Test the waters

18 January 2019

The presence of Legionella in water systems is a serious issue, as it has the potential to cause Legionnaires’ disease. SOCOTEC provides some advice on what steps should be taken all year round to protect against future outbreaks

To flourish, Legionella needs a temperature range from 20-45°C – so warmer weather tends to create an ideal environment for the bacteria to grow and multiply. That is not to say, however, that Legionella is not a risk in the winter months. Although dormant at temperatures below 20°C, Legionella bacteria could still be present, ready to multiply when its optimum conditions are restored. 

Empty facilities and disused water systems often lead to a build-up of stored and stagnant water, which can become a breeding ground for the bacteria. Showers at seasonal facilities, spa pools, and hose pipes for ground maintenance all see a seasonal dip in use throughout winter and, because of this, such facilities require risk assessing and adequate servicing to ensure any risk of Legionella is managed and mitigated.

Ground maintenance in public spaces, parks and grounds also require careful consideration. Like any other water accessory, dispenser or system, hose pipes can store stagnant water – especially with minimised usage in winter due to an increase in rainfall. When those hose pipes and water systems are next used, typically when temperatures have increased, they have the potential to release the airborne bacteria in tiny water droplets for inhalation, posing a risk to the user and anyone nearby. 

Compliance all year round

Even beyond seasonality, the risk of Legionella extends to any hot and cold water systems including cooling towers and heating systems.

Taking steps in keeping your water systems safe should be done in line with a Legionella risk assessment. It’s not just advisory; if you are an employer or in control of premises, you are responsible for understanding the health risks of Legionella. Failure to risk assess water systems for Legionella is punishable by fine and a prison sentence. More often than not, when outbreaks occur, there is a serious risk to human health often resulting in fatalities. 

Under the HSE’s Legionnaires’ disease: The control of legionella bacteria in water systems Approved Code of Practice (ACoP) L8, those responsible for health and safety must adhere to the guidance and recommendations to identify and manage the risk of Legionella in all artificial water systems. 

Here are a number of precautions from SOCOTEC to ensure that you minimise the risk of cases of Legionnaires’ disease and remain compliant:

Controlling temperatures

Keep hot water systems at above 60°C, with water outlets maintained at a minimum of 50°C; in healthcare environments, this should be 55°C. Likewise, cold water should be kept below 20°C, wherever possible. 

Regular system flushing 

Water outlets that are infrequently used should be flushed regularly to avoid stagnation. As a guide, any outlet that has not been used for a week or longer should be flushed for at least three minutes. 

Reduce water stored

Even more effective, reducing the amount of water stored will limit the stagnation of the water and reduce the potential for the growth of Legionella bacteria. If this is not possible, flushing or draining all systems will reduce the risk – and should be outlined as a control measure in the risk assessment. 

Appropriate control measures

Having appropriate control measures such as chemical dosing, water treatment, sampling and regular maintenance can ensure water systems are safe to operate and use. 

Adequate training 

Ensuring staff are appropriately trained in Legionella awareness, risk assessment and their responsibilities can support in effective management and control. Not only that, suitable and sufficient training of all staff involved in risk management is a key requirement of the regulations. 

SOCOTEC can offer support in managing Legionella and conducting your risk assessments: