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Updated plumbing and drainage standards - Part 4: Heated water services

AS/NZS 3500.4:2025

On 17 April 2025, Standards Australia published AS/NZS 3500:2025 plumbing and drainage to replace the 2021 edition. It is a referenced standard in the Plumbing Code of Australia, which is adopted under the Plumbing Regulations 2018.

Plumbing practitioners must ensure all plumbing work commenced on or after 20 October 2025 complies with the 2025 version of the standard. 

Overview of the key changes in the updated standard

Broadly, the key changes in the 2025 edition of AS/NZS 3500.4 are:

  • New requirements specifying the use of certain classes of flexible hose assemblies in heated water applications (clause 2.3).
  • New requirement for an isolating valve to be installed immediately before each flexible hose assembly is connected to a mixer valve or tap outlet (clause 10.10.2).
  • Editorial changes that make the standard easier to read.

Summary of key changes since the 2021 edition

2.3 Pipes, fittings and connectors – General limitations

Clause 2.3.1
Pipes and fittings

(Update to clause)

This change accommodates the different pipe description methods – some 100 mm pipes are referred to by internal, nominal, or external diameter. As a result, 110 mm has now been included instead of 100 mm.

2.3.2 Flexible hose assemblies

Clause 2.3.2.1
Accessibility

(New clause)

The requirements regarding flexible hoses have been relocated to this clause (previously in Clause 2.3(c) of the 2021 edition). The requirements have not changed.

Clause 2.3.2.2
Classification

(New clause and new table)

Flexible hose assemblies are categorised into four different classes based on their application, as follows:

Class 1 are end of line flexible hoses with an open end (i.e. no isolation device after the inlet of the hose). Class 1 must only be used for dynamic pressure applications (i.e. must not be used for static pressure applications).

Classes 2 or 3 are flexible hoses used to connect between fixed points. Classes 2 or 3 are used for static pressure applications.

(Note: fixed points are between rigid supply lines and a fixture, fitting, valve, tap, appliance or similar, or fixed points are between supply line to supply line to allow for expansion or movement.)

Class 4 are end of line flexible hoses with an integral stop valve or trigger. Class 4 are used for static pressure applications.

Flexible hose assemblies must meet the requirements in Table 2.3.2.2. Plumbing practitioners need to know the maximum operating pressure and maximum hose length that relates to each class of flexible hose.

Table 2.3.2.2 Flexible hose assembly classification

Class For the following application Class of hose – description Class of hose – limitations

Class 1

Hoses that have no isolation device after the inlet of the hose.


Class 1 hoses must not be used under static pressure.

End of line hoses with an open end.
  • Max operating pressure: < 250 kPa
    (for use under dynamic pressure).

  • Max length: 10 m
Class 2 Connections between fixed points. Flexible connectors ≤ 20 mm
  • Max operating pressure: 1,400 kPa  
    (for use under static pressure).
  • Max length: 2 m
Class 3 Connections between fixed points. Flexible connectors > 20 mm and ≤ 32 mm.
  • Max operating pressure: 25 mm = 1,400 kPa 32 mm = 1,350 kPa (for use under static pressure).
  • Max length: 10 m
Class 4 Hoses for wash down tapware or hoses that have an isolation device after the inlet of the hose. End of line hoses with shut-off devices, pressurised.
  • Max operating pressure: 1,400 kPa  
    (for use under static pressure).
  • Max length: 10 m for < 25 mm 2 m for ≥ 25 mm

Clause 2.3.2.3
Operating temperature

(New clauses)

Plumbing practitioners must use the flexible hose suited to the application. The marking on the flexible hose specifies the suitable application.

Clause 2.3.2.4 Submerged applications

ApplicationMarking
Up to 70° C

Rated to this temperature and hoses marked with “70° C” or “L”

or

Hoses marked with “90° C” or “H”

Up to 90° C Rated to this temperature and hoses marked with “90° C” or “H”
Submerged applications Rated for submersion and hoses marked with “S”

2.3.3 Semi-flexible hose assemblies

Clause 2.3.3
Semi-flexible
hose assemblies

(New clause)

  • Semi-flexible hoses must:
    • only be used in accessible locations
    • not be buried
    • not be used where repeated movement is expected.
  • Explanatory note: semi-flexible hoses are commonly called ‘semi-rigid hoses.’
  • Examples of installations of semi-flexible hoses include connections of appliances, tapware, water heaters, expansion joints, seismic joints, or offset connectors.

5.4 Protection against damage from leaking water

Clause 5.4.2
Unconcealed
water storage tanks

(Update to clause)

No change in requirements. The clause has been re-worded to clarify the following:

  • All unconcealed water storage tanks that are installed inside buildings must be installed with safe trays (as specified in Clause 5.4.3) and safe wastes (as specified in Clause 5.4.4) – except for:
    • Unconcealed water storage tanks installed inside buildings on or above a floor surface that is impervious to water and suitably drained to a trapped or untrapped floor drain or an external doorway (which do not require safe trays).
    • A mains pressure water heater with a leak protection device fitted adjacent to the cold-water inlet and upstream of any expansion control valve which does not require a safe waste.
  • Safe trays are not required for:
    • Free outlet-type storage water heaters up to 13.5 L capacity
    • Instantaneous water heaters.

10.10 Isolating valves

Clause 10.10.2
Location

(Update to clause)

  • Isolating valves must be installed immediately before each flexible hose assembly connected to a mixer valve or tap outlet.

Updated plumbing and drainage standards AS/NZS 3500 series

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Last updated 30 June 2026
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