The 2025 NCC and AS/NZS 3500 updates have introduced key changes in fire safety, drainage, water systems and EV charging, helping ensure safer, more efficient and compliant buildings. John Chaumont explores what it means for plumbers.

With the imminent, looming release of the National Construction Code (NCC) 2025, it is important to understand which major changes are relevant to the plumbing industry. Several of these can be found within the NCC itself, but of equal importance is the update to the NCC-referenced document schedule, which will call up the 2025 edition of the AS/NZS 3500 suite, rendering the 2021 version superseded.

Although the 2025 editions of both the NCC and AS/NZS 3500 have not yet been formally recognised at a national level, engineers, design practitioners and plumbers in Victoria must commence using them from 20 October 2025.

So, what are the key changes? Because nobody likes homework, the following article has done it for you, providing an outline of the major changes that the plumbing industry should be aware of.

NCC 2025 – Volume 1 2025

Clause E1D3 (e) – Expanded fire hose reel exemption

For fire hose reels, an additional exemption has been allowed for areas less than 100m², so long as they are:

1. Separated from other parts of the building by construction having an FRL of not less than 60/60/60; and
2. Protected with a self-closing fire door having an FRL of not less than –-/60/30; and
3. Provided with fire extinguishers in accordance with AS 2444, located on the egress side of an entry door to the space.

Clause E1D9 – Increased sprinkler requirements for carparks

Fire sprinklers are now required in all class 7a buildings (carparks), including open deck carparks, where:

1. More than 40 vehicles are accommodated; or
2. A car stacker is installed.

Clause F1D4  – Roof and balcony stormwater drainage

A concrete roof, balcony or similar part of a building must have:

1. The structural substrate is graded with a minimum fall of 1:80 to the floor drain, rainwater outlet or other drainage outlet; and
2. A floor drainage system, rainwater outlet or other drainage outlet that is connected to a stormwater drainage system designed and constructed in accordance with AS/NSS 2500.3.

Clause G1D5  – Swimming pool drainage

Pumped discharge from a swimming pool must connect to the sanitary drainage system in accordance with AS/NZS 3500.2.

Clause J1P4 (b) – Provisions for electric vehicle (EV) charging

Okay, so this one is not necessarily plumbing related, but this clause requires mandatory EV charging equipment sufficient to serve:

1. For a class 2 building (residential apartment buildings), charging equipment capable of serving the daily driving needs of all building occupants.
2. For a class 5 to 9 building (commercial buildings), charging equipment capable of serving at least 20% of the daily driving needs of all building occupants (commute to and from work).

NCC 2025 – Volume 2

Clause H2D2 (2) – Pumped discharge from swimming pools

New clause confirming that pumped discharge from a swimming pool may drain a pool by connecting to the sanitary drainage system in accordance with AS/NZS 3500.2.

NCC 2025 – Volume 3 (PCA)

Clause B1V1 – Equation to determine cold water velocity

Velocity performance requirements of 3m/s can now be determined using a new verification method provided in clause B1V1.

Clause B5D7 – Updated examples for cross-connection control scenarios

Specification 41 has been deleted and replaced with Clause B5D7; which has a more clearly structured list of scenarios for determining cross-connection hazard levels for individual, zone and containment protection

Clause B6 & B7 – Updated rainwater storage provisions

Clarification and enhancements were made throughout clause B6 and B7 to rainwater storage requirements, including new provisions covering discharge, tank access, top-up line isolation and contamination control. This brings the NCC in line with AS/NZS 3500.1.

Clause C1V1 & C1V2 – Updated sizing method for sanitary plumbing pipe sizing

New and improved sizing methods have replaced the former method. This came about after receiving feedback from the industry that former methods were not meeting intended levels of performance.

AS/NZS 3500.1 (2025)

Clause 1.3 – Normative references

The list of normative standards in Clause 1.3 has been expanded (normative means must be complied with. These standards are referenced at various places throughout the standard.

• AS 1397, Continuous hot-dip metallic coated steel sheet and strip, coatings of zinc and zinc alloyed with aluminium and magnesium
• AS 1432, Copper tubes for plumbing, gas fitting and drainage applications
• AS 3688, Water supply and gas systems – Metallic fittings and end connectors
• AS 3735, Concrete structures for retaining liquids
• AS/NZS 1546.1, On-site domestic wastewater treatment units, Part 1: Septic tanks
• AS/NZS 4020, Testing of products for use in contact with drinking water
• AS/NZS 4129, Fittings for polyethylene (PE) pipes for pressure applications
• AS/NZS 4766, Rotationally moulded buried, partially buried and non-buried storage tanks for water and chemicals

Clause 2.3.2 – Flexible hose assemblies

Flexible connectors now get their own dedicated clause, the aim being to reduce the risk of failure and subsequent water damage. The clauses align with AS 3499: 2022, Water supply – flexible hose assemblies, where flexible hoses must now meet class-specific pressure ratings outlined in Table 2.3.2.2.

