At some point you have likely seen a headline about an outbreak of legionnaires’ disease. But you may not have explored the source of any outbreaks and therefore be unaware of what this illness is and how it is contracted.
While outbreaks are rare, it’s important to understand what you can do to prevent legionella bacteria from growing, especially if you are managing a property that is home to or frequented by those at high risk of contracting the illness.
What is legionella and legionnaires’ disease?
Legionella is a waterborne bacteria that occurs naturally in fresh water. There are several types of legionella bacteria, of which one (legionella pneumophila) is most likely to cause an outbreak of legionnaires’ disease.
Legionnaires’ disease can develop in people who have been exposed to this strain of legionella bacteria. It is a serious form of pneumonia that can cause serious illness and even death.
You can contract legionnaires’ disease by inhaling airborne water droplets that contain a viable form of the bacteria.
Because this bacteria is present in fresh water, it can find its way into our heating and plumbing systems. However, for the bacteria to develop to a point where it can cause illness, it will need specific conditions.
For instance, legionella is dormant at temperatures below 20 degrees C and cannot survive in temperatures over 60 degrees C. It is most likely to multiply to harmful levels in water that is kept at between 20 and 45 degrees C.
How long does legionella take to develop in water?
If the conditions are right, legionella bacteria can grow to harmful levels in just a few days. This is why it is important to test for legionella regularly and to ensure that your heating and water system is designed to minimise the risk of the bacteria proliferating.
Once someone is infected with legionella bacteria, it can take between two and ten days for symptoms of legionnaires’ disease to appear.
Do you have to test for legionella?
In some premises, you will need to test for the presence of legionella in your heating and plumbing system regularly throughout the year. This applies to certain types of systems in particular, namely open systems like cooling towers, evaporative condensers and spa pools.
Your risk assessment for legionella will also dictate whether you need to carry out regular testing and at what intervals.
If you are managing the heating and plumbing system for a building where at-risk groups either live or spend time, you may need to carry out regular testing too.
This typically applies to buildings such as care homes, residential homes and hospitals.
It’s important that your legionella testing is carried out by a competent person who is trained to identify the conditions that are likely to lead to the growth of this kind of bacteria. If regular testing is part of your risk assessment, find a legionella testing company in your area to support you.
However, most water systems are enclosed, which means they are not exposed to the elements, which makes an outbreak of legionella much less likely. This also means regular testing won’t be necessary unless you suspect one of the control measures isn’t working.
What is a legionella risk assessment?
A legionella risk assessment explores the risk of legionella developing in your system, as well as the potential consequences of it doing so.
You will need to consider the risk of legionella if you manage a property, whether as a landlord or as an employer.
A risk assessment for legionella is like any other risk assessment. You need to work out the likelihood of an outbreak occurring and specify what measures you will take to minimise that risk.
What can you do to prevent legionella in your heating system?
The good news is there are some simple steps you can take to ensure your heating and water system is set up to minimise exposure to legionella bacteria. These include:
- Using temperature control for both hot and cold water.
- Keeping your water system clean.
- Ensuring the design of your heating and water system reduces the risk of legionella growing.
Temperature control
One of the most effective ways to prevent legionella bacteria from growing is to keep the temperature of your water at levels that don’t support the bacteria.
This means cold water should be stored below 20 degrees C, and your hot water needs to be stored at temperatures of 60 degrees C or higher, while also being distributed at a minimum of 50 degrees C.
Cleaning your water system
Stagnant water is a breeding ground for bacteria, including legionella, so keeping your water system clean and moving is important to prevent it from growing.
One of the simplest steps you can take is to ensure that outlets, like taps, toilets or showers, that aren’t used frequently are regularly flushed out. This involves running the water outlet for between two and five minutes to remove all the stagnant water.
Heating and water system design
Removing any unused pieces of pipework and getting rid of unnecessary water storage can all help reduce the risk of legionella bacteria growing. Appropriate insulation for both pipes and water tanks is also important for maintaining temperature control.