When Should You Test for Legionella?
In this expert review the water safety specialists at Legionella Control International provide answers to the question … when should you test for legionella?
The review looks at the risks caused by Legionella bacteria in man-made water systems and how those with responsibility can control them to stay the right side of the law. It then goes on to look at why you should consider testing, where and when you should test, and who should do it.
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Preventing the risks from legionella bacteria
Legionella bacteria occur in natural water sources such as ponds, lakes and rivers, yet they can also find their way into man-made water systems like those found in buildings. If allowed to multiply unchecked, legionella can potentially trigger a Legionnaires’ disease outbreak. Since the disease can be fatal, especially among those at particular risk of the illness, the best approach is to prevent its spread to begin with.
If man-made water systems are properly maintained, there should be no reason for the risk level to cause concern. Anyone responsible for maintaining a building should keep this in mind. In the UK, the law states that employers, landlords, and anyone who manages a building or business should make sure they maintain their water system so it does not cause a danger to people.
This typically means keeping the water at a safe temperature that does not sit between 20-45 degrees Celsius (the ideal growth range for legionella). It also means avoiding any scenario where water is allowed to become stagnant or where nutrients are available for the bacteria to feed on and grow.
In practical terms the temperature of the cold water should be kept below 20 degrees Celsius, and the hot water above 50 degrees Celsius (55 in healthcare environments).
Why test for legionella bacteria?
Legionella testing is one way of assessing the condition of the water and the system, monitoring the level of Legionella bacteria within. According to the Health and Safety Executives HSG274 Part 2, the technical guidance for the control of legionella and Legionnaires’ disease, the water in domestic hot and cold water systems does not usually need to be sampled and tested. However, since all scenarios, buildings, and water systems are different, the risk management process should always begin with a legionella risk assessment. This should identify where the risks are and whether they can be safely removed or whether steps should be taken to reduce the risk to a safe level.
A risk assessment should always be your starting point in the legionella control process …
Legionella testing can provide a method for assessing the safety of the water supply and system used. For example, let’s assume you complete your risk assessment and determine that regular chemical dosing of the system is ideal for keeping bacteria under control. At this point, you may wish to test the water weekly to make sure the dosing is correct and is achieving the desired effect. Alternatively, you may find that a particular area of the water system may be at greater risk of an increase in bacteria. In this instance, legionella testing would also be prudent to help determine whether there is an increased risk, and if so, what measures can be taken to reduce that risk to keep people safe.
In some cases, though, testing for legionella is required to be carried out. The best example of this is with a cooling tower. Wet cooling towers present a specific risk, whereby bacteria could become airborne in water droplets spread over a potentially wide area. In this case, quarterly testing is required as a minimum unless the results of the legionella assessment indicate that it should be done more often, if positive samples have already been found, if an outbreak of Legionnaires’ disease has been identified locally or when commissioning the towers or establishing a new treatment programme.
When should you test for legionella?
When you conduct a legionella risk assessment, you are looking for signs that suggest one or more parts of the water system would present the ideal environment for Legionella bacteria to multiply and spread.
For instance, you may inspect the water system and notice there are areas that are rarely used, such as a shower room in a quiet part of a residential care home or hospital. There may be stretches of pipework that are no longer in use, known as dead legs or dead ends. Rarely used water outlets should be removed where possible or if they can’t, they should be regularly flushed through to keep the water moving and get rid of the risk of stagnant water. This could increase the risk of sediment and scale, which in turn would feed the bacteria. If a risk assessment identifies any dead legs, they should also be removed to eliminate the risk.
Where to test for legionella?
No two water systems are identical, but we have seen how the risk assessment should identify any potential areas of concern. If you identify water outlets that are infrequently used, these would be ideal to test. You may also find areas where the water temperature is close to the range that would allow the bacteria to multiply (between 20-45 degrees Celsius). Indeed, the temperature of the water is often a key factor that can help pinpoint potential risk areas.
If you have storage tanks to store hot or cold water, it is a sensible idea to check the temperatures are within a safe range. Thermostatic mixer valves (TMVs) should always be fitted to taps whenever there are users who are likely to present a scald risk. These should help ensure the water temperature is at a safe level, both for users and to ensure it does not drop to an unsafe level for the
Who should test for legionella?
The responsibility for legionella testing will always be with those who are responsible for maintaining the hot or cold water systems for the building. However, it is possible to hire an expert to conduct the water testing for you, along with the legionella risk assessment if you do not feel you can do so safely. The more complex the water system is, the more likely it is that you would benefit from hiring an expert in assessing legionella risk and dealing with that risk. It could be the best way to protect your business and everyone who uses it.
Leading legionella and water safety specialists
Legionella Control International are experienced legionella and water safety specialists supporting those responsible for the control of waterborne pathogens including legionella in the workplace. We help businesses protect their workers, customers and others from the dangers caused by water systems, helping them to meet their health and safety compliance obligations in this specialist area.
We are experienced in all aspects of legionella and water safety and deliver a full range of services including legionella sampling and water safety risk assessments. We also offer compliance auditing, water quality testing, City & Guilds training and other health and safety risk management services that help keep staff and others safe.
If you would like to speak with one of our legionella specialists about improving your risk management processes call us today on 0330 223 36 86 or contact us here …
