AS/NZS 3500 Plumbing and Drainage Standards Explained: Parts 1 to 4, Where NCC 2025 Calls Them Up and What Changed (2025 Guide)
AS/NZS 3500 is the plumbing and drainage Standard series: Part 1 water services, Part 2 sanitary plumbing and drainage, Part 3 stormwater drainage and Part 4 heated water services, with Part 0 as the glossary. What each Part covers, which edition is current, where NCC 2025 calls it up, and what changed in the 2025 editions clause by clause, with the free calculators that apply them.
AS/NZS 3500, often written AS 3500 or AS3500, is the Standard series Australian plumbing and drainage is designed and installed to. It comes in Parts: water services, sanitary plumbing and drainage, stormwater drainage and heated water services, with a glossary as Part 0. The current editions were published in 2025, and NCC 2025 calls them up.
This guide sets out what each Part covers, which edition is current, where the National Construction Code (NCC) calls each Part up, what changed in the 2025 editions clause by clause, and the free calculators that apply each Part.
In one minute
NCC 2025 references five Parts. Part 0 is the glossary, Part 1 water services, Part 2 sanitary plumbing and drainage, Part 3 stormwater drainage and Part 4 heated water services (Schedule of referenced documents; each Part's scope clause).
The 2025 editions are current. Parts 1 to 4 are fifth editions, published on 17 April 2025, and Part 3 was reissued in March 2026 with Amendment 1. Part 0 is the 2021 edition.
NCC 2025 calls up each Part by clause. Volume Three B1D3 (Part 1), C1D3 and C2D4 (Part 2) and B2D9 (Part 4); Volume One F1D3 and Volume Two H2D2 and H2D6 (Part 3).
Every flexible hose now has a class, and one that feeds a mixer valve, tap outlet or cistern has its own isolating valve. AS/NZS 3500.1 Clauses 2.3.2.2 and 5.4.2(l), and AS/NZS 3500.4 Clause 10.10.2(j).
Eaves gutter overflows and valley gutters changed. AS/NZS 3500.3 Section 3 and Appendix F, with Figure 3.6.2 corrected by Amendment 1.
1. The AS/NZS 3500 series, Part by Part
Standards Australia and Standards New Zealand publish the series jointly. Each Part serves both countries: in Australia it is read with the NCC, and in New Zealand with the New Zealand Building Code (Clause 1.2 of each Part).
A few provisions apply in one country only. Section 11 of Part 3, on rainwater harvesting, is for New Zealand (Clause 1.1(b)), and its Clause 5.3.8, on discharges from devices to stormwater, is headed "Australia only".
| Part | Title | What it covers | Where NCC 2025 calls it up | Free calculators |
|---|---|---|---|---|
| AS/NZS 3500.0:2021 | Glossary of terms | The common plumbing and drainage terms and definitions used across the series, product specifications and regulatory documents | Listed against A1G4 in Volumes One, Two and Three; in Volume Three a word Schedule 1 does not define takes its AS/NZS 3500.0 meaning (A1G4 Note) | None |
| AS/NZS 3500.1:2025 | Water services | Cold water and non-drinking water services, from the point of connection to the points of discharge: design, installation and commissioning | Volume Three B1D3, and clauses in Parts B3, B5, B6 and B7 (non-drinking water, cross-connection control, rainwater services and rainwater storage) | Water pipe size |
| AS/NZS 3500.2:2025 | Sanitary plumbing and drainage | Sanitary plumbing and drainage from the fixtures to a sewer, common effluent system or on-site wastewater management system | Volume Three C1D3 (sanitary plumbing) and C2D4 (sanitary drainage); swimming pool discharge in Volume One G1D5, Volume Two H2D2(2) and Volume Three C2D3 | None |
| AS/NZS 3500.3:2025, incorporating Amendment 1 | Stormwater drainage | Roof, surface and subsoil drainage to a point of connection: materials, design, installation and testing | Volume One F1D3 (Class 2 to 9); Volume Two H2D2 and H2D6 (Class 1 and 10); Volume Three E3D2 and E4D2 in Tasmania and Victoria | Eaves gutter and downpipe, gutter overflow, valley gutter, box gutter, stormwater pipe size and the rest |
| AS/NZS 3500.4:2025 | Heated water services | Heated water services from the valves on the cold water inlet to the downstream fixtures, including storage water heaters up to 700 L, heat exchange and instantaneous (continuous flow) water heaters | Volume Three B2D9, and B2D2, B2D6 to B2D8 and B2D11 | None |
Read down the call-up column and the split is clear. Parts 1, 2 and 4 are plumbing: Volume Three, the Plumbing Code of Australia, calls them up, and each one's preface says it gives Deemed-to-Satisfy solutions for that volume. Part 3 sits mainly with building work: Volume One calls it up for Class 2 to 9 buildings and Volume Two for Class 1 and 10 buildings (the building classes guide explains the split). Its preface aims at the NCC as a whole.
