Hot Water System Installation Requirements and Safety

What This Requirement Covers

This requirement covers the safe installation, commissioning and temperature control of heated water systems used for personal hygiene and other building services across Australia. It exists to prevent scalding injuries, ensure sanitary delivery of hot water, protect storage vessels from overpressure or excessive temperature, and control risks such as Legionella amplification in stored hot water. The rules apply to new installations and many replacement or altered heated water services so that occupants are protected regardless of the type or location of the heater.

These provisions primarily sit in the Plumbing Code of Australia (PCA) contained in NCC 2022 Volume Three and apply to heated water installations connected to sanitary fixtures. They are relevant to designers, plumbers, certifiers, builders and building owners across all building classes where heated water is provided for personal hygiene or similar uses.

Key Requirements

1. Maximum delivery temperature: Heated water supplied for personal hygiene must be limited to the maximum delivery temperatures specified and achieved in accordance with AS/NZS 3500.4 (as specified in NCC 2022 Volume Three, B2D6(3)).
2. Accepted temperature control devices (NCC 2022 Volume Three, B2D6):
3. For the delivery requirements in B2D5
4. (a) (immediate-use situations), the temperature control device must be a thermostatic mixing valve or a thermostatically controlled tap.
5. For the delivery requirements in B2D5
6. (b) (where a maximum delivery temperature is mandated), the device must be one of: thermostatic mixing valve, thermostatically controlled tap, tempering valve, or temperature-limited water heater (see relevant state text where it specifies marking and limits).
7. 50°C reference: Several state schedules and explanatory notes reference a 50°C maximum delivery temperature for some temperature-limited water heaters or tempering arrangements (see state-specific clauses and AS 3498 marking requirements) - compliance must be demonstrated against AS/NZS 3500.4 and any state schedule requirements (NCC 2022 Volume Three, B2D6 and state variations).
8. Heated water storage safety (NCC 2022 Volume Three, B2D7):
9. Storage containers used for producing or storing heated water must be fitted with a temperature and pressure relief device in accordance with AS/NZS 3500.4.
10. Temperature control device testing and maintenance: Thermostatic mixing valves and tempering devices must meet field testing, maintenance and replacement requirements in AS 4032.3 (see state-specific inserts such as VIC B2D6 and explanatory notes).
11. Legionella control (NCC 2022 Volume Three, B2D8): Facilities for storing and distributing heated water should meet the PCA provisions for Legionella risk control; designers must consider storage temperatures, dead legs and maintenance to minimise growth (see PCA B2D8 and AS/NZS 3500 series guidance).
12. Applications and scope (NCC 2022 Volume Three, B2D6 Applications):
13. B2D6 applies to all heated water installations intended for personal hygiene. It applies to new heated water services and, depending on state text, to replacement or relocated heaters and to alterations or extensions of existing heated water services.
14. Exemptions noted in the PCA: Some replacement actions (for example, replacement of a single heating unit within a range or bank of heaters) may be exempt from installing a temperature control device under certain circumstances (see state notes and B2D6 Exemptions).

Residential vs Commercial

1. Residential (Class 1 and Class 10 ancillary structures):
2. The PCA requirements for temperature-limited delivery for personal hygiene apply to Class 1 dwellings. Where occupants are young children or older adults, designers and owners should adopt lower delivery temperatures than the maximum in B2D5
3. (b) as a risk mitigation measure (NCC 2022 Volume Three explanatory information).
4. Temperature control devices permitted include thermostatic mixing valves or thermostatically controlled taps for immediate-use systems. Where storage is used, tempering devices or temperature-limited water heaters may be acceptable subject to NCC and AS/NZS 3500.4 compliance.
5. Commercial and multi-residential buildings (Class 2 to Class 9):
6. The same PCA provisions apply for personal hygiene outlets, but system complexity, distribution runs, and occupant mix increase the emphasis on correct selection, installation, commissioning and maintenance of thermostatic mixing valves, tempering valves, and relief devices. Larger storage tanks require appropriate temperature and pressure relief devices and Legionella risk controls (NCC 2022 Volume Three, B2D7 and B2D8).
7. In multi-occupancy buildings (Class 2 and some Class 3/5/9), designers must also consider shared systems, central plant, and service access for periodic field testing and maintenance in accordance with AS 4032.3 and AS/NZS 3500.4.

