Legionella advice

This guide explains what legionella is and what you can do to reduce the risk to you and your family.


What is legionella?

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

Water temperatures of 60C and above will kill legionella bacteria. The bacteria can live and multiply in low water temperatures, between 20C and 45C. Legionella is most likely to be found where there is stagnant water and a supply of nutrients, such as rust, sludge, scale, algae or other bacteria.

How might legionella be harmful?

Legionella bacteria can cause a form of pneumonia called Legionnaires’ disease, as well as other less serious illnesses.

How do people get Legionnaires’ disease?

People catch Legionnaires' disease by breathing in air containing the bacteria. The bacteria would not be visible as it can be formed from fine droplets suspended in the air, produced by running a tap or shower, or flushing a toilet.

You can’t get Legionnaires’ disease from drinking water and it can’t be passed from one person to another.

What are the symptoms?

Not everyone who comes into contact with legionella bacteria becomes ill.

Everyone is potentially vulnerable to infection caused by breathing in legionella bacteria, but some people are at higher risk. Those at higher risk include smokers, heavy drinkers, and people over 45 years of age, suffering from chronic respiratory or kidney disease, or a weakened immune system. The symptoms of Legionnaires' disease are similar to the symptoms of flu:

  • high temperature;
  • fever and chills;
  • a cough;
  • muscle pains; and
  • headaches.

In severe cases, there may also be pneumonia and, occasionally, diarrhoea, as well as signs of mental confusion.

If you suspect that you or someone in your home has contracted Legionnaires’ disease, you should contact your doctor as soon as possible. If your GP diagnoses Legionnaires’ disease, contact us immediately so that water analysis and any necessary treatment of your water system can take place.

How to reduce the risk of legionella in your home

The likelihood of legionella being present in your home is very low. Most households don’t store much water and they use water regularly so it’s not standing still in pipes and tanks.

However, there are some simple steps you can take to help prevent the bacteria growing.

  • Keep your hot water cylinder thermostat set at 60C to kill any legionella bacteria. Remember to mix hot water at this temperature with cold water or leave it to cool before bathing to prevent scalding.
  • Descale shower heads at least every three months and keep hoses free from a build-up of limescale, mould or algae. If the shower hose shows signs of blocking, clear this straight away. Any domestic descaling solution that you can buy from a supermarket or hardware shop suitable for descaling your iron or kettle can be used, but please make sure you read the label and follow any safety instructions. After descaling, flush the shower thoroughly, then soak the shower head and/or hose in bleach. This will help sterilise and kill any bacteria.
  • Clean your taps regularly. Brush the scale away from all surfaces, including any spray inserts, with a nylon brush or wipe them with a domestic descaling solution.
  • If you go on holiday or leave your property for a week or more, when you come back, flush your toilets with the lid down and run all taps and showers continuously for about two minutes to flush out any bacteria. You should run the water slowly for a few seconds to avoid spray, before running the water faster. When you’re running the shower, you should hold the shower head directly over the plughole.
  • Run garden hoses into a drain or unused area of your garden, for one minute before you use them.
  • Keep water butts clean and don’t use them to supply a pumped device.
  • If you have a water tank, make sure that the lid is tight-fitting to prevent contamination, and check that the tank insulation is fitted correctly.
  • Report any deposits such as rust or any unusual matter flowing from your taps to us.
  • Let us know if the hot water is not heating properly or if there are any other problems with the system.

More information

The Health and Safety Executive is the government body responsible for water hygiene and Legionnaires’ disease. You can find further advice and information on their website: www.hse.gov.uk/legionnaires

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