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Legionella Risk Assessments

Assessments to identify and manage the risk of Legionella bacteria in water systems — a legal duty for landlords and businesses.

What is a Legionella Risk Assessment?

A Legionella risk assessment is an evaluation of the water systems in a property to identify conditions that could allow Legionella bacteria to grow and spread. Legionella bacteria can multiply in water systems where the temperature is between 20°C and 45°C, and where water is stagnant or there is a build-up of scale, rust, or organic matter.

The assessment involves a competent assessor inspecting the water system — including hot and cold water tanks, pipework, taps, showers, and any other water outlets. The assessor identifies any risks and recommends control measures to reduce them.

A written record of the assessment is produced, along with a recommended review date. For most residential properties, a risk assessment every two years is considered appropriate, though this depends on the findings.

Why is it important?

Legionnaires' disease is a severe form of pneumonia caused by inhaling water droplets contaminated with Legionella bacteria. It can be fatal, particularly in elderly people or those with weakened immune systems. Around 500 cases are reported in England and Wales each year, though many more go undiagnosed.

While large commercial water systems carry the greatest risk, domestic properties — particularly those with stored water tanks, complex pipework, or infrequently used outlets — can also present a risk. Properties left vacant for extended periods are especially susceptible to stagnation.

A Legionella risk assessment gives landlords and property managers clear, documented evidence that they have identified and addressed the risk — protecting tenants, and demonstrating due diligence.

UK Regulation

The duty to manage Legionella risk is set out in several pieces of UK legislation and guidance:

Health and Safety at Work Act 1974 — places a general duty on employers and those in control of premises to manage risks to health
Control of Substances Hazardous to Health (COSHH) Regulations 2002 — Legionella is classified as a biological agent, and its risks must be assessed and controlled
HSE Approved Code of Practice L8 (Legionella) — provides specific guidance on controlling the risk of Legionella in water systems
HSE HSG274 — technical guidance covering water systems in domestic and commercial premises

The HSE has confirmed that landlords have a legal duty to carry out a Legionella risk assessment for their rental properties. Failure to do so — particularly if a tenant contracts Legionnaires' disease — can result in significant legal and financial consequences.

Arrange a Legionella Risk Assessment

Get in touch with CZ Compliance and we will coordinate a competent assessor for your property.