Frequently Asked Questions

Q. What laboratory do I send my water sample to for Legionella testing?
A. You can search National Association of Testing Authorities Australia (NATA) for laboratories possessing accreditation for Legionella analysis at

Q. Can I use other water test kits to see if Legionella is in the water?
A. Yes, you can use other water test kits or methods for monitoring the presence of Legionella such as colour indicator tests. Tests such as these are not considered to be prescribed tests and don’t require notification to the department. They may be useful in indicating the effectiveness of your water system management operations without the costs associated with prescribed tests.
Prescribed tests will still need to be carried out on water samples as part of the water risk management plan requirements.

Q. Does a negative test for Legionella mean my water system is clear of Legionella?
A. No. Once a water system has been colonised by Legionella it is very difficult to eradicate it. Legionella colonisation varies over time. A negative test indicates that Legionella was not detected in the water on that occasion. Legionella has the capability to be present in a water distribution system without being detected. This can occur when:
• Legionella is present in the biofilm with other bacteria. The biofilm offers protection from external stressors, such as disinfectants and temperature increases and enables the Legionella to continue to multiply
• It is in a stable form (dormant and viable) that is unable to be cultured. When conditions are right the Legionella will cease to be dormant and commence multiplication
• They are inside protozoan host. They can multiply rapidly inside the host and when the host dies large numbers of Legionella will be released into the water system
A negative test for Legionella is not a substitute for primary prevention through proper operation of controls. The key focus should be on operational control of the water system via maintenance practices, disinfection, temperature control, routine preventative actions (e.g. flushing in low use areas) and good system design.

Q. What do I do if Legionella is consistently being detected at an outlet?
A. This depends on where Legionella has been detected and the purpose for the sample site selection. You should consider how many other samples from a sampling event were also positive for Legionella. Also, were the positive detections associated with a part of the site sample or were they widespread?
Initially try and work out where the source of the contamination is coming from. Consider the actions undertaken to date. Have they been successful at any stage?  A first flush water sample detection where the flushed samples are negative for Legionella indicates that the contamination could be linked to the outlet. When was the last time the outlet was cleaned or replaced? If not recently, have the outlet cleaned or replaced in the first instance. The outlet should be removed (if possible), physical and chemically cleaned (to remove line scale and rust deposits) and then disinfected before reinstallation.
Consider the outlet use frequency. If it is intermittent then it is possible that the water is remaining in the outlet too long. Consider routine flushing of outlets to avoid stagnation (if chlorine residual is sufficient) and follow up to make sure the flushing is undertaken.
If it is the cold flush samples that are consistently positive for Legionella at this outlet then there could be contamination of the line. Is the outlet connected to a TMV? Are any other outlets connected to the TMV are their results the same? If so, when was the TMV last serviced and replaced. TMVs should be cleaned annually and replaced every five years. Check the records to see when this was done. This should be part of your operational activities to manage risk. If it hasn’t been done the TMV could be the source of the contamination. Consider arranging TMV servicing and cleaning. Additionally, the water line from the TMV to the outlet may also be contaminated. This can be addressed in many ways such as flushing (dependent on colony units detected, chlorine residual, water pressure), pasteurisation, disinfection (super chlorination) and use of biocides.
If it is the hot flushed sample, check the temperature of the hot water system. Was it above 600C? if not then the temperature should be adjusted. Was the temperature consistent throughout the system or was there a decrease in temperature? If so, check to see whether there was cross over. Were the pipes insulated and in good repair?
Check for deadlegs as these can continually be a source of contamination despite the actions being undertaken. Any deadlegs found should be removed.

Q. I am not sure if I am taking too many water samples for Legionella testing, why isn’t there a standard number of samples required to be taken based on facility size?
A. Verification monitoring i.e. water tests for Legionella, is for checking to see whether the operation and maintenance actions that were identified by the water hazards risk assessment are effective. Each facility will have a different risk profile based on factors such as those listed below.
Factors that can influence the number of samples taken can include:
• services provided by the facility
• devices used by the facility
• health and age of the inpatients
• opportunity for inpatients to be exposed to the water
• outcome of the risk assessment
• level of risk accepted by the facility management
• age of facility, quality and age of water infrastructure i.e. fixtures and fittings
• onsite water treatment processes
• quality of incoming water supply
Factors such as those listed above, all inform the decision-making process for establishing the sampling program. The number of samples and the sampling locations should be sufficient to indicate whether there are issues with the water system or not.

