AS/NZS 3500: Plumbing and drainage standard for residential builders
AS/NZS 3500 is Australia's plumbing and drainage standard. Parts 1-4 cover water, sanitary, stormwater and heated water. NCC Volume 3 calls it up as DTS.
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AS/NZS 3500 is the joint Australian and New Zealand standard for plumbing and drainage. It comes in four substantive parts: water services (Part 1), sanitary plumbing and drainage (Part 2), stormwater drainage (Part 3), and heated water services (Part 4). The 2025 edition was published 17 April 2025 and applies to all work commenced on or after 20 October 2025 (verified 2026-05-08, Standards Australia). The NCC calls it up in Volume Three (Plumbing Code of Australia) as the primary deemed-to-satisfy (DTS) path for plumbing compliance. Builders don’t read the standard, their licensed plumber does, but builders sign off the project and need the plumber’s Certificate of Compliance (CoC) before occupancy. The most common site failure: heated water outlets above 50 degrees Celsius at sanitary fixtures, a non-negotiable under Part 4.
In plain English
AS/NZS 3500 sets minimum requirements for the design, installation, commissioning, and testing of plumbing and drainage systems in Australian and New Zealand buildings. For residential builders, it governs everything from the cold-water tap at the kitchen bench to the sanitary sewer connection at the boundary and the stormwater line to the kerb.
The standard operates as a joint publication: Standards Australia and Standards New Zealand maintain it together. The Australian version is adopted by reference into state plumbing legislation across all eight states and territories.
The NCC Volume Three (Plumbing Code of Australia) is the regulatory document. AS/NZS 3500 sits inside it as the primary DTS path. Using AS/NZS 3500 means the plumbing work is taken to comply with the NCC’s Performance Requirements without needing a separate performance solution (verified 2026-05-08, NCC ABCB).
Builders don’t engage with AS/NZS 3500 directly. Their licensed plumber is responsible for design, installation, and the final Certificate of Compliance. The builder’s job is to:
- Confirm the plumber holds the correct state licence before work starts
- Ensure the CoC is issued and on file before the Occupation Certificate (OC) or Final Inspection
- Coordinate plumbing sequencing (first fix before frames are closed, second fix after finishing) to avoid costly rework
The parts and what they cover
Part 0: Glossary of terms
AS/NZS 3500.0 defines terms used across the series. NCC Volume Three states that where a word is not defined in Schedule 1 of the NCC, the meaning from AS/NZS 3500.0 applies. Not a technical standard in itself: a reference layer for the whole series.
Part 1: Water services
AS/NZS 3500.1 covers the design and installation of cold water services from the point of connection (typically the water meter or boundary of a lot) to every outlet inside and outside the building. Also covers non-drinking water services (rainwater, recycled/third-pipe) from point of connection to points of use.
Key requirements that affect residential builders on site:
| Requirement | Rule |
|---|---|
| Static pressure | Maximum 500 kPa at any outlet (regulator required if supply pressure exceeds this) |
| Flow rate | Minimum flow rates set per fixture type |
| Backflow prevention | Devices required based on hazard class of the connection (air gaps, check valves, RPZ valves) |
| Flexible hoses | 2025 update: new provisions aligned with AS 3499:2022 to reduce connector failure risk |
| Pipe identification | Cold water pipes must be identifiable throughout the installation |
The 2025 edition of Part 1 included new deemed-to-satisfy provisions for appliances and devices, and expanded requirements for backflow prevention on high-hazard fixtures (verified 2026-05-08, Standards Australia AS/NZS 3500 spotlight).
Part 2: Sanitary plumbing and drainage
AS/NZS 3500.2 covers the design and installation of sanitary drainage systems from fixtures to a sewer, common effluent system, or on-site wastewater management system. This is the most complex part for a typical residential build.
Scope includes:
- WC pans, cisterns, basins, baths, showers, laundry troughs, kitchen sinks
- Waste pipes, soil pipes, vent pipes, inspection openings, traps
- Drain installation: depth, falls, material, testing
- On-site wastewater management where a sewer connection is not available
Key requirements:
| Item | Rule |
|---|---|
| Minimum drain fall | Generally 1.65% (1:60) for DN100 sanitary drains; specific falls set per pipe diameter and material |
| Trap seal depth | Trap seals required on every fixture to prevent sewer gas entry |
| Vent pipes | Sanitary stacks must be vented to atmosphere to maintain trap seals |
| Pipe materials | Unapproved substitutions are a common defect inspection find |
| Testing | System must be pressure or water tested before being concealed |
The 2025 edition clarified sanitary drain requirements for multi-building developments, relevant on medium-density residential sites (verified 2026-05-08, Standards Australia AS/NZS 3500 spotlight).
Part 3: Stormwater drainage
AS/NZS 3500.3 governs roof drainage (gutters, downpipes), surface drainage (paved areas, subsoil), and the connection to a point of discharge such as the kerb, channel, or an approved absorption system.
