Legionella risk assessments are a legal and practical requirement for anyone who controls a building’s water systems in the UK. If you’re a landlord, employer or facilities manager, you are the duty holder and must ensure a suitable and sufficient Legionella risk assessment is carried out, kept up to date, and supported by effective control measures, in line with ACOP L8 and HSE guidance.
TL;DR
- A Legionella risk assessment is legally required wherever people could be exposed to Legionella bacteria from water systems (workplaces, rental properties, commercial premises).
- Duty holders include employers, landlords, building owners, facilities managers and anyone in control of premises and water systems.
- ACOP L8 and HSG274 set out how to control Legionella: assess risk, appoint competent people, implement a written scheme of control, monitor, keep records and review regularly.
- Landlords must assess and control Legionella risks in rental properties, even if the assessment is simple and proportionate for low-risk domestic systems.
- A Legionella risk assessment involves surveying water systems, identifying hazards, assessing who could be exposed, recommending control measures and documenting everything.
- Risk assessments must be reviewed regularly and whenever the system, building use or risk profile changes (for example, refurbishment, change of occupancy, new plant).
- Common failures include treating a single assessment as “job done”, poor record keeping, and not providing Legionella training for responsible staff. These can all lead to enforcement action and increased health risks.
- Legionella prevention focuses on temperature control, good system design, flushing, cleaning, maintenance, and consistent monitoring.
- Training is critical. Competent duty holders and responsible persons are expected to understand their legal duties and how to apply ACOP L8 and water hygiene best practice in the real world.
What Is a Legionella Risk Assessment?
A Legionella risk assessment is a structured review of your water systems to identify where Legionella bacteria could grow and how people might be exposed. It looks at system design, operating conditions and usage patterns, then sets out the measures needed to prevent or control risk.
Legionella bacteria thrive in man‑made water systems that provide the right conditions. These conditions include stagnant water, suitable temperatures (20-45°C), nutrients and aerosol generation. Showers, cooling towers, hot and cold water systems and decorative fountains are all common examples.
The purpose of a Legionella risk assessment is to:
- Identify potential sources of Legionella growth within the water system.
- Determine who might be at risk, including vulnerable users.
- Recommend proportionate control measures to minimise risk.
- Support ongoing water safety management and legal compliance.
Carrying out a suitable and sufficient Legionella risk assessment is a legal duty under general health and safety legislation and associated regulations; the requirement is operationalised through ACOP L8 and HSG274 guidance.
What Does a Legionella Risk Assessment Involve?
A competent Legionella risk assessment typically includes:
- Inspecting water systems – mapping hot and cold water systems, storage tanks, pipework, outlets, and any other aerosol‑generating equipment.
- Identifying risk factors – dead legs, low‑use outlets, inappropriate temperatures, poor insulation, scale, corrosion or contamination.
- Assessing vulnerable users – elderly residents, immunocompromised individuals, healthcare patients or others at higher risk from Legionnaires’ disease.
- Recording findings – producing a clear report, schematics and asset register, with a written scheme of control where needed.
- Recommending control measures – temperature control, flushing, cleaning, design changes, monitoring regimes and maintenance.
The assessment should be proportionate to the size and complexity of the system. A small office or domestic rental property may need a relatively simple assessment, while a hospital hot water system or industrial plant requires a far more detailed approach.
Why Risk Assessments Matter
There are four main reasons Legionella risk assessments are essential:
- Health protection – Legionnaires’ disease is a serious, potentially fatal pneumonia. Proper risk assessment and control help prevent outbreaks and protect occupants.
- Legal compliance – UK health and safety law requires duty holders to identify and assess risks from Legionella and to implement controls. Failure can lead to enforcement notices, fines or prosecution.
- Effective water management – understanding your systems and risks leads to better design, maintenance and operation, often improving efficiency as well as safety.
- Demonstrating due diligence – a documented, up‑to‑date assessment and control scheme show regulators, insurers and courts that you have taken reasonable steps to manage risk.
What Are the L8 Regulations?
