Legionella risk assessments: who needs one and why it matters

Legionella bacteria is a silent threat in many water systems. While it’s naturally occurring, if conditions are right, it can grow rapidly, and cause serious health risks like Legionnaires’ disease. That’s why Legionella risk assessments are a legal requirement in many settings.

But what is a Legionella risk assessment exactly? And is it something all landlords or business owners need to arrange?

In this guide, we’ll cover everything you need to know from your legal duties to what’s actually included in an assessment.

What is a Legionella risk assessment?

A Legionella risk assessment is a structured review of a property’s water system to identify any risks associated with Legionella bacteria. The goal is to find areas where bacteria could grow or spread, and then take steps to reduce or eliminate those risks.

It typically involves:

• Surveying cold and hot water systems
• Checking water temperatures and flow
• Identifying pipework dead legs or low-use outlets
• Inspecting storage tanks, taps, and showers
• Assessing current maintenance and monitoring practices

The assessment must be carried out by someone competent either an internal facilities manager or an external specialist trained in water hygiene. A detailed report is then produced with findings, control measures, and an action plan.

Is a Legionella risk assessment mandatory?

Yes. In most cases, a Legionella risk assessment is a legal requirement under UK health and safety law. Specifically, it’s covered by:

• The Health and Safety at Work Act 1974
• The Control of Substances Hazardous to Health (COSHH) Regulations 2002
• The Approved Code of Practice (ACoP) L8

Under these regulations, duty holders (including landlords, building owners, and employers) must assess and control the risk of exposure to Legionella bacteria.

If you’re wondering, “is a Legionella risk assessment mandatory?” the short answer is yes, unless your system is so low-risk that a competent person can demonstrate otherwise (which is rare).

Even in small residential settings, such as rental flats or HMOs, landlords must carry out a basic risk assessment and keep a written record.

Who is responsible for arranging it?

The duty holder is responsible, this might be:

• A building owner or landlord
• An employer or facilities manager
• A responsible person appointed by the business

In rented properties, landlords are legally required to ensure water systems are safe. This includes managing hot water cylinders, cold-water tanks, pipes, showers, and taps.

For commercial and public buildings like offices, hospitals, gyms, and schools, the responsibility falls to building managers or duty holders. In most cases, it's advised to hire a professional to carry out the assessment and help put a water safety plan in place.

If you need help meeting your obligations, our team offers professional legionella risk assessment London services across a wide range of sectors.

What happens if you don’t do it?

Failing to carry out a Legionella risk assessment can lead to:

• Legal penalties or fines
• Prosecution in the event of illness or exposure
• Invalid insurance claims
• Loss of reputation or trust from tenants and staff

In severe cases, outbreaks of Legionnaires’ disease have resulted in business closures and criminal investigations. Keeping on top of your water hygiene duties is a basic but crucial part of building safety and compliance.

What’s included in a proper assessment?

A professional Legionella risk assessment includes:

• Visual inspection of water tanks, pipes, and fixtures
• Temperature checks at outlets and tanks
• Identification of stagnation or dead ends in pipework
• Review of maintenance records and control measures
• A full written report with recommendations
• A risk rating and required actions (e.g. flushing, cleaning, upgrading systems)

The report should also assign responsibility to specific individuals, outline inspection frequencies, and set up a regular review schedule.

How often should it be done?

There is no set legal frequency, but best practice is:

• Every 2 years for low-risk systems
• Annually for moderate to high-risk systems
• Immediately after significant changes to the water system

Regular reviews ensure that any changes in usage, layout, or system performance don’t introduce new risks. Even if your water system seems low-risk, periodic checks help confirm that.

Do landlords need to test water?

Generally, testing for Legionella isn’t mandatory unless your assessment identifies a specific risk. In domestic settings, simple control measures, like keeping water hot, flushing unused taps, and regular maintenance, are often enough.

However, in commercial or high-risk environments, routine sampling may be recommended.

If you're unsure whether your system needs testing, our legionella risk assessment London experts can advise on what's necessary for your site.

Final thoughts

Legionella risk assessments are a legal requirement and a key part of responsible water management. Whether you're a landlord with a few properties or a facilities manager of a large commercial site, staying compliant protects your tenants, staff, and business.

If you’re unsure about your legal duties or need help carrying out an assessment, speak to a certified provider today. Getting it done right not only meets regulations, it also gives peace of mind.

Need help with a Legionella risk assessment?

We provide trusted legionella risk assessment London services for landlords, commercial properties, and facility managers. Our expert team ensures your building is compliant, safe, and fully documented.

Contact us today to book your risk assessment

References

LegionellaDossier – Everything About Legionella Risk Assessments 

LegionellaControl.com – Do Landlords Need to Do a Legionella Risk Assessment?

HSE – Legionella and Landlords' Responsibilities