Legionella Risk Assessment — Water Safety Compliance Across the UK

Yes. Under the Health and Safety at Work Act 1974, employers and those responsible for premises have a legal duty to manage the risk of Legionella bacteria in water systems. The HSE's Approved Code of Practice L8, "Legionnaires' Disease: The Control of Legionella Bacteria in Water Systems", sets out specific requirements for managing this risk, including the need for a documented risk assessment carried out by a competent person. L8 has special legal status: while it is not legislation itself, failure to follow it can be used as evidence of non-compliance in enforcement proceedings. The duty applies to employers, self-employed people and those in control of premises, including commercial landlords, facilities managers and managing agents. Failure to comply can result in HSE enforcement action, including improvement notices, fines and, in the event of a Legionnaires' disease outbreak, prosecution. A documented Legionella risk assessment is the starting point for all Legionella control measures and the foundation of any compliant water safety programme. 

 Anyone responsible for premises with a water system that could pose a Legionella risk needs a risk assessment. This includes commercial and residential landlords — particularly those with HMOs or communal hot water systems — hotels and guest houses, care homes and healthcare facilities, leisure centres and swimming pools, industrial sites with cooling towers or evaporative condensers, office buildings and multi-tenancy properties, dental practices and food production or hospitality businesses. The duty is not limited to large organisations. Small businesses and individual landlords with shared water systems can fall within scope depending on the type of water system present. The relevant test is whether you have control of the premises or the water system — not whether you own the building. If you are unsure whether a Legionella risk assessment is required for your premises, York Green can advise based on the specific water systems present and the nature of the building's use and occupancy. 

A Legionella risk assessment covers any water system that could create conditions for bacterial growth and dispersal. The most common systems assessed include hot and cold water services, hot water cylinders, calorifiers, cold water storage tanks and distribution pipework, cooling towers and evaporative condensers, which pose the highest risk of large-scale Legionnaires' disease outbreaks, spa pools and whirlpool baths, decorative fountains and water features, humidifiers, dental water lines, and any other system that produces water droplets or aerosols that could be inhaled by building occupants. The assessment focuses on water temperature, stagnation risk, the presence of nutrients that support bacterial growth, such as scale, rust, sludge and biofilm, water treatment regimes in place, and the proximity of the system to people who may be at increased risk of infection. Not all premises will have all system types, the assessment covers only the systems present. 

 HSE Approved Code of Practice L8 does not specify a fixed review interval but requires the risk assessment to be kept current and reviewed whenever there is reason to believe it may no longer be valid. A review is required when the water system is modified or extended, when the use or occupancy of the building changes significantly, when control measures are found to be inadequate, following a confirmed case of Legionnaires' disease or a positive Legionella detection in the system, or following a period of building closure or system shutdown. As good practice, most assessors and many property insurers recommend reviewing the risk assessment at least every two years for most premises. Higher-risk systems such as cooling towers should be reviewed more frequently as part of an ongoing monitoring and maintenance programme. Any significant change to the water system, including new plant, altered pipework or changes to usage patterns, should trigger an immediate review regardless of when the last assessment was carried out. 

 L8 requires the assessment to be carried out by a competent person, defined as someone with the necessary knowledge, experience and skills to identify and assess Legionella risks in the type of water system being assessed. In practice, this means the assessor must understand the relevant regulations and HSE guidance including L8 and HSG274, have knowledge of water system design and operation, understand the conditions that promote Legionella growth, and be able to identify appropriate control measures and monitoring requirements. Competence cannot be demonstrated by qualification alone — the assessor must have practical familiarity with the specific type of water system being assessed. For high-risk or complex systems such as cooling towers, specialist expertise is particularly important and assessors with specific cooling tower experience should be used. York Green's assessors hold professional qualifications in health and safety and have specific experience in water hygiene risk assessment across a range of commercial and industrial premises types. 

 The Approved Code of Practice L8 - "Legionnaires' Disease: The Control of Legionella Bacteria in Water Systems", is the HSE's definitive guidance on managing Legionella risks in water systems. It has a special legal status: while it is not legislation in itself, following L8 is the recognised standard of compliance for Legionella control in the UK. Failure to follow the guidance in L8 can be used as evidence of non-compliance in enforcement proceedings brought by the HSE. L8 sets out the duty to identify and assess the risk from Legionella bacteria, the need for a written scheme of control, the requirement to implement and manage control measures, and the obligation to keep adequate records. It is supported by a series of technical guidance documents, HSG274 Parts 1, 2 and 3, which provide detailed technical guidance for specific water system types including evaporative cooling systems, hot and cold water systems and other risk systems. Any Legionella risk assessment carried out for a UK business should be conducted in accordance with L8. 

 Following a Legionella risk assessment, York Green produces a written report identifying the water systems assessed, the risk level associated with each system, hazards identified, such as dead legs, temperature excursions, inadequate treatment or lack of monitoring, and a prioritised action plan. Where a significant risk is identified, L8 also requires a written scheme of control, commonly referred to as a water risk management plan or control scheme, setting out the specific control measures, monitoring requirements, frequencies, responsible persons and review arrangements. For lower-risk premises where existing controls are adequate, documentation of the assessment and confirmation of those controls may be sufficient without a full control scheme. York Green's report clearly indicates what level of control documentation is required based on the risks identified, and provides guidance on implementing the necessary measures. Where ongoing monitoring, such as temperature checks, chlorination or water sampling, is required, the control scheme sets out exactly what needs to be done and how often. 

 A Legionella risk assessment is a systematic, documented evaluation of whether water systems on your premises could create conditions that allow Legionella bacteria to grow and spread. It identifies hazards, evaluates risks and recommends control measures. Legionella testing — also called water sampling or microbiological monitoring — involves taking water samples from the system and submitting them to an accredited laboratory for analysis to detect whether Legionella bacteria are currently present. The two are complementary but distinct activities. An assessment tells you whether the conditions for bacterial growth exist; testing tells you whether bacteria are present at a given point in time. L8 requires a risk assessment as the foundation of any Legionella control programme. Routine testing is a monitoring activity that may be required as part of your control scheme — particularly for cooling towers and higher-risk systems — but it does not replace the need for a risk assessment. York Green carries out risk assessments in accordance with L8. Water sampling and laboratory analysis is carried out by accredited laboratories and can be arranged separately as part of an ongoing monitoring programme.