AS 3500 Explained: Australia's Plumbing and Drainage Standard
What is AS 3500?
AS/NZS 3500 is Australia's plumbing and drainage standard. It governs how cold water is delivered to a building, how waste and soil leave it, how stormwater drains from the roof and surface, and how hot water is generated and circulated. It is the document a hydraulic engineer designs to and a licensed plumber installs from.
The standard is published as a multi-part series. Each part covers a discrete area of plumbing work: water services, sanitary drainage, stormwater drainage, heated water services, and Class 1 domestic installations. There is also a glossary part. Most commercial projects need Parts 1, 2, 3, and 4 in parallel.
The Plumbing Code of Australia, published as Volume Three of the National Construction Code, calls AS 3500 up as the deemed-to-satisfy compliance pathway. State plumbing legislation requires that all plumbing work covered by AS 3500 be carried out by a licensed plumber. Engineers can specify and certify the design, but installation is a licensed trade.
Where AS 3500 Fits in the Plumbing Standards Stack
AS 3500 sits alongside several adjacent documents that engineers, plumbers, and certifiers hit on a typical project. Use this map to find the correct part.
| Standard | What it covers | When you need it |
|---|---|---|
| AS/NZS 3500.0 | Glossary of terms | Reference for terminology, no design content |
| AS/NZS 3500.1 | Water services (cold water) | Most commercial buildings |
| AS/NZS 3500.2 | Sanitary plumbing and drainage | Most commercial buildings |
| AS/NZS 3500.3 | Stormwater drainage | Roof drainage, surface drainage, OSD |
| AS/NZS 3500.4 | Heated water services | Hot water systems, scald protection |
| AS/NZS 3500.5 | Domestic installations | Class 1 houses only |
| AS/NZS 3666 | Microbial control of water systems | Cooling towers, warm water systems |
| Plumbing Code of Australia | Performance and DTS framework | Calls up AS 3500 nationally |
AS 3500 is the toolkit. The Plumbing Code of Australia (NCC Volume Three) decides which parts apply to your building.
What AS 3500 Covers
Water Service Sizing (AS 3500.1)
Cold water supply from the property boundary to every fixture. Pipe sizing is set by fixture units, design flow rate, and acceptable pressure loss across the system. The standard also covers isolation valves, water meters, and backflow protection devices, which must be sized and located to match the hazard rating of the connection. See our hot and cold water system design and backflow prevention requirements memos for more detail.
Sanitary Plumbing and Drainage (AS 3500.2)
Waste and soil pipework from every fixture out to the sewer connection. Fixture unit calculations set pipe size; vent sizing and trap requirements protect against siphonage and odour; minimum slopes guarantee self-cleansing flow. Get any of these wrong and the system blocks, smells, or rejects in commissioning. Our sanitary plumbing and drainage design and sanitary fixture counts memos cover the design rules and the fixture count tables.
Stormwater Drainage (AS 3500.3)
Roof drainage, gutter and downpipe sizing per AEP rainfall events, surface drainage, and on-site detention (OSD) where the local council requires it. The 2021 edition uses AEP terminology aligned with current Australian Rainfall and Runoff guidance. See our stormwater drainage for commercial buildings memo for the design workflow and council overlay considerations.
Heated Water Services (AS 3500.4)
Hot water generation, storage, ring main design, dead leg limits, and thermostatic mixing valves (TMVs) for scald protection. Healthcare, aged care, early childhood, and disability access settings have specific TMV requirements that cap delivered water temperature. Class 9 buildings have additional clauses around TMV servicing and labelling.
Trade Waste and Pre-Treatment
Grease traps for food premises, oil/water separators for car parks, and dental amalgam separators for dental clinics. Each council and water authority (Sydney Water, Hunter Water, and equivalents in other states) has its own trade waste agreement requirements that overlay AS 3500. A fitout brief that ignores the trade waste application path stalls at handover.
Which Edition Applies to Your Project?
The 2021 editions of Parts 1 to 4 are current for new commercial projects. Part 5 (Class 1 housing) is still at its 2018 edition. Older projects and retrofits may need to be read against the prior edition that was current at approval.
| Edition | Status | When you'd use it |
|---|---|---|
| AS/NZS 3500.1-5 (2018) | Older edition | Pre-2021 projects, retrofit reference |
| AS/NZS 3500.1-4 (2021) | Current | All current commercial projects |
| AS/NZS 3500.5 (2018) | Current (no 2021 update) | Class 1 housing |
Confirm the edition with your certifier and the local plumbing authority. Sydney Water and other water authorities sometimes have their own supplementary requirements.
Most-Asked Questions
- What is AS 3500? Australia's plumbing and drainage standard, called up by the Plumbing Code of Australia (NCC Volume Three) as the deemed-to-satisfy pathway.
- What is the difference between AS 3500.1, .2, .3, .4 and .5? .1 is water supply, .2 is sanitary drainage, .3 is stormwater, .4 is hot water, .5 is Class 1 housing.
- Is AS 3500 mandatory in Australia? Yes for plumbing work covered by the PCA. The alternative is a Performance Solution.
- Do I need a licensed plumber to do AS 3500 work? Yes. State plumbing legislation requires licensed plumbers for all sanitary and water service work.
- What is the difference between the PCA and AS 3500? The PCA is the regulation (NCC Volume Three). AS 3500 is the technical standard the PCA calls up.
- What edition of AS 3500 applies to my building? Most current commercial projects use the 2021 editions of Parts 1 to 4. Part 5 (housing) remains at 2018. Confirm with your certifier.
- Does AS 3500 cover hot water scald protection? Yes. AS/NZS 3500.4 sets TMV (thermostatic mixing valve) requirements for healthcare, aged care, and disability access settings.
Three Compliance Traps We See Most
- Wrong edition cited. Documentation drafted to the 2018 edition lodged with a certifier requiring 2021. Confirm at kickoff and lock the edition into the specification cover sheet.
- Stormwater drainage sized to ARI instead of AEP terminology. AS/NZS 3500.3:2021 uses AEP (Annual Exceedance Probability), aligning with current Australian Rainfall and Runoff guidance. Older projects cited ARI (Average Recurrence Interval). The values are not directly equivalent and the documentation must use the correct framing.
- Trade waste assumed to be just AS 3500. Each water authority (Sydney Water, Hunter Water, and equivalents) has its own trade waste agreement requirements that sit on top. Most fitouts with food, vehicle, or industrial waste need a separate trade waste application. See our trade waste requirements memo for the NSW workflow.
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References
- AS/NZS 3500.1:2021, Plumbing and drainage, Part 1: Water services, Standards Australia.
- AS/NZS 3500.2:2021, Plumbing and drainage, Part 2: Sanitary plumbing and drainage, Standards Australia.
- AS/NZS 3500.3:2021, Plumbing and drainage, Part 3: Stormwater drainage, Standards Australia.
- AS/NZS 3500.4:2021, Plumbing and drainage, Part 4: Heated water services, Standards Australia.
- AS/NZS 3500.5:2018, Plumbing and drainage, Part 5: Domestic installations, Standards Australia.
- National Construction Code 2025, Volume Three Plumbing Code of Australia, ABCB.
- AS/NZS 3666, Air-handling and water systems of buildings, Microbial control series, Standards Australia.