When people talk about “L8 regulations”, they are usually referring to ACOP L8: Legionnaires’ disease: The control of Legionella bacteria in water systems, published by the Health and Safety Executive (HSE).
ACOP L8 is not a standalone law, but it has special legal status. It explains how to comply with existing health and safety legislation in relation to Legionella, including:
- Health and Safety at Work etc. Act 1974
- Management of Health and Safety at Work Regulations 1999 (MHSWR)
- Control of Substances Hazardous to Health Regulations 2002 (COSHH)
Understanding ACOP L8
ACOP L8 sets out the core duties for duty holders and responsible persons:
- Identify and assess risk – ensure a suitable and sufficient Legionella risk assessment is carried out for relevant water systems.
- Appoint competent people – identify a duty holder and responsible person with adequate knowledge, training and authority.
- Develop a written scheme of control – define how risks will be prevented or controlled: temperature regimes, inspections, cleaning, monitoring and corrective actions.
- Implement and monitor controls – carry out checks, measurements and maintenance in line with the scheme.
- Keep records – maintain records of the assessment, monitoring, inspections and test results, typically for at least five years.
- Review regularly – reassess and update the risk assessment and control scheme when circumstances change or at defined intervals.
Following ACOP L8 is usually regarded as sufficient to comply with the law; if you depart from it, you must be able to show you achieved equivalent control in another way.
Supporting Guidance Documents
ACOP L8 is supported by detailed guidance in HSG274, which is split into parts covering different systems:
- Part 1 – cooling towers and evaporative condensers.
- Part 2 – hot and cold water systems in buildings.
- Part 3 – other risk systems (e.g. spa pools, humidifiers, industrial systems).
HSG274 explains what a Legionella risk assessment should consider, outlines typical hazards, and provides examples of maintenance and monitoring regimes for different types of system.
This guidance is widely recognised as industry best practice, and many organisations base their policies and procedures directly on L8 and HSG274.
For those involved in broader water regulations, Logic4training’s Water Regulations training course can help you understand how Legionella control fits within wider water hygiene regulations.
Why Compliance Is Important
Compliance with ACOP L8 and HSG274 is important because:
- It shows you are meeting your legal obligations under health and safety law.
- It clarifies your health and safety responsibilities, particularly where multiple parties are involved (e.g. landlords and managing agents).
- It provides evidence of due diligence if an incident occurs, helping to show that you took reasonable steps to manage risk.
Ignoring L8 or treating it as optional exposes duty holders to real risk: both to people’s health and to organisational reputation, finances and regulatory relationships.
Who Is Responsible for a Legionella Risk Assessment?
The key question many building controllers ask is: who is legally responsible for Legionella?
Under UK health and safety law, the primary duty falls on those who control premises and associated water systems. In practice, that includes:
Duty Holders Under Health and Safety Law
Duty holders typically include:
- Employers control workplaces and employees’ exposure to water systems.
- Building owners are responsible for the premises, plant and infrastructure.
- Facilities managers and managing agents where contracts give them control over maintenance and safety checks.
- Responsible persons are individuals appointed to oversee Legionella compliance on behalf of the organisation.
If multiple parties are involved, the management contract or agreement should clearly specify who has responsibility for Legionella risk assessment and control. If not, the duty usually sits with the person or organisation in control of the premises and water systems.
Landlord Responsibilities
Landlords who rent out property, including rooms in their own homes, have a legal duty of care to ensure their properties are safe and free from health hazards. This duty includes assessing and controlling the risk from Legionella in domestic water systems.
For landlords, this means:
- Carrying out a Legionella risk assessment for rental properties that is proportionate to the property’s risk profile.
- Taking reasonable precautions to prevent Legionella growth, such as keeping hot water hot, avoiding stagnation and maintaining systems.
- Ensuring that tenants’ exposure to aerosols (for example from showers) is adequately controlled.
HSE guidance acknowledges that many domestic properties are relatively low risk and do not require complex, in‑depth assessments, but the duty to assess and control risk still exists.
