The Risk of Legionella in Water Systems

When buildings reopen after lockdown, it is essential that water systems are not put back into use without considering the risks of Legionnaires' disease.

If you are a business owner or operator, or you manage a water system, you need to be aware of the risks of legionella around water stagnating.

There is an increased risk of waterborne pathogens such as Legionella bacteria being present because of the conditions that lockdown may have created.

Legionnaire's Disease

Legionnaires' disease is a type of pneumonia which can cause serious illness and death.

Legionella cannot be caught by drinking contaminated water; to be harmful the bacteria needs to be inhaled. So, while the risk of contracting the Legionella bacteria is very rare, some people are at higher risk, such as those who are over 50 years, smokers, and those with underlying health conditions.

Where can Legionella be found?

Wherever there is a water supply, there is the chance that legionella bacteria are present. They can be found in natural water sources like rivers, lakes and ponds.

They are also present in the artificial water systems in our homes and gardens such as:

• hot and cold-water systems and drinking water systems
• storage tanks
• pipes
• baths, taps and showers
• humidifiers
• fire fighting sprinklers and hoses
• garden hosepipes
• lawn sprinklers or watering systems

In the current coronavirus crisis, it is imperative that our health service is not put under any additional strain.

The Closure of buildings, parts of buildings or their restricted use, can increase the risk for Legionella growth in water systems and associated equipment including the above if they are not managed adequately. 

The bacteria grow in warm conditions and can multiply to a dangerous level if water in buildings has not been used for some time.

Water system maintenance regime

It is very important that while many buildings and offices are shut down due to the pandemic, that water systems are still well maintained to prevent future health issues like Legionella outbreaks.

As a general principle, outlets on hot and cold-water systems should be used at least once a week to maintain a degree of water flow and to minimise the chances of stagnation.

Closed buildings and reopening

To manage the risks during a period of closure, consideration should be given to commencing a flushing regime or other measures such as draining the system if the water system is to remain out of use for long periods.

Low risk premises such as offices that just have water supplied to kitchens and toilets can help prevent the build-up of Legionella by flushing through simple hot and cold-water systems with fresh mains water for several minutes.

Links to further information

Reopening Safely

For general information on reopening businesses safely please refer to the Chartered Institute of Environmental Health (CIEH) guidance, "Legionnaires' disease: lockdown risks and reopening safely"

Further Help

Training webinar for people in charge of buildings. An introduction into what to consider and practical advice on how to control Legionella. This presentation lasts for 45 minutes and has been produced by Vector Air and Water in support of the Chartered Institute of Environmental Health (CIEH).

The Health and Safety Executive provide information on flushing and draining systems in buildings left unoccupied for long periods of time.

Information on other water systems that are no longer in use, such as leisure, sports and swimming and spa pool facilities can be found in the Pool Water Treatment Advisory Group Code of Practice.

For further technical guidance on building water systems the European Society for Clinical Microbiology and Infectious disease has produced guidance on managing Legionella in building water systems during the COVID-19 pandemic.