Thermostatic Mixing Valve Requirements for Bathrooms

What This Requirement Covers

This requirement covers the use of temperature control devices - principally thermostatic mixing valves (TMVs) - to limit the temperature of hot water delivered to sanitary fixtures used for personal hygiene in buildings across Australia. TMVs combine hot and cold water to a preset delivery temperature to reduce scalding risk while still allowing adequately hot supply for hygiene. The rule exists to protect occupants (particularly children, the elderly and people with reduced sensation or mobility) from scalding injuries and to ensure heated water systems meet safe delivery temperatures in new and modified installations.

The requirement applies to new and replacement heated water installations serving personal hygiene fixtures (for example, showers, baths, handbasins) across residential and commercial buildings covered by the National Construction Code (NCC) and the Plumbing Code of Australia (NCC Volume Three). It also interacts with relevant Australian Standards that set performance, commissioning, testing and maintenance expectations for TMVs and heated water systems.

Key Requirements

1. A temperature control device used to deliver heated water in accordance with B2D5
2. (a) must be a thermostatic mixing valve or a thermostatically controlled tap, as specified in NCC Volume Three - Plumbing Code of Australia, Clause B2D6(1).
3. A temperature control device used to deliver heated water in accordance with B2D5
4. (b) may be a thermostatic mixing valve, thermostatically controlled tap, tempering valve, or a temperature-limited water heater (for example limited to 50°C in accordance with AS 3498), as specified in NCC Volume Three - Plumbing Code of Australia, Clause B2D6(2).
5. The required maximum delivery temperature must be achieved in accordance with AS/NZS 3500.4, per NCC Volume Three - Plumbing Code of Australia, Clause B2D6(3).
6. Applications: B2D6 applies to all heated water installations intended for personal hygiene and to new and replacement heated water installations (NCC Volume Three - Plumbing Code of Australia, B2D6, Applications note).
7. TMV work (installation, field testing, maintenance or replacement) must comply with AS 4032.3 - Water supply - Valves for the control of heated water supply temperatures - Part 3: Requirements for field testing, maintenance or replacement of thermostatic mixing valves, tempering valves and end of line temperature control devices (NCC Volume Three - Plumbing Code of Australia, explanatory notes and state variations such as VIC B2D6(4)).
8. Delivery temperature guidance: NCC Volume Three refers to achieving required maximum delivery temperature using the test and commissioning methods in AS/NZS 3500.4 (Water services - Hot water supply systems), which sets methods for verifying outlet temperatures and allowable variances.
9. Temperature limits and choices: Where the NCC permits temperature-limited water heaters, 50°C is a commonly cited maximum in relation to AS 3498 for specific devices; however the NCC requires compliance with AS/NZS 3500.4 for verification of maximum delivery temperatures (NCC Volume Three - B2D6(2) and (3)).
10. Performance and pressure considerations: TMVs must be selected and commissioned for expected supply conditions - typical static/working pressures and pressure differentials should be managed so the TMV can maintain set temperature. AS/NZS 3500.4 and AS 4032 series provide relevant test pressures and procedures.

Relevant references

1. NCC Volume Three - Plumbing Code of Australia, Clause B2D6 Temperature control devices (and B2D5 for delivery temperature requirements).
2. AS/NZS 3500.4 - Water services - Hot water supply systems (for commissioning and temperature verification).
3. AS 4032.3 - Water supply - Valves for the control of heated water supply temperatures - Part 3 (field testing and maintenance of TMVs).
4. AS 3498 (for temperature-limited water heaters) where referenced by NCC Volume Three.

Residential vs Commercial

1. Residential (Class 1 and Class 10A ancillary domestic structures):
2. TMV requirement applies to new and replaced heated water installations intended for personal hygiene in dwellings. The NCC Volume Three B2D6 provision applies irrespective of building class, but designers should give special consideration to vulnerable occupants (infants, older adults) and may specify lower maximum delivery temperatures where appropriate, as encouraged in NCC Volume Three explanatory notes.
3. Commercial (Class 2 to 9):
4. The same core requirement to use a TMV or approved temperature control device for personal hygiene fixtures applies. In many commercial and public settings (childcare, aged care, hospitals, hotels), additional facility-specific guidance, healthcare standards or state regulatory instruments may require more stringent temperature limits, specific TMV performance classes or regular maintenance and testing. For example, healthcare and aged care facilities often require TMVs with higher reliability ratings and documented maintenance regimes, and should comply with AS 4032.3 maintenance/testing requirements.

