Legionella Bacteria

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Legionella bacteria are common in natural water courses such as rivers and ponds. Since legionella are widespread in the environment, they may contaminate and grow in other water systems such as cooling towers and hot and cold water services.

They survive low temperatures (will over winter in water wet and damp conditions) and thrive at temperatures between 20-45°C if the conditions are right, e.g. if a supply of nutrients is present such as rust, sludge, scale, algae and other bacteria. They are however killed by high temperatures.

Under general health and safety law, employers have to consider the risks from legionella that may affect staff or members of the public and take suitable precautions. Employers or a person in control of the premises (e.g. a landlord), must:

• Identify and assess sources of risk;
• Prepare a scheme (or course of action) for preventing or controlling the risk
• Implement and manage the scheme – appointing a person to be managerially responsible, sometimes referred to as the ‘responsible person’
• Keep records and check that what has been done is effective
• If appropriate, notify the local authority must be notified if  a cooling tower(s) are on site

Anyone involved in the supply of water systems and their components (eg designers, manufacturers, water treatment companies and suppliers) has to make sure that such equipment is designed and made in such a way that it is safe to use at work and that it can be easily cleaned and maintained.

If you have a cooling tower or evaporative condenser on site you must, under the Notification of Cooling Towers and Evaporative Condensers Regulations, notify the local authority in writing with details of where it is located. You must also tell them when/if such devices are no longer in use. Notification forms are available from your local environmental health department.