The free calculators apply the 2025 editions and show the clause behind every step. The water pipe size calculator runs Part 1's sizing method (Section 3 and Appendices C and D). The roof and stormwater drainage calculators run Part 3, from the roof catchment and the eaves, valley and box gutters to site stormwater pipes, pits and pump-outs. For a house outside Victoria, the Housing Provisions gutters and downpipes calculator runs the Part 7.4 tables instead.
2. Which edition is current
The current editions of Parts 1 to 4 are the 2025 editions. Each is a fifth edition, and each replaces the 2021 edition of the same Part (the preface of each). Standards Australia and Standards New Zealand published them on 17 April 2025.
Part 3 has one amendment. Amendment 1 is a correction amendment to Figure 3.6.2, the chart that sizes a valley gutter by design rainfall intensity and catchment area. It was published on 13 March 2026, and the Standard was reissued incorporating it (amendment control sheet). Refer to it as AS/NZS 3500.3:2025 incorporating Amendment 1.
Part 0, the glossary, was not revised in 2025. Its current edition is AS/NZS 3500.0:2021, the third edition.
NCC 2025 references these editions. Its Schedule of referenced documents, printed in each volume, lists Part 0 of 2021 and Parts 1 to 4 of 2025 against the clauses that call them up.
3. Where NCC 2025 calls up each Part, and is it mandatory
A Standard on its own is voluntary. Each 2025 Part says so on its "How to read this Standard" page: a Standard binds only where legislation or a contract calls it up. For building and plumbing work in Australia, the NCC does the calling up. Each call-up is a Deemed-to-Satisfy Provision, the clauses whose numbers carry a D:
Part 1, water services. Volume Three B1D3(1): "A cold water service must be in accordance with AS/NZS 3500.1."
Part 2, sanitary plumbing and drainage. Volume Three C1D3(1) for a sanitary plumbing system and C2D4(1) for a sanitary drainage system. A swimming pool's pumped discharge to the sanitary drainage system follows Part 2 too (Volume One G1D5, Volume Two H2D2(2), Volume Three C2D3).
Part 3, stormwater drainage. Volume One F1D3 for Class 2 to 9 buildings: "Stormwater drainage must be designed and constructed in accordance with AS/NZS 3500.3." For Class 1 and 10 buildings, Volume Two H2D2(1)(a) for drainage and H2D6(1)(a) for gutters and downpipes.
Part 4, heated water services. Volume Three B2D9(1): "A heated water service must be in accordance with AS/NZS 3500.4."
For houses, Volume Two offers table routes beside Part 3. The Housing Provisions Part 7.4 tables can size gutters and downpipes (H2D6(1)(b)), provided the roof drains to a stormwater system that complies with H2D2, and never for box gutters (H2D6(3)). Housing Provisions Part 3.3 can be used for roof drainage where the 5% AEP, 5-minute rainfall intensity is 255 mm/h or less, for sub-soil drainage and for land next to and under the building, provided the system otherwise complies with AS/NZS 3500.3 (H2D2(1)(b)). Where the Part 7.4 tables run out, at a type F gutter, the gutter is designed to AS/NZS 3500.3 (Table 7.4.3b). Victoria varies H2D6: there, gutters and downpipes follow AS/NZS 3500.3 only. The gutter and downpipe sizing guide walks through the Part 7.4 method.
