waterless urinals to curb struvite build‑up → longer service life and improved hygiene.
Clause 13.28 – Definitions for connecting “miscellaneous sanitary devices” (e.g. macerators) → faster inspector sign‑off.
Section 14 – Main‑drain sizing rewritten for multi‑unit (≥3‑dwelling) projects → suits modern high‑density housing.
General – UV‑exposure limits and jointing clarifications for plastic pipework → prevents premature failures.

Part 3 – Stormwater Drainage (AS/NZS 3500.3:2025)

Section 3 – Eaves‑gutter overflow and valley‑gutter sizing rules overhauled → better resilience in intense rainfall.
Clause 5.3.8 – Sets conditions for discharging devices (e.g. heat‑pump bleed) to stormwater → clarifies compliance grey areas.
Appendix F – Overflow design for eaves gutters upgraded from informative to mandatory → enforces safer detailing nationwide.

Part 4 – Heated Water Services (AS/NZS 3500.4:2025)

Clause 2.3 – Mirrors Part 1 hose‑class rules for hot lines → prevents delamination and scald risk.
Clause 10.10.2 – Isolation valve now compulsory before every hot‑water flexi hose → aligns hot & cold maintenance practice.
System design – Circulating‑hot‑water sizing and TMV placement clarified → improves energy efficiency and Legionella control.

Compliance Timeline

Now → 19 Oct 2025 – Either the 2021 or 2025 editions may be used.
From 20 Oct 2025 – Only the 2025 editions are deemed‑to‑satisfy under the PCA and Plumbing Regulations 2018.

Practical Next Steps

Audit your standard details for the new valve and hose notes.
Re‑run eaves‑gutter calculations using Appendix F (Part 3).
Update product schedules so all flexi hoses meet AS 3499 class ratings.
Brief site crews on new isolation‑valve locations to avoid costly re‑work.
Book CPD – look out for VBA webinars & technical bulletins on the 2025 rollout.

Need Instant Clause Checks?

Ask AEC Assistant anything about the 2025 AS/NZS 3500 series—valve placement, overflow calculations, material selections—and get authoritative answers in seconds: aecassistant.ai.

Written by Andrew Galea, Vove Architects & AEC Assistant – helping Australian practitioners stay on code since 2025.

AS/NZS 3500: 2025 – What’s Changed and How to Get Ready

Part 1 – Water Services (AS/NZS 3500.1:2025)

Part 2 – Sanitary Plumbing & Drainage (AS/NZS 3500.2:2025)

Part 3 – Stormwater Drainage (AS/NZS 3500.3:2025)

Part 4 – Heated Water Services (AS/NZS 3500.4:2025)