Key distinction summary

1. The NCC requirement (B2D6) is applicable across building classes for personal hygiene fixtures; differences arise from occupant vulnerability, facility-specific standards and state/territory schedule variations that may tighten or clarify the requirement for particular building uses.

Exceptions and Exemptions

1. B2D6 applies only to new and replacement heated water installations; certain limited replacement scenarios are exempt where specified in application notes - for example, the replacement of a single heated water storage unit within a range or bank of heaters may be treated differently in some state schedules (see NCC Volume Three explanatory notes and state schedules).
2. The NCC allows alternatives to a TMV in some circumstances: for B2D5
3. (b) delivery requirements, a tempering valve or temperature-limited water heater (limited to 50°C per AS 3498) can be used where permitted by B2D6(2). However, the required maximum delivery temperature must still be verifiable in accordance with AS/NZS 3500.4.
4. Some installations can use thermostatically controlled taps in place of TMVs where those taps meet the performance and verification requirements in AS/NZS 3500.4 and relevant parts of AS 4032.
5. Local exemptions: individual state or territory schedules to the NCC may modify or clarify exemptions. Always check the relevant state schedule in NCC Volume Three.

State and Territory Variations

1. The NCC Volume Three includes state variations and inserts for particular jurisdictions. For example:
2. Victoria: VIC B2D6 replaces the national B2D6 wording with substantively similar requirements and explicitly notes that TMV work must comply with AS 4032.3 (NCC Volume Three - VIC B2D6(4)). The Victorian schedule highlights that B2D6 applies to all heated water installations intended for personal hygiene.
3. Other states (NSW, TAS and some jurisdictions) may include specific edits or explanatory wording in their schedules; the NCC Volume Three shows state-specific clauses for B2D6 in several jurisdictions and reiterates that the required maximum delivery temperature must be achieved in accordance with AS/NZS 3500.4.
4. Practitioners must always check the relevant state or territory schedule in NCC Volume Three (Schedules 4-12) for local amendments, as some states may add further requirements for healthcare, aged care or childcare facilities or specify local testing/maintenance regimes.

Practical Compliance Tips

1. Select TMVs rated and certified for the intended application: ensure the valve meets relevant performance expectations and is specified for the expected supply pressures and temperature ranges. Check supplier documentation and compliance with AS 4032 series where applicable.
2. Commission and test outlets in accordance with AS/NZS 3500.4: verify the maximum delivery temperature at the fixture after installation and record commissioning results to demonstrate compliance with NCC Volume Three B2D6(3).
3. Install mixing valves as near as practicable to the outlet group they serve and label them for maintenance access; follow manufacturer instructions and AS 4032.3 for field testing and replacement intervals.
4. Manage pressure and temperature variations: protect TMVs from excessive inlet pressure differences and temperature spikes by fitting pressure-balancing devices or appropriate pressure-limiting valves where required, ensuring the TMV can maintain the set outlet temperature.
5. Provide maintenance and testing records: arrange periodic inspection, field testing and maintenance in accordance with AS 4032.3. For high-risk facilities (aged care, hospitals) adopt documented maintenance schedules and retain records for regulatory inspection.
6. Consider occupant needs when setting outlet temperatures: while the NCC sets verification expectations, lower delivery temperatures should be considered for occupants at greater scald risk; document the rationale and settings used.
7. Check state schedules and facility-specific standards: always verify whether a local schedule or a sector-specific standard (healthcare, childcare, aged care) imposes stricter requirements than the national minimum and incorporate those into specifications and maintenance plans.

References cited inline above are from NCC Volume Three - Plumbing Code of Australia (B2D5 and B2D6), AS/NZS 3500.4, AS 4032.3 and AS 3498 where applicable. Always consult the current published NCC and the relevant Australian Standards and state schedules when designing, installing or maintaining temperature control devices for heated water systems.