Tasmania and Victoria also call up Part 3 for plumbing work, in stormwater Parts of their own inside Volume Three. TAS E3D2 and E4D2 accept AS/NZS 3500.3 or the Housing Provisions for roof drainage and for surface and subsurface drainage. VIC E3D2 calls up AS/NZS 3500.3 with SA HB 39 for roof drainage, AS/NZS 3500.3 prevailing where the two conflict, and VIC E4D2 calls up AS/NZS 3500.3 for surface drainage.
Several states vary the call-ups themselves, inside NCC 2025: B1D3 in New South Wales, Queensland, Tasmania and Victoria; B2D9 in New South Wales, South Australia and Western Australia; C1D3 in South Australia and Western Australia; and C2D4 in New South Wales, South Australia, Tasmania, Victoria and Western Australia. Some of these variations insert, replace or delete clauses of the Standard. Read your state's version of the clause before you rely on the Standard's own wording.
Following the Standard is one way to comply, not the only one. Under every call-up, the Performance Requirements can be met by a Deemed-to-Satisfy Solution, a Performance Solution or a combination of the two (A2G1). F1D3 says it outright: where stormwater drainage does not comply with it, a Performance Solution must show compliance with the relevant Performance Requirements.
The 2025 editions apply through NCC 2025 from the date each state and territory adopts it; the dates are in the NCC 2025 adoption guide.
4. What changed in the 2025 editions
Each Part's preface lists its major changes. Here are the ones that apply in Australia, by clause. The New Zealand-only changes, rainwater in Part 1 Section 16 and rainwater harvesting in Part 3 Section 11, are left out.
Part 1: Water services (AS/NZS 3500.1:2025)
Clause 2.3.2: flexible hose assemblies are now classified. Every flexible hose must be one of the four classes in Table 2.3.2.2, and the application fixes the class (Clause 2.3.2.2):
A connection between fixed points must be Class 2 (up to DN 20) or Class 3 (over DN 20 up to DN 32).
A hose with an integral stop valve or trigger must be Class 4.
A Class 1 hose, open-ended with no isolation after its inlet, must not be used under static pressure.
"Fixed points" means a rigid supply line to a fixture, fitting, valve, tap or appliance, or one supply line to another where the hose takes up expansion or movement (table note). Table 2.3.2.2 also sets a maximum operating pressure and a maximum length for each class. Hoses must suit their temperature, rated 70 °C ("L") or 90 °C ("H") (Clause 2.3.2.3), a submerged hose must be rated for submersion ("S") (Clause 2.3.2.4), and every hose must be in an accessible place and not buried (Clause 2.3.2.1).
Clause 5.4.2(l): an isolating valve immediately before each flexible hose connected to a mixer valve, tap outlet or cistern. It is the change most bathroom and kitchen rough-ins will show.
Clause 5.20: devices and appliances connected to the drinking water supply now have their own rules: pipes sized to Section 3, backflow protection to Section 4, an isolating valve to Clause 5.4, a pressure-limiting or pressure-reducing device where the device needs a lower pressure, and pipework that lets the device be disconnected and maintained.
Clauses 4.4 and 4.6: minor changes to the backflow prevention provisions for atmospheric vacuum breakers.
Clause 2.5.3 and Appendix I: new selection requirements for polyethylene pipe in the northern Australian regions Appendix I maps. The appendix covers PE pipes from DN 25 to DN 90 for cold drinking water where chlorine disinfection is used (Clause I.1).
Our free water pipe size calculator applies the 2025 edition's sizing method (Section 3 and Appendices C and D).
Part 2: Sanitary plumbing and drainage (AS/NZS 3500.2:2025)
Clause 13.24: installation requirements for waterless urinals, written to reduce the risk of struvite build-up. The undiluted discharge from a waterless urinal, for example, must not pass through copper pipework (Clause 13.24.2.3.1).
Clause 13.28: new provisions for connecting miscellaneous devices and appliances to sanitary plumbing and drainage.