Q. Why isn’t there a standard set of remedial actions based on colony size when Legionella is detected?
A. Responding to Legionella detections is dependent on individual circumstances. Risks can vary significantly depending on factors such as:
• Services the facility provides
• The health status of the patients or residents at the facility
• The quality of the incoming water supply
• Design limitations of the facility
• Where the detection was located and opportunity for exposure of vulnerable persons
• Level of acceptable risk determined by the facility – this may vary depending on the vulnerability of the persons exposed to the risk. For example, a facility may have a goal that no Legionella should be detected in the transplant ward whereas in other areas of the facility that same level of action is not required e.g. consulting rooms or doctors living quarters
It is best practice to appraise all the information gathered through the water system monitoring actions. Testing the water for the presence of Legionella is to determine whether your operating actions are sufficient to manage the growth of Legionella not to see if it is there and only then to manage it.

Q. Flushing an outlet is inconvenient and wastes water, why is it important that it be done?
A. Biofilm can grow in areas where there is low water flow. Flushing the water system reduces the opportunity for water to stagnate. Additionally, Legionella is sensitive to chlorine and flushing can be an effective management action provided the chlorine residual is sufficient. It is important that flushing is carried out with minimal creation of aerosols particularly if vulnerable people are present.

Q. Are TMVs required on all taps?
A. No. TMVs should only be used for outlets where the there is a risk of scalding harm to inpatients.  (Check with your local Health department about State regulations. ) 

Q. I am in Queensland, is a water risk management plan required for a prescribed facility if it is not receiving inpatients yet?
A. It is best practice to have a water risk management plan that covers the commissioning phase of a facility. The commissioning phase of a building is very important as this is when the water distribution system has been connected but water can stagnate in the pipes if it is not regularly drawn through the system. Allowing stagnation in new pipes may result in the development of biofilm in the water system.

Q. What does it mean if the chlorine residual drops at points throughout the water distribution system?
A. This indicates that there is something utilising the free chlorine between those points. This could be the result of a temperature increase or presence of biofilm such as a dead leg. Check the system to determine what the factor may be and adjust the actions to address it and continue to monitor it to ensure that chlorine residual is maintained throughout the system.

Q. What should be considered if my facility is thinking of installing a chlorine dosing plant to address Legionella detections?
A. Installing chlorine dosing facilities can be expensive and require a certain level of expertise to manage them. It is important to appreciate that a chlorine dosing plant may not necessarily provide the outcomes sought. Chlorine dosing plants introduce other hazards to the water system which will then need to be managed.
Some common things to consider should include:
• Chlorine dosing requires online monitoring to ensure correct dosing and interlocks to prevent overdosing. This all adds to the complexity and cost of chlorine dosing
• What healthcare services are reliant on water of a specific quality. Renal care equipment is particularly sensitive to chlorine and chloramines so need to ensure any changes to the water quality are compatible
• Water usage patterns
• Consistency of water pressure
• Systems can cause pipe erosion which can then contribute to biofilm development
• Whether water supply is chlorinated or chloraminated. Installing a chlorine dosing plant on a chloraminated supply is problematic as break point needs to be achieved to prevent free chlorine levels from declining. The only chloraminated drinking water supplies in Queensland are those supplied from the Seqwater Mt Crosby and North Pine water treatment plants. If you are in SEQ, to find out if your drinking water retailer supplies chloraminated water you should contact them directly. If your facility does receive chloraminated water and you are considering installing your own disinfectant dosing you are advised to seek information first from an independent water specialist, who may be able to advise on the best treatment option for your situation.
Additional information can be found at

Q. I’m getting detections in my flushed hot water samples.  What should I do?
A. Chlorinating the hot water distribution system is difficult to manage.  Temperature affects the free chlorine and the chlorine residual will be difficult to manage.
• Check the temperature of the hot water throughout the system. Legionella is sensitive to temperatures above 600C and so the system temperature may need to be increased to ensure ongoing control of Legionella
• Inspect the pipe insulation as this may need to be replaced or installed if it is absent from hot water pipes– this will reduce heat transfer from the hot to the cold-water pipes and help maintain the circulation temperature of water

Q. Why is Legionella such a big issue when patients can get other infections like the flu from attending a health care facility?
A. Health care facilities have an obligation to provide a safe environment for patients, staff and visitors. Legionellosis is a health care associated infection from an environmental source (water) used by the facility. It is a preventable adverse event related to the operation of the facility rather than person to person transmission such as with the flu. It is possible to significantly reduce the rate of Legionella infections through prevention and control.
It is an expectation of the public that when they attend a healthcare facility that the environmental conditions of the facility are safe. Legionella is a known hazard to water systems and the facility should take appropriate control actions to minimise the risk to the water system.

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