Key requirements for residential builds:
| Item | Rule |
|---|---|
| Roof drainage sizing | Gutter and downpipe sizes determined by design rainfall intensity for the location (Bureau of Meteorology data used) |
| Valley gutters | 2025 update introduced clearer rules for eaves gutters and valley gutters |
| Eaves gutters | Minimum falls and overflow provision required |
| Subsoil drainage | Drainage of subfloor spaces required where moisture risk is present |
| Point of discharge | Connection to kerb, channel, or approved system required; cannot discharge to neighbouring properties or overland without approval |
Part 4: Heated water services
AS/NZS 3500.4 covers hot water systems from the heater to every outlet. The critical builder-facing requirement is the 50 degree Celsius cap on water temperature at sanitary fixtures used primarily for personal hygiene (showers, baths, basins).
The standard requires a tempering valve or thermostatic mixing valve (TMV) complying with AS 4032.2, set to deliver a maximum of 50 degrees Celsius at each outlet supplied from the device. To achieve 50 degrees Celsius at the outlet, the storage or delivery temperature at the valve must be at least 60 degrees Celsius (the 10 degree differential requirement for valve operation) (verified 2026-05-08, VBA AS/NZS 3500.4 changes).
The conflict (store hot to kill Legionella, deliver warm to prevent scalding) is resolved by the tempering valve: the storage system sits at 60 degrees Celsius or above; the TMV blends down to 50 degrees Celsius at the fixture.
The 2025 edition updated flexible hose provisions for heated water services, aligned with AS 3499:2022 (verified 2026-05-08, Standards Australia AS/NZS 3500 spotlight).
What it doesn’t cover
AS/NZS 3500 does not cover:
- Gas installations: these fall under AS/NZS 5601
- Fire protection plumbing (sprinklers, hydrants, hose reels): separate standards and licence categories apply
- Swimming pools and spas: pool water circulation and treatment sit under separate AS standards
- Industrial and commercial process plumbing in Class 5-8 buildings beyond basic water and sanitary services
- Recycled water systems design requirements beyond connection point: water utility rules govern those
Current edition: 2025
The 2025 edition (Parts 0-4) was published on 17 April 2025, replacing the 2021 edition. The transition deadline: all plumbing work commenced on or after 20 October 2025 must comply with the 2025 version (verified 2026-05-08, Standards Australia spotlight; VBA updated standards page).
Key changes in the 2025 edition:
- Flexible hoses: new provisions aligned with AS 3499:2022 to reduce connector failure risk
- Atmospheric vacuum breakers elevated to high-hazard testable devices for backflow protection
- New deemed-to-satisfy provisions for appliances and devices
- Sanitary drain requirements clarified for multi-building developments
- Polyethylene pipe installation requirements updated for high-pressure conditions in northern Australia
- Clearer rules for eaves and valley gutters
- Waterless urinal requirements added
- Polypropylene pipes permitted for vacuum drainage systems
- Rainwater harvesting provisions added for New Zealand
Practical implications
Licensing: who must hold what
All plumbing and drainage work on a residential site must be performed or supervised by a licensed plumber. State licensing terminology differs:
| State | Licence / registration | Regulator |
|---|---|---|
| NSW | Contractor licence + Qualified Supervisor Certificate, or Tradesperson Certificate (no cost threshold: licence required regardless of job size) | NSW Fair Trading (verified 2026-05-08, nsw.gov.au) |
| VIC | Plumbing registration (various classes: domestic plumbing, water supply, sanitary, drainer, gasfitter, mechanical services, fire protection) | Building and Plumbing Commission (formerly VBA) (verified 2026-05-08, vba.vic.gov.au) |
| QLD | Plumbing and Drainage contractor licence + occupational licence | QBCC (verified 2026-05-08, qbcc.qld.gov.au) |
| TAS | Plumbing practitioner licence (WSDR: Water, Sanitary, Drainage and Roof streams) + contractor licence | Consumer, Building and Occupational Services (CBOS) (verified 2026-05-08, cbos.tas.gov.au) |
| WA, SA, NT, ACT | Licensing required in all states and territories; confirm current licence classes and regulator with the relevant state building or plumbing authority before engaging | State/territory building regulator |
Unlicensed plumbing work is a breach of state legislation. In NSW, penalties for unlicensed plumbing work are up to $22,000 for individuals and $110,000 for companies (verified 2026-05-08, NSW Fair Trading).
Sequencing on a residential build
Plumbing sits in two distinct stages on a residential job:
First fix (rough-in):
- Sewer drain laid to invert levels and falls before slab pour (or under suspended floor before sub-floor is enclosed)
- Stormwater drain laid
- Sanitary stack rough-in inside the frame
- Cold water rough-in (copper or CPVC/PEX runs to fixture locations)
- Hot water rough-in
- Inspection by plumber before frames are closed or slab is poured; often a notifiable inspection under state plumbing regulations
Second fix (fitoff):
- Hot water unit installed and connected
- Tempering valve or TMV set to 50 degrees Celsius max
- Fixtures installed (WCs, basins, bath, shower, taps)
- Final pressure test
- Certificate of Compliance issued by the licensed plumber
The CoC is a hard gate for the OC and building permit sign-off. No CoC means the plumbing cannot be legally used.