Section 14: updated requirements for the main lines of a sanitary drainage system in a multi-unit development of 3 or more residential buildings (Clause 14.1). A note to Clause 14.1 counts each dwelling under a shared roof as a building.
Clause 16.2: polypropylene (PP) pipes and fittings added as an alternative for vacuum drainage systems.
Part 3: Stormwater drainage (AS/NZS 3500.3:2025)
Section 3 and Appendix F: updated requirements for residential eaves gutter overflows and valley gutters. Overflow measures are sized for the 1% AEP storm in Australia with every downpipe assumed blocked (Clause 3.5.3 and Table 3.3.4), by Appendix F for roof catchments up to 400 m² (Clause F.1). If your standard roof plumbing details predate 2025, this is the one to re-check. Our free eaves gutter overflow calculator runs Appendix F, and the Housing Provisions 7.4.4 to 7.4.7 route for a Class 1 or 10 building outside Victoria; the valley gutter calculator runs Clause 3.6.
Amendment 1 (13 March 2026): a correction amendment to Figure 3.6.2, the valley gutter chart. The Standard is now reissued incorporating it.
Clause 5.3.8 (Australia only): new requirements for devices and appliances that discharge water to the stormwater system. The discharge goes through a tundish or pit, in an accessible and visible place, with an air gap of at least 25 mm (Clause 5.3.8.2), and the stormwater system is sized for the maximum discharge (Clause 5.3.8.3).
Part 4: Heated water services (AS/NZS 3500.4:2025)
Clause 2.3: the same flexible hose classes and ratings as Part 1, applied to heated water (Clause 2.3.2.2).
Clause 10.10.2(j): an isolating valve immediately before each flexible hose connected to a mixer valve or tap outlet, mirroring Part 1. The clause sits in Section 10, which covers forced-circulation (flow and return) heated water reticulation limited to 65 °C (Clause 10.1).
5. What to update
Standard details and specifications. Add the isolating valve before every flexible hose to a mixer valve, tap outlet or cistern (AS/NZS 3500.1 Clause 5.4.2(l), AS/NZS 3500.4 Clause 10.10.2(j)). State the hose class required at each connection.
Product schedules. Specify flexible hoses by class and temperature rating, and "S" where a hose is submerged. Check each one on the WaterMark Product Database; Appendix B of Part 1 explains how WaterMark shows a product is fit for purpose.
Roof drainage. Re-run eaves gutter overflow checks against Section 3 and Appendix F of Part 3, and valley gutters against Figure 3.6.2 as Amendment 1 corrected it.
Devices that discharge water. Detail the tundish or pit and its 25 mm air gap where a device discharges to stormwater (AS/NZS 3500.3 Clause 5.3.8), and the backflow protection and isolating valve where one connects to drinking water (AS/NZS 3500.1 Clause 5.20).
Drawing title blocks. Name the edition the documentation is prepared to: AS/NZS 3500.1, 3500.2 and 3500.4:2025, and AS/NZS 3500.3:2025 incorporating Amendment 1.
State variations. Check your state's version of B1D3, B2D9, C1D3 and C2D4 before relying on the Standard's own wording (section 3).
Site briefings. The valve before each flexible hose to a mixer, tap outlet or cistern is the change crews will see at most rough-ins.
6. Where to read the source
The four Parts and the glossary are purchased from Standards Australia. The parts used here are AS/NZS 3500.1:2025 Clauses 1.1, 1.2, 2.3.2, 2.5.3, 4.4, 4.6, 5.4.2 and 5.20 and Appendices B and I; AS/NZS 3500.2:2025 Clauses 1.1, 13.24, 13.28, 14.1 and 16.2; AS/NZS 3500.3:2025 Clauses 1.1, 3.3.4, 3.5.3, 3.6 and 5.3.8, Appendix F and the amendment control sheet; AS/NZS 3500.4:2025 Clauses 1.1, 2.3.2, 10.1 and 10.10.2; the preface of each; and AS/NZS 3500.0:2021.
