What is a Legionella Risk Assessment and Why Should I Have One?

Legionella is hazardous bacteria that can be found in water. In a residential property, Legionella can grow in water stored at temperatures between 20°C and 45°C degrees. If ingested or inhaled, water containing Legionella will lead to Legionnaires’ disease or legionellosis – an infectious and sometimes fatal form of pneumonia.

Hot and cold water systems are an ideal environment for Legionella to grow in. The risk of contamination is particularly higher in:

• Water tanks and systems in which water is stagnant and/or recirculated
• Temperatures between 20°C and 45°C degrees
• Water droplets or aerosols produced by whirlpool baths or showerheads
• Mist and spray dispersed into the air
• Rust, scale, sludge and biofilm that “feed” the bacteria
• Properties that are left empty for long period of time

The risk of Legionella is particularly low in properties with combi boilers, as the system keeps the water moving – giving the bacteria little chance to develop.

However, homes with open water tanks (usually older buildings) have a substantially higher risk of Legionella, as the water is more likely to be left to stagnate.

A Legionella risk assessment is a formal inspection and evaluation of a building's water systems to identify conditions that could lead to the growth and spread of Legionella bacteria, which cause Legionnaires' disease. The assessment involves examining water system components like tanks, pipework, and outlets for hazards such as stagnant water or inadequate temperatures, and then recommending control measures, such as temperature control, cleaning, and regular monitoring, to mitigate these risks.

There is a legal duty for landlords to assess and control the risk of exposure to legionella bacteria, but they are not required to conduct a professional assessment or test.

Whilst testing is part of a professional Legionella risk assessment, Health and safety law does not require landlords to test their water systems produce or obtain ‘Legionnaires testing certificate’.

HSE Myth Busters: Landlord’s Responsibilities Regarding Legionella Risks

Landlords in Scotland are legally required to have a Legionella Risk Assessment.

Landlords in England and Wales are not legally required to produce a formal certificate in the same way they are expected to have an EICR, EPC or Gas Safety Record.

However, landlords do have a more general legal duty of care to protect the health and safety of their tenants – a part of which is to ensure their property’s water is safe to drink and use.

To do this, landlords can have a 'Risk Assessment'  carried out. A professional risk assessment is not a formal legal requirement, however, it’s a good way to ensure your water supply is safe.

It is also strongly recommended in the government’s How to Let guide - more information on this can be found on our 'legal bits' page.

For rental properties with water systems that could pose a potential Legionella risk, it is recommended that a Legionella risk assessment is carried out once every two years – or before a new tenancy begins. It’s also a good idea to perform a risk assessment if there are significant changes to the property’s water systems.