Responsibilities in Commercial Buildings
In commercial premises, responsibilities are often more complex, but the underlying principle is the same: the duty lies with those in control of the building and its systems.
This includes:
- Offices and workplaces – employers and building owners must ensure workers and visitors are protected.
- Hotels and leisure facilities – owners and operators must manage showers, spa pools and other higher‑risk systems.
- Healthcare settings – hospitals, clinics and care homes must follow strict water safety management protocols due to vulnerable patients.
- Educational facilities – schools, colleges and universities must consider Legionella risk in changing facilities, sports buildings and accommodation.
- Industrial premises – plant owners and operators must assess complex systems and any aerosol‑generating processes.
In all cases, a clear assignment of responsibility, backed by Legionella training and competent advice, is essential.
What Does a Duty Holder Need to Do?
Once you know you are the duty holder, the next step is understanding what you actually need to do. ACOP L8 and HSG274 set out a series of practical duties.
1. Identify Risks
Duty holders must ensure that a suitable and sufficient Legionella risk assessment is carried out, covering:
- Water storage such as cold water storage tanks, calorifiers, cylinders and any other stored water.
- Pipework, including distribution networks, including long pipe runs, dead legs, little‑used outlets and redundant branches.
- Cooling systems such as cooling towers and evaporative condensers are present.
- Little‑used outlets such as guest rooms, infrequently used showers, external taps and other outlets prone to stagnation.
This process should identify where Legionella could grow and how people could be exposed via aerosols.
2. Implement Control Measures
Where risk is identified and cannot be eliminated, duty holders must implement Legionella control measures that are proportionate to the level of risk.
Typical measures include:
- Temperature control – keeping stored and circulating hot water at appropriate temperatures and ensuring cold supplies remain sufficiently cool.
- Flushing regimes – regularly flushing little‑used outlets to prevent stagnation.
- Cleaning and disinfection – periodic cleaning of shower heads, tanks, pipework and other components to control biofilms and scale.
- Monitoring – checking temperatures, system performance and, where appropriate, microbiological parameters.
- Record keeping – documenting all checks, maintenance activities and corrective actions.
A Water Regulations course can support those who need to understand how these control measures sit within wider water hygiene regulations and building services responsibilities.
3. Review the Risk Assessment
A Legionella risk assessment is not a one‑off exercise. It must be reviewed:
- Regularly at intervals appropriate to the risk profile and complexity of the system.
- When circumstances change, such as refurbishment, changes in building use, new plant, altered occupancy patterns or evidence of control issues.
- When there is reason to suspect it is no longer valid. For example, following an incident, audit findings or significant changes in guidance.
Good practice is to set a clear review frequency and to reassess whenever changes could affect risk, rather than waiting for a problem to emerge.
Legionella Prevention Best Practices
Effective Legionella prevention is about combining good system design with consistent management, monitoring and staff competence.
Managing Hot and Cold Water Systems
For most buildings, hot and cold water systems are the main focus. Key points include:
- Water temperatures – keeping stored and circulating hot water at appropriate temperatures, while ensuring cold water stays below recognised thresholds to discourage bacterial growth.
- Circulation – maintaining good flow and circulation, avoiding stagnation in secondary circuits.
- Storage – minimising unnecessary storage and ensuring tanks are clean, insulated and accessible for inspection.
- Dead legs – removing redundant pipework and fittings that can harbour stagnant water.
These steps help create conditions that are hostile to Legionella growth.
Monitoring and Maintenance
Prevention only works if controls are monitored and maintained over time. Duty holders should ensure:
- Regular inspections of tanks, plant rooms, distribution systems and outlets.
- Cleaning and maintenance based on manufacturer guidance and water hygiene best practice.
- Water sampling (where appropriate) targeted microbiological testing if risk, guidance or assessment findings indicate it is needed.
- Consistent documentation recording of checks, inspections, test results and remedial actions.
Clear records help demonstrate Legionella compliance and provide evidence for audits or investigations.
Training Responsible Persons
Legionella prevention is not just about hardware and temperatures. It also depends on people. Staff involved in water system management must be competent and understand the risks and controls they are working with.