NCC 2025 is free to read on the NCC website: Volume Three A1G4, B1D3, B2D9, C1D3, C2D3 and C2D4 and the Tasmanian and Victorian E3D2 and E4D2; Volume One F1D3 and G1D5; Volume Two H2D2 and H2D6; Housing Provisions Parts 3.3 and 7.4; and the Schedule of referenced documents.
Sources: AS/NZS 3500.0:2021, AS/NZS 3500.1, 3500.2, 3500.3 (incorporating Amendment 1) and 3500.4:2025, Standards Australia; NCC 2025 Volumes One, Two and Three and the Housing Provisions; Standards New Zealand (publication dates). First published 6 May 2025; rewritten 14 October 2026 as a guide to the whole series.
Inside AEC Assistant the Code text is searchable by clause, and on a paid plan the Standards are too. Ask which Parts of AS/NZS 3500 apply to your project and where NCC 2025 calls them up in your state, and the answer comes back with the clause it was read from.
This article is general guidance. The building surveyor or certifier for your project determines compliance.
Questions this guide answers
What is AS/NZS 3500?
AS/NZS 3500, often written AS 3500, is the joint Australian and New Zealand Standard series for plumbing and drainage. Part 1 covers water services, Part 2 sanitary plumbing and drainage, Part 3 stormwater drainage and Part 4 heated water services, and Part 0 is the glossary of terms. In Australia, NCC 2025 calls up Parts 1 to 4 as the Deemed-to-Satisfy way to meet its plumbing and drainage requirements.
What do AS/NZS 3500.1, 3500.2, 3500.3 and 3500.4 cover?
AS/NZS 3500.1 covers cold water and non-drinking water services from the point of connection to the points of discharge. AS/NZS 3500.2 covers sanitary plumbing and drainage from the fixtures to a sewer, common effluent system or on-site wastewater management system. AS/NZS 3500.3 covers roof, surface and subsoil drainage to a point of connection. AS/NZS 3500.4 covers heated water services, including storage water heaters up to 700 L, heat exchange water heaters and instantaneous water heaters.
Which edition of AS/NZS 3500 is current?
The 2025 editions of Parts 1 to 4, each a fifth edition, published by Standards Australia on 17 April 2025. AS/NZS 3500.3:2025 was reissued in March 2026 incorporating Amendment 1, a correction to Figure 3.6.2, the valley gutter chart. Part 0, the glossary, is the 2021 edition. These are the editions NCC 2025 lists in its Schedule of referenced documents.
Is AS/NZS 3500 mandatory, and where does the NCC call it up?
A Standard is voluntary until legislation or a contract calls it up. NCC 2025 calls up Part 1 in Volume Three B1D3, Part 2 in C1D3 and C2D4, Part 4 in B2D9, and Part 3 in Volume One F1D3 for Class 2 to 9 buildings and Volume Two H2D2 and H2D6 for Class 1 and 10 buildings. Following the Standard is the Deemed-to-Satisfy route; a Performance Solution is the alternative. When NCC 2025 applies depends on the date your state or territory adopts it.
What changed in AS/NZS 3500:2025?
Part 1 sorts flexible hoses into four classes (Clause 2.3), requires an isolating valve immediately before each flexible hose to a mixer valve, tap outlet or cistern (Clause 5.4.2) and adds rules for devices connected to the drinking water supply (Clause 5.20). Part 2 adds waterless urinal (Clause 13.24) and miscellaneous discharge (Clause 13.28) rules and updates multi-unit developments (Section 14). Part 3 updates eaves gutter overflows and valley gutters (Section 3 and Appendix F) and adds device discharges to stormwater (Clause 5.3.8). Part 4 applies the hose classes to heated water (Clause 2.3), and the isolating valve to circulating heated water systems (Clause 10.10.2).
What are the flexible hose classes in AS/NZS 3500.1:2025?
Clause 2.3.2.2 sets four classes. Class 1 is an open-ended hose with no isolation after its inlet and must not be used under static pressure, Class 2 is a connector up to DN 20 and Class 3 a connector over DN 20 up to DN 32 between fixed points, and Class 4 is a hose with its own stop valve or trigger. Hoses are also rated 70 °C (L) or 90 °C (H), and S for submersion.