Certificate of Compliance state names
| State | Document name |
|---|---|
| NSW | Certificate of Compliance (Plumbing and Drainage) |
| VIC | Certificate of Compliance (Plumbing) |
| QLD | Compliance Certificate (Hydraulic Services) |
| WA | Certificate of Compliance |
| SA | Certificate of Occupancy (plumbing component) |
| TAS | Certificate of Compliance |
| NT | Inspection report / CoC (verify with NT Building Advisory Services) |
| ACT | Certificate of Compliance |
Common defects and compliance failures
| Defect | Cause |
|---|---|
| Hot water above 50 degrees Celsius at outlet | Tempering valve not installed, failed, or set incorrectly |
| Poor or missing vent | Sanitary drain not vented; trap siphonage causes sewer gas entry |
| Inadequate drain falls | Sanitary drain installed flat; solids accumulate and block |
| Flexible hose failures | Braided flexible hoses at under-bench connections corrode or burst; now specifically addressed in AS/NZS 3500.1:2025 |
| Substandard materials | Unapproved pipe materials or fittings used, revealed at inspection |
| Missing inspection openings | Drain not accessible for clearing blockages |
| Stormwater to sewer cross-connection | Downpipes connected to sanitary drain instead of stormwater; overloads sewerage system |
Source link
AS/NZS 3500 series is paywalled. The Standards Australia store lists each part: Standards Australia AS/NZS 3500 (search “3500 plumbing”). The NCC Volume Three (Plumbing Code of Australia), which incorporates AS/NZS 3500 as DTS, is free at ncc.abcb.gov.au (verified 2026-05-08).
References
- Standards Australia, Spotlight on: AS/NZS 3500 Plumbing and Drainage Standards Series, 2025 Updates. https://www.standards.org.au/blog/spotlight-on-as-nzs-3500 (verified 2026-05-08).
- Victorian Building Authority (Building and Plumbing Commission), Updated plumbing and drainage standards (AS/NZS 3500 series). https://www.vba.vic.gov.au/plumbing/plumbing-regulatory-framework/updated-plumbing-and-drainage-standards-asnzs-3500-series (verified 2026-05-08).
- Victorian Building Authority (Building and Plumbing Commission), NCC 2025 Volume Three Plumbing Code of Australia. https://www.vba.vic.gov.au/plumbing/plumbing-regulatory-framework/ncc-2025-volume-3-plumbing-code-of-australia (verified 2026-05-08).
- Australian Building Codes Board, NCC 2022 Volume Three, Plumbing Code of Australia. https://ncc.abcb.gov.au/editions/ncc-2022/adopted/volume-three (verified 2026-05-08).
- NSW Government, Plumbing, draining and gasfitting work (licences and registrations). https://www.nsw.gov.au/business-and-economy/licences-and-credentials/building-and-trade-licences-and-registrations/plumbing-draining-and-gasfitting (verified 2026-05-08).
- Queensland Building and Construction Commission, Plumbing and drainage licences. https://www.qbcc.qld.gov.au/licences/apply-licence/available-licences/plumbing-drainage-licences/plumbing-drainage (verified 2026-05-08).
- Consumer, Building and Occupational Services (TAS), Plumbing licences. https://www.cbos.tas.gov.au/topics/licensing-and-registration/licensed-occupations/plumbing (verified 2026-05-08).
- Victorian Building Authority (Building and Plumbing Commission), AS/NZS 3500.4 Heated Water Services: changes to standard. https://www.vba.vic.gov.au/__data/assets/pdf_file/0013/132601/ASNZS-3500.4-Plumbing-and-Drainage-Part-4-Heated-Water-Services.pdf (verified 2026-05-08).
Related
- NCC 2022 Volume Two (residential building code), the companion building code; Volume Three is the plumbing code
- AS/NZS 3000 Wiring Rules, the electrical equivalent of AS/NZS 3500 for plumbing
- Plumber (trade overview), what a licensed plumber covers, licensing, and what to require in their quote
- Plumbing Certificate of Compliance, the document the plumber issues at completion; builder’s gate to occupancy
- Deemed-to-satisfy, how using AS/NZS 3500 satisfies the NCC Performance Requirements without a performance solution
- Backflow prevention, one of the key water services requirements under AS/NZS 3500.1
See also
- Stormwater discharge, where the Part 3 stormwater drain terminates at the boundary
- Tempering valve, the Part 4 device that limits hot water to 50 degrees Celsius at sanitary fixtures
- Sanitary drainage, the below-ground drainage system covered by Part 2
- Notifiable work, which plumbing stages require a mandatory inspection in your state
- NCC (National Construction Code), the regulatory framework that AS/NZS 3500 sits inside
Last updated: 2026-05-08. Verified: 2026-05-08. Quarterly review for currency: check current AS/NZS 3500 edition status at Standards Australia and confirm NCC adoption in each state.