In NSW, warm water systems (including those using thermostatic mixing valves – TMVs) are considered a regulated water system because they can create conditions where Legionella bacteria may grow and be transmitted to people. These systems are regulated under the Public Health Act 2010 and the Public Health Regulation 2022, and there arespecific obligations for owners and occupiers to manage them safely.
A warm water system typically supplies water at temperatures between roughly 30–60 °C, which unfortunately is within the range where Legionella thrives and can multiply.
Thermal Flushing in Warm Water Systems is used to target and reduce Legionella risk for the following reasons:
Legionella pneumophila grows most readily in water between ~25–45 °C — exactly in the warm water range.
Thermal flushing uses elevated temperatures (above normal operating temps) to:
Heat water to >60 °C at outlets so bacteria are killed or reduced
Flush dead or stagnant water from the system
Disrupt bacterial biofilm in pipes and TMVs that can harbour Legionella
This is a recognised control action in Legionella risk management plans (often required under Australian and NSW guidance) even though NSW Health’s publicly-available documents focus on system approval and mandatory monitoring rather than prescribing exact flushing procedure steps.
NSW Policy Directive PD2015_008 — “Water – Requirements for the provision of cold and heated water”
Applies mainly to hospitals but sets out the basis for operational monitoring of warm water systems to manage Legionella risks.
It includes the requirement for at least a monthly temperature safety check from an outlet to verify system performance (e.g., correct hot/cold delivery).
NSW Health Warm Water System Documents
NSW Health provides inspection forms and guidance on operation & maintenance of warm water systems (which form part of risk controls and Legionella management).
Although these documents do not fully publish detailed thermal flush protocols, they support:
Evidence of a risk management plan
Routine checks and maintenance
Keeping records of checks and corrective actions
And under the Regulation, warm water systems must be installed and maintained so as to minimise the risk of Legionella growth and transmission.
Bertram & Sons brings expert insight into warm water management and testing. Our team works with high-risk environments, ensuring that every sample and result is handled with precision and urgency. We’re committed to delivering high standards of safety and accuracy.
Reach out today to discuss your microbiological sampling needs. We’re here to help you develop a safe, compliant water management strategy backed by accurate testing and expert support.
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