Legionella (water systems)

What is Legionnaires' Disease?

Legionniares' Disease is one of a group of diseases collectively known as legionellosis.  It is caused by the bacterium Legionella pneumophila and of the group can be the most serious, creating a potentially fatal form of pneumonia.  The disease can affect anybody, although principally affects those who are susceptible because of age, illness, immune-suppression, smoking etc.

Where is it found?

The bacteria is widespread in natural sources of water including rivers, streams and ponds and may even be found in soil.  It can also be found in many recirculating and hot and cold water systems.  The bacteria especially thrives at temperatures between 20-45C and if the conditions are right, for example a supply of nutrients such as rust, sludge, scale, algae and other bacteria are present.

Why aren't there more outbreaks?

A specific chain of events has to occur before people can become infected by the legionella bacteria.  This includes:  conditions that enable the organism to multiple; a means of creating breathable droplets and finally contact with the contaminated droplets by a susceptible person.  

What are the legal duties?

Although legionella is not covered by its own specific set of Regulations, the general duties under the Health and Safety at Work etc Act, and the Control of Substances Hazardous to Health Regulations (COSHH) which requires employers to ensure the risk of exposure to substances hazardous to health, including legionella  which is classed as a biological agent under COSHH are assessed and controlled, apply. 

The Health and Safety Executive have also recognised the specific risks from legionella with the production of L8: The Control of Legionella Bacteria in Water Systems Approved Code of Practice which outlines specific arrangements employers and those responsible for premises should follow to prevent and / or control the risk of exposure to the legionella bacteria.

As such, to ensure compliance the University operates under the University Policy Water Safety Management (Legionella). In addition, Campus Services has appointed a specialist contractor to monitor the condition of water and water services and others as necessary to oversee water systems, with regards to tests, inspections, maintenance and the suitability of the design of modified and new systems. 

For Colleges, Schools and Services a guidance document is available, which summarises the challenges associated with equipment which holds or delivers water and offers practical steps to help you manage the risks.

How can the risk be reduced?

As legionella naturally occurs in the environment, it cannot be prevented from entering water systems.  However, the risk of an outbreak developing can be reduced by taking the following precautions:

Hot and cold water systems:

  • Cisterns and pipe work should be designed so that water is not allowed to stand, undisturbed for long periods of time.
  • Cisterns should be covered to prevent the entry of dirt, debris, vermin and should be periodically inspected, cleaned and disinfected.
  • Water temperatures between 20C and 45C should be avoided by insulation of cold water tanks and pipes in warm spaces, and by storing hot water at 60C and circulating water at 50C. 
  • Only specific fittings and materials should be used which do not support the growth of bacteria.

Cooling towers / evaporative condenser (there are none at the University):

  • Specific design, treatment and maintenance requirements must also be followed for cooling towers.
  • In addition, any person in control of a premise which contains a wet cooling tower / or evaporative condenser must be notified to the Local Authority, Environmental Health Department.

Further information:

Additional information can be found on the Legionnaires' disease section of the or contact HSS