Managing warm water systems with Hydrochem

Recently, there have been wide spread reports of a number of cases of Legionnaires’ disease at the Wesley Hospital in Brisbane. This is an unusual situation because the warm water system has been reported as the source – whereas normally it’s the cooling tower system. How should you minimise the risks associated with warm water systems?

Warm Water Systems

Warm water systems distribute water to showers, hand basins and other outlets throughout facilities such as hospitals, hotels and aged care facilities. A system that stores or supplies water at a temperature between 30°C and 45 – 60°C is considered a warm water system.

The regulations that apply to the control of Legionella in warm water systems vary from State to State. Please contact your local HydroChem consultant to advise you of the specific requirements in your location.

Legionella Risks

Legionella is a common organism in the environment and can be found in very low concentrations in the drinking water supply. Legionella bacteria are able to multiply when exposed to a suitable environment.

Risk Management Plans

HydroChem recommends a risk management approach for the minimisation of risks associated with warm water systems. HydroChem’s approach will be tailored to your installation and the relevant laws in your State.

In assessing the risks associated with Legionella, it is important to:

  • Determine the potential for people to be exposed to respirable sized droplets
  • Identify dead legs including those created by unused outlets
  • Develop a clear plan on what you will do if Legionella is detected

UV Disinfection

Traditionally, it has been common to install UV disinfection units on warm water systems to minimise the growth of Legionella. However, such systems are of limited effectiveness as they rely on transmission of UV light through the water stream – the quartz tubing quickly becomes dirty which blocks transmission of the light.

Consultation with a HydroChem consultant will enable you to best assess the specific requirements of your installation to ensure best practice and legislative compliance.

Water Sampling Strategy

HydroChem recommends that a warm water system Legionella sampling program be implemented at all high risk sites including hospitals and aged care facilities. Sampling frequency should be based on the size and nature of the facility. If Legionella is detected, action must be taken to disinfect the system.

Disinfection Package

In high risk facilities such as hospitals and aged care facilities, HydroChem recommends the installation of equipment to monitor and control disinfection parameters:

  • Compact ORP Controller
  • Industrial ORP probe
  • Diaphragm metering pump (up to 16 bar)
  • Chemical tank with matching bund

HydroChem’s recommended package provides optimum control of disinfection levels, pulse frequency signal for pump control, alarm relay outputs for limit values and mA output signal for reporting to other devices. The system reduces the need for complete circuit flushing.


HydroChem recommends that a maintenance program be implemented to:


  • Maintain and calibrate dosing equipment
  • Replenish disinfection solution stocks
  • Undertake Legionella sampling
  • Report results to all stakeholders


If Legionella is detected, the system must be disinfected. Various methods of disinfection are available. Please speak to your HydroChem consultant to assist in implementing an appropriate method for your warm water system.

Further Considerations

Please speak to your HydroChem consultant about other factors including the maintenance and cleaning of ancillary equipment such as cold water storage tanks, thermostatic mixing valves (TMVs), water hammer arrestors and other water outlets.

Please download the complete information release on the link below.

Legionella – Warm Water Systems

The legislation governing the monitoring of warm water systems, and response to detections, varies from State to State.
To avoid confusion visit our interactive map of Australia designed to clearly explain the legislation (or guidelines) in each state.

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