It is important for businesses and buildings to have a Legionella risk assessment to test their water hygiene, and for the potential threat of Legionella within their water systems.

Having a Legionella risk assessment done is not only taking the first step towards a safe and healthy workplace but also allows you to stay ahead of proper legislation.

Below is everything you need to know about Legionella, and what is expected of you when it comes to a potential assessment.

What is Legionella?

It is a specific type of bacteria genus that is caught through the inhalation of water droplets that have been through infected water systems.

It is caused by several factors including:

  • The bacteria will grow between 20 degrees celsius and 40-50 degrees celsius. It thrives off of this particular temperature environment.
  • If your water is stagnant, the bacteria is more likely to develop and spread. Clean, flowing water will help to deter this growth.
  • It thrives off of collections of organisms such as rust or sludge to spread, so maintaining clean water systems is vital.

Inhaling this bacteria can cause Legionnaires disease, which can be potentially fatal in many cases.

How can Legionella be harmful?

Legionnaires disease is a severe form of pneumonia that can affect the lungs to a potentially fatal degree.

It is caused by the inhalation of droplets that contain Legionella bacteria that has grown within water systems. Other Legionella risks are Pontiac fever and Lochgilphead fever, which are less serious but more common infections.

Exposure to Legionella is especially harmful to those at a higher level of risk such as:

  • Heavy smokers
  • Those with respiratory diseases
  • Those with lung and heart disease.

Prevention is caused by good maintenance within your water systems, and regular risk assessments and testing.

Temperature regulation
Water Systems Dosing

Why Choose ARA?

Why Legionella risk assessments are important

They are important because they help to identify all water systems that could potentially have a risk of Legionella including, but not limited to:

  • Hot and cold water systems
  • Sprinklers
  • Cooling water systems
  • Spa pools
  • Fountains

Risk assessments allow you to put Legionella control measures in place, such as making sure the water temperature for your system is adequate.

Having these risk assessments also stops those who are particularly susceptible to Legionnaires disease, such as those who have specific health conditions that make them more high risk, from contracting it.

What to expect during a legionella risk assessment

Not all risk assessments are the same, but several main points are:

  • A check of your previous risk assessment, ensuring that all areas that needed to be acted on have been.
  • A tour in which all of your water sources and systems are assessed.
  • Temperature recording, to make sure that your systems are staying at the right temperature.
  • A report assessing your risk of the bacteria.
  • Recommendations for the future about how best to control the risk of Legionella.


Yes – to ensure that any risks are seen and that specific actions are taken to control the risk of infection and that the water system is back to appropriate conditions.

However, landlords do not need to provide proof of a Legionella test certificate, just that a risk assessment has been carried out.

Reviewed every two years at least, but needs to be assessed regularly when you are able. You definitely need to assess your system sooner if you have reason to believe there could be a risk of exposure to Legionella that has come from where your water is stored.

If you are a landlord or are in charge of the health and safety legislation of your company, then you should always make sure that your Legionella risk assessments are carried out by a competent water hygiene specialist.

Legionella control measures should be put in place to make sure the bacteria doesn’t spread and lead to infection.

Yes- it is a requirement that all landlords need to assess the risks of legionella in water tanks and pipes within their residencies. Landlords of single dwellings can perform this risk assessment themselves if they have the right awareness training.

However, if landlords do no possess this then they should always hire a professional to carry out their risk assessments for them. Tests are not mandatory, but they do need to assess the risk of Legionnaires disease from water sources.

A risk assessment should be done, at the very least, every 2 years.

However, you should have a regular risk assessment carried out on your water quality and specifically the areas that could be considered a breeding ground for Legionella bacteria, or if you have sufficient cause.

If you’re a landlord, or are in charge of the health and safety of your site and have appropriate risk awareness training, then you can carry out a risk assessment on your water system by yourself.

Other than that, anyone else will need to hire a professional assessor who can identify areas with high and low risk and provide an effective and fair assessment of your water system.

This will help you control the risks of the bacteria growing with your water system and bring down the rate of potential future infections.