Table 4.4.1 – Atmospheric vacuum breakers listed as a registered testable device

Atmospheric vacuum breakers have been reclassified as a high-hazard ‘registered tested device’, allowing plumbers more options and aligning with global norms.

Clause 4.6 – Atmospheric vacuum breaker amendments

AVBs have now been included with other high-hazard devices, requiring them to meet requirements as line strainers (clause 4.6.1). AVBs have also been relocated from Clause 4.6.3.3 – non-testable devices, to Clause 4.6.3.2 – testable devices.

Clause 5.4.2 – Isolating valves before flexible hoses 

Isolating valves are now required “immediately before each flexible hose assembly connected to a mixer valve, tap outlet or cistern”.

AS/NZS 3500.2 (2025)

Clause 4.9.1.3 (Note) – Stricter requirements for junctions installed on grade

An amendment has been made to a note at the bottom of this clause. If there is ‘sufficient height’ to do so, junctions must be installed with the branch a minimum 15° above the horizontal plane, even if:

1. It is an existing installation
2. Pans are not installed upstream
3. Branches are less than 100Ø

Previously, this was only a recommendation. Now, junctions may only be installed on grade if there is insufficient height.

Clause 13.21 – Connection to tundishes

An additional option for tundish connection has been added, with plumbers now able to connect to disconnector gullies as specified in Clause 4.6.6.

Clause 13.24.2 – Wall-hung urinals

Stricter installation rules (such as increased pipe sizes and grades) have been provided to alleviate identified issues with blockages in wall-hung urinal discharge pipes. The aim is to reduce struvite build‑up, prolong service life and improve overall hygiene.

Section 14 – Sanitary drainage main lines for multi-unit developments

This section has been rewritten to provide greater clarity for the main drainage line design and installation for multi-unit developments. Figure 14.2.1 provides a clear diagram of the requirements.

AS/NZS 3500.3 (2025)

Table 3.3.4 – Design Probabilities

Eaves gutter overflows have been added to this table, requiring an annual exceedance probability (AEP) of 1% in Australia.

Clause 3.5 – Eaves gutter section restructured

The section on eaves gutter design has been completely restructured, providing better readability.

Clause 3.5.3 – New design procedure for eaves gutter overflow

A design procedure for eaves gutter overflow measures has been added for the scenario where all downpipes have been fully blocked and for an AEP as now referenced in Table 3.3.4.

An eaves gutter may also be exempt from overflow measures if eaves gutters are fixed to a veranda or an eave that is greater than 450mm in width and:

1. Has no lining; or
2. Is a raked veranda or a raked eave with a lining sloping away from the building.

Clause 3.6.1 – Maximum valley gutter catchment area

The maximum catchment area for valley gutters has increased from 20m² to 40m² and is referenced in a new graph – Figure 3.6.2, which shows the valley width options for a variety of design rainfall intensities vs. catchment areas. Note that there appears to be an error in this graph, and corrections are underway to have it fixed. Figure 3.6.2 should not be used until further notice is given by Standards Australia.

Clause 3.6.2 – Allowance for computational fluid dynamics (CFD)

An allowance has been made for CFD to be used when designing a valley gutter.

Appendix F – Now mandatory

Appendix F, which was previously informative (recommended, but optional) is now normative, meaning that designers must comply with this section.

Clause F.2 – Formula for calculating overflow volume

A formula has been provided for calculating overflow volume, assuming an AEP of 1%, and all downpipes are blocked.

Clause F.3 – Overflow design

The overflow design shall have a greater capacity than the design overflow volume calculated in clause F.2.

Clause F.4.2 – Provisions for eaves gutter back gap overflow

The method for determining overflow gap behind an eaves gutter has been changed. No longer containing the table of minimum h_f values and figures of acceptable solutions.

Clause F.4.3 – Formula for calculating overflow rate from slotted gutters

A formula has been provided for calculating the overflow rate from the slots in a slotted gutter, expressed in L/s/m, assuming an AEP of 1%, and all downpipes are blocked.

Clause F.4.4 – Provisions for front bead overflow

A specific instruction has been given that if he front bead of the eaves gutter is positioned a minimum of 10 mm below the fascia, the overflow capacity Q shall be taken as 1.5 L/s/m.

AS/NZS 3500.4 (2025)

Clause 2.3.2 – Flexible hose assemblies

Mirroring AS/NZS 3500.1, flexible connectors now get their own dedicated clause.

Clause 10.10.2 – Isolating valves before flexible hoses 

Also mirroring AS/NZS 3500.1, isolating valves are now required “immediately before each flexible hose assembly connected to a mixer valve, tap outlet or cistern”.

General system design

Circulating‑hot‑water sizing and TMV placement clarified improves energy efficiency and Legionella control.

Conclusion

Australian Standards are often updated with key changes being missed by engineers, plumbers and other industry professionals. The ACBC and Standards Australia provide helpful information on which key changes we should keep an eye out for, but as always, it is the responsibility of each professional to perform due diligence and be informed.