What is Legionnaires' disease?
Legionnaires' disease is a potentially fatal form of pneumonia caused by breathing in small droplets of water that contain legionella bacteria. It is not passed from person to person and you cannot catch it by drinking water. Related, milder illnesses caused by the same bacteria are Pontiac fever and Lochgoilhead fever. Together they are known as legionellosis.
Where does legionella grow?
Legionella bacteria multiply in water between about 20°C and 45°C, especially where water is stagnant and there is something for the bacteria to feed on, such as scale, sludge, rust, biofilm or organic matter. Common risk areas include:
- Hot and cold water systems in all kinds of buildings
- Cold water storage tanks, particularly uncovered or poorly insulated ones
- Little-used showers, taps and hoses
- Dead legs and redundant pipework
- Cooling towers and evaporative condensers
- Spa pools and hot tubs
- Thermostatic mixing valves and the pipework downstream of them
Who is most at risk?
Anyone can catch Legionnaires' disease, but some people are at much higher risk, including people over 45, smokers and heavy drinkers, people with chronic respiratory or kidney disease, diabetes or heart disease, and anyone with a weakened immune system. That is why care homes, hospitals and healthcare premises need extra controls.
How is legionella controlled?
The core controls are simple and are set out in HSE's Approved Code of Practice L8 and its technical guidance HSG274:
- Keep hot water hot. Store it at 60°C or above and distribute it so it reaches at least 50°C at outlets within one minute (55°C in healthcare premises).
- Keep cold water cold. Cold water should be below 20°C within two minutes of running.
- Keep water moving. Flush little-used outlets at least weekly and remove dead legs.
- Keep systems clean. Inspect tanks, descale shower heads and service TMVs.
What the law expects
If you are an employer, a landlord or otherwise in control of premises, you must identify and assess the risk from legionella, put controls in place, keep records and appoint a competent person to oversee it. Our legionella risk assessment is the first step.
Frequently asked questions
Can you get Legionnaires' disease from drinking water?
No. Infection happens when contaminated water droplets or spray are breathed in. Aspiration can occasionally be a route in vulnerable patients.
What temperature kills legionella?
Legionella stops multiplying above about 50°C and dies quickly at 60°C and above. That is why hot water storage at 60°C is a key control.
Disclaimer: This guide is general information about UK requirements and is not legal advice. Always check the current legislation and guidance for your premises.