Duty holders and responsible persons need clear knowledge of their legal obligations and day‑to‑day duties so they can apply Legionella control measures correctly and consistently. They also need good compliance awareness and a commitment to ongoing learning, keeping up to date with changes in guidance and industry practice.
Why Water Hygiene Training Supports Compliance
Appropriate Legionella and water hygiene training supports this by building confidence, improving practical understanding of systems and regulations, and helping organisations demonstrate that those managing water safety are suitably informed and competent.It gives duty holders and responsible persons the confidence and knowledge they need to manage water systems safely.
Understanding Your Legal Responsibilities
Good training helps delegates:
- Grasp the legal framework behind Legionella duties, including ACOP L8, HSG274, COSHH and related regulations.
- Build risk awareness to understand where Legionella is likely to be a problem and how exposure can occur.
- Apply practical knowledge to real sites, rather than treating compliance as a purely theoretical exercise.
Building Confidence in Water Safety Management
Training also supports day‑to‑day water safety management:
- Identifying hazards in hot and cold water systems, cooling towers and other risk systems.
- Applying appropriate control measures, from temperature regimes to flushing and maintenance.
- Supporting workplace safety by embedding Legionella control into broader health and safety policies.
For those responsible for hot water installations, Logic4training’s hot water systems and safety (unvented hot water) course can be particularly valuable.
Keeping Knowledge Up to Date
Regulations and industry guidance evolve over time. Ongoing training and refresher courses:
- Help duty holders track updates to guidance, such as revisions to HSG274 or sector‑specific recommendations.
- Reinforce best practice and lessons learned from incidents and case studies.
- Ensure that responsible persons do not rely on outdated assumptions about risk and control.
Are You Meeting Your Legionella Responsibilities?
Use the decision table below to sense‑check your position.
Conclusion: Managing Legionella with Confidence
Legionella risk assessments are a fundamental part of managing water safety and meeting legal responsibilities. Understanding who the duty holder is, following ACOP L8 and HSG274 guidance, and maintaining effective control measures all help protect building occupants and demonstrate Legionella compliance.
Whether you are a landlord, employer or facilities manager, investing in your knowledge of Legionella prevention and water hygiene is key. Competent duty holders and responsible persons are better able to design, implement and oversee proportionate control schemes, and to keep assessments current as buildings and systems evolve.
Develop the Knowledge Needed to Manage Legionella Risks with Confidence
View our Legionella courses to build your competence in Legionella risk assessment, water safety management and compliance.
Operatives legionella training
FAQs
Is a Legionella risk assessment a legal requirement?
Yes. If you control premises where people could be exposed to Legionella from water systems, UK health and safety law requires you to identify and assess that risk, and to implement appropriate controls. ACOP L8 and HSG274 set out how to meet these duties in practice.
What are the L8 regulations?
“L8 regulations” refers to ACOP L8: the HSE Approved Code of Practice for controlling Legionella bacteria in water systems. It explains how duty holders should carry out risk assessments, appoint competent people, implement written schemes of control, monitor systems and keep records to comply with existing health and safety law.
What does a Legionella risk assessment involve?
A Legionella risk assessment involves inspecting your water systems, identifying hazards and potential sources of bacterial growth, assessing who could be exposed, recording findings in a clear report and recommending control measures such as temperature regimes, flushing, cleaning and monitoring.
How often should a Legionella risk assessment be reviewed?
Risk assessments should be reviewed regularly and whenever circumstances change in ways that could affect risk. ACOP L8 states that the assessment must be revisited when there is reason to suspect it is no longer valid, for example after system modifications, changes in building use, occupancy patterns or evidence of control problems.
Do landlords need a Legionella risk assessment?
Yes. Landlords who rent out properties have a legal duty to protect their tenants’ health and safety, which includes assessing and controlling the risk from Legionella in domestic water systems. HSE guidance makes clear that this duty applies, though in many low‑risk domestic properties a simple, proportionate assessment is sufficient.
Your latest offers & alerts