Management of workplace water systems to prevent Legionnaires Disease

Posted on: Thu, 08/04/2021 by Encompass Safety Solutions | Health & Safety

The Management of Health & Safety at Work Regulations (1999) includes a legal requirement for employers to conduct various workplace risk assessments.  One of the key areas that requires regular risk assessment is the management of hot and cold-water systems.  Workplace water systems can provide favorable conditions for the growth of legionella bacteria, the root cause of Legionnaires Disease.

Legionnaires Disease is a potentially fatal form of pneumonia caused by the inhalation of contaminated water droplets infected with the bacteria, which can grow in all forms of water systems and thrives on systems containing rust, sludge, scale, biofilms, plant matter and other nutrients to feed it.

Conducting regular risk assessments

Business owners need to ensure that their water systems are checked regularly, both for the presence of the bacteria and contaminants that the bacteria can feed on. 

For most cold water systems, the bacteria can controlled by ensuring the temperature at all cold water outlets (taps and showers) is below 20 degrees Celsius.  This ensures that the bacteria, if present, are kept dormant.  Hot water systems should store water at the highest temperature available by turning the thermostat to its maximum, or at least 60 degrees Celsius.  At sixty degrees Celsius or higher, the legionella bacteria are killed almost instantly.  Storage at high temperatures also ensures that hot water reaches the outlets of 50 degrees Celsius or more, killing the bacteria within an hour or two.

Storing or using water in the ‘danger zone’ of between 20-45 degrees Celsius increases the risk of bacteria proliferation, and if the water droplets, or aerosol, is inhaled, contracting legionellosis (legionnaires disease) is a very real risk.

Implementing simple measures such as temperature management, whether hot or cold, and keeping the water moving are highly effective in minimising the risk.

Other measures can include:

  • Regular water system flushes.
  • Regular chlorination of any storage tanks and cleaning of areas around tanks to prevent debris from building up.
  • Checking and setting temperature controls.
  • Checking and removing any pipes or system parts that are no longer in regular use.  Removal of ‘dead legs’ and ‘little-used’ outlets minimises the risk of water standing still for long periods of time and stagnating, which gives the bacteria a food source.

Encompass Safety Solutions offers numerous cost-effective legionella risk assessment services, including full system checks and bacteriological sampling for water systems, ensuring that you keep your hot and cold water systems safe.

To find out more about our legionella risk assessment services, contact us today on 0845 017 9866 or email


Management of workplace water systems to prevent Legionnaires Disease
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