Exceptions and Exemptions

1. Exemptions in the PCA: B2D6 includes limited exemptions where the clause does not apply to replacement of a single heated water storage unit within a bank or manifold of heaters (NCC 2022 Volume Three, B2D6 Exemptions). Check the exact state or territory insertion for how this exemption is framed.
2. Scope-limited application: Some PCA clauses apply only to new heated water services or to replacements and alterations (state texts modify this in some jurisdictions). Review the specific application statements in Volume Three to confirm whether a proposed work falls within the clause.
3. Alternative solutions: Alternative compliance solutions are possible where an alternative can demonstrate equivalent safety to the deemed-to-satisfy (DTS) provisions. Any alternative must be supported by evidence, test data and accepted by the relevant certifier or authority having jurisdiction.

State and Territory Variations

1. The Plumbing Code of Australia (NCC Volume Three) contains state and territory schedule inserts that modify or replace national text. Notable variations include:
2. New South Wales: NSW text clarifies that B2D6 applies to all new heated water services and to replacing a hot water heater regardless of type or location; it also reiterates the 50°C marking requirement for temperature-limited water heaters (NCC 2022 Volume Three, NSW B2D6).
3. Victoria: VIC B2D6 replaces B2D6 with wording that repeats the device options and requires achievement of the maximum delivery temperature in accordance with AS/NZS 3500.4; VIC also references AS 4032.3 for field testing and maintenance requirements for thermostatic mixing valves.
4. Tasmania and other jurisdictions: Some states insert their own B2D2/B2D6 variations or explanatory notes - always check the relevant state schedule in NCC 2022 Volume Three (Schedules 4-12) for local amendments that may affect device types, temperature limits or application scope.
5. Reminder: Always verify against the state schedule in NCC 2022 Volume Three for your jurisdiction because schedules may add or modify requirements for temperature control devices, marking and exemptions.

Practical Compliance Tips

1. Install the right device: Use a thermostatic mixing valve or thermostatically controlled tap where required by B2D6; avoid using basic check valves or non-thermostatic mixing arrangements for personal hygiene outlets.
2. Commission to AS/NZS 3500.4: Verify and record final outlet temperatures and settings in accordance with AS/NZS 3500.4; incorrect commissioning is a common non-compliance.
3. Fit relief devices on storage: Always fit a temperature and pressure relief device to storage vessels as required by B2D7; ensure the relief discharge is routed safely and inspected for corrosion or blockage regularly.
4. Mark and document temperature-limited heaters: Where temperature-limited water heaters are used, ensure marking and documentation meet the referenced standard (for example, AS 3498 marking where relevant in state text) and that the device is limited to the permitted maximum (often 50°C where specified).
5. Plan for maintenance and testing: Specify access for periodic field testing, maintenance and replacement of thermostatic mixing valves in accordance with AS 4032.3; include maintenance responsibilities in O&M manuals.
6. Consider occupant vulnerability: For dwellings with young children, older persons or healthcare occupants, set lower delivery temperatures than the maximum permitted and consider secondary protection such as point-of-use thermostatic mixers.
7. Check state schedules early: During design, review the relevant state schedule in NCC 2022 Volume Three (Schedules 4-12) to capture local variations, exemptions or additional marking/testing requirements that could affect product selection and documentation.

Citations: PCA (NCC 2022 Volume Three - Plumbing Code of Australia), clauses B2D5, B2D6, B2D7, B2D8; AS/NZS 3500.4; AS 4032.3; AS 3498 where referenced by state text. Note: verify the applicable state schedule in NCC 2022 Volume Three (Schedules 4-12) for jurisdiction-specific modifications.