What is Legionella?
Legionella is a bacterium commonly found in water and can cause Legionnaires' disease, a lung infection similar to pneumonia that can be fatal. The Legionella bacteria multiply in temperatures between 20°C and 45°C, where nutrients are available. The bacteria are dormant below 20°C and do not survive temperatures above 60°C.
Legionnaires' Disease
Legionella bacteria can cause Legionnaires’ Disease and are contracted by inhaling airborne water droplets and vapours that contain the bacteria. This can come from sources such as hot and cold water outlets, showers and spray taps, hydrotherapy baths and whirlpools, and even some air conditioning units.
Anyone can contract Legionnaires’ Disease, but the elderly, smokers, people with respiratory problems, kidney disease and cancer are more at risk. However, it is not contagious and cannot be spread from person to person.
Health and Safety Requirements
For health and safety, healthcare and education facilities must have water management checks in place. It is also advisable to have checks in place for businesses such as offices. For more detailed advice on Health and Safety requirements, visit www.hse.gov.uk.
Water storage and temperature control
One of the best ways to control the risk of Legionella is to check and maintain the temperatures of your water storage and water outlets.
Hot Water Storage Heaters should store water at 60°C or higher. However, hot water should be distributed at 50°C or higher. Where there is a risk of scalding, thermostatic mixing valves should be fitted as close to the water outlet as possible.
All cold water should be both stored and distributed at 20°C or lower. 'Sentinel’ outlets are the closest and furthest away from your water storage, and they need to be temperature-checked once a month to ensure they are distributing water at the correct temperatures. If you have a hot water storage cylinder, this also needs to be checked each month, whereas cold water storage tanks only need to be checked every six months. Below is an easy checklist to guide you, outlining the checks that need to be done and how often they should be performed.
Weekly Checks
- Outlets that are infrequently used – once a week or less – need to be flushed through. This includes taps, showers and hoses.
Monthly Checks
- Your ‘sentinel’ outlets need to be checked and have the temperature recorded. Record the temperature of the hot water after 1 minute of operation and the cold water temperature after 2 minutes of operation. Your hot water storage tank or calorifier water heater also needs to be checked and have its temperature recorded.
Quarterly Checks
- All showerheads and hoses should be dismantled, cleaned and descaled. This should be recorded.
Six-monthly checks
- Your cold water storage tank temperature needs to be checked, recorded, and also inspected for any debris or corrosion.
Annual Checks
- At least once a year, all water outlets should be checked for their distribution temperature and also inspected for corrosion and deterioration. In some establishments, a drain sample may also be required to be sent off for testing. For more detailed advice, please visit www.hse.gov.uk.
Additional Safety Measures
To further reduce the risk of Legionella, you can fit water tanks with secure lids and insect screens. Keep pipework as straight and direct as possible and remove any ‘dead legs’ from your system – those bits of pipework that have a dead end. It is also worth checking that your pipework, where necessary, is well insulated.
Modern technology can also help. Consider installing an Anti-legionella thermal mixing valve (TMV).
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