Legionella is a potentially harmful bacterium (Legionella Pneumophila) found in water systems that can cause severe illnesses such as Pontiac Fever and Legionnaires’ Disease. Pontiac Fever is a mild, flu-like illness, whereas Legionnaires’ Disease is a potentially fatal form of Pneumonia. In the UK, a legionella risk assessment is a legal requirement under ACoP L8 and HSG274 (Parts 1, 2 and 3) to protect users of a building and ensure compliance with health and safety regulations.
This guide will outline who needs one, what a comprehensive assessment covers and why it’s essential for risk management and legal compliance.
Who needs a Legionella Risk Assessment?
A Legionella risk assessment is legally required for any premises with a water system capable of creating aerosols, or airborne water droplets, that could be inhaled and infect building users if the bacterium is present. This includes:
- Healthcare facilities – hospitals, clinics and dental practices
- Residential care homes and supported living facilities
- Hotels, hostels and guesthouses
- Educational institutions – schools, nurseries, colleges and universities
- Commercial properties – offices, restaurants and pubs
- Gyms, leisure centres, spas and swimming pools
- Industrial properties with water processes, cooling towers or HVAC systems
- Multi-occupancy properties – social housing and landlord rentals
Under COSHH (Control of Substances Hazardous to Health) and HSE (Health and Safety Executive) guidance, businesses of over 5 employees must assess legionella-related risks, implement control measures and demonstrate ongoing compliance. The frequency of a Legionella risk assessment should reflect the complexity of the system and the level of risk. Best practice is usually around every 2 years, but this frequency depends on the building’s specific water systems and if any changes occur. The current guidance suggests ‘regularly’ and at an ‘ongoing’ frequency to remain compliant.
The complete Legionella Risk Assessment checklist
General inspection
A thorough Legionella risk assessment must begin with a general inspection conducted by a trained and competent assessor. The assessor will:
- Review the current building schematics to identify all hot and cold water systems across the premises.
- Inspect all water system components such as plant rooms, water storage tanks, calorifiers and any aerosol-generating outlets such as showers, spray taps and cooling towers.
- Check maintenance records, previous assessments and any Legionella testing logs.
The assessor will identify any overlooked water systems, such as decorative fountains, spa pools, hosepipes and infrequently used taps that might harbour stagnant water where the bacterium could grow. This Legionella risk assessment is a vital foundation to understanding potential bacterial routes, the complexity of the system and operational patterns of the property.
System condition assessment
After the general inspection, the assessor evaluates the physical condition and the cleanliness of every component of the water system, including:
- Cold water tanks – cleanliness, structural integrity, presence of debris or insects, insulation, secure lids, stored water temperature and any associated non-conformities.
- Hot water tanks – calorifiers, hot water cylinders, operating temperatures and any associated non-conformities.
- Pipework – checks for blind ends, poor insulation or any areas at risk of stagnation like ‘dead legs’ (redundant pipework).
- Outlets – taps, hoses and showerheads need to be checked for scale, sediment or biofilm buildup.
This stage ensures that the system is physically well-maintained, and if any conditions could contribute to a microbial risk. A well-documented water system condition assessment provides the information necessary to prioritise remedial work and maintain the hygiene of the entire system, ensuring it is fit for safe operation and maintenance.
Temperature profiling
One of the most important ways to control Legionella bacteria is to ensure temperatures remain within specific ranges. During a H2O Hygiene Legionella risk assessment, the assessor will carry out temperature profiling to check that representative temperatures are consistent across the system. This involves testing sentinel outlets, typically the first and last taps on each loop or floor, the return temperature on hot water systems and any outlets known to have poor flow or temperature history.
Hot water should reach 50°C within one minute at the tap outlet (non-healthcare – 55°C for healthcare premises), and cold water should be maintained below 20°C within two minutes, as water that remains within these two levels can allow the bacterium to breed and proliferate rapidly. All readings should be documented and cross-referenced with HSE guidance, and any outlets or systems outside these limits must be flagged for investigation with your Water Hygiene provider.
Schematic diagram
A comprehensive Legionella risk assessment must include an accurate, updated schematic diagram of the entire water system. The schematic is like a roadmap of your property’s water system components and also indicates the flow of water, identifies sentinel points and marks any recommended sampling locations for ongoing monitoring. A high-quality schematic should also highlight any vulnerabilities in the system.
The assessor will review and update the schematic diagram during the risk assessment to reflect any changes made since any previous versions. An up-to-date schematic helps to ensure that monitoring, maintenance and disinfection activities are properly registered and tracked, preventing these activities from becoming disorganised or ineffective and increasing Legionella risks.
Control measures review
When undertaking a Legionella risk assessment, a review must be made of your property’s control measures. This should include:
- Flushing of infrequently used outlets
- Cleaning and descaling of showers and taps regularly
- Chemical or thermal disinfection practices
- Record keeping for temperature logs, maintenance schedules and biocide dosing reports
- Staff training
Reviewing the control measures helps to assess how well the Responsible Person is undertaking their duties under COSHH and ACoP L8 regulations, and that all legal obligations and health and safety laws are being adhered to.
Recommendations and action plans
The Legionella risk assessment should result in a detailed report which includes risk ratings for every area of the water system: low, medium or high risk. This will then lead to tailored recommendations to address any non-compliance or hazards. Some of the recommendations and action plans could include:
- Improving temperatures
- Removing redundant pipework (dead legs)
- Improving insulation
- Increasing flushing schedules
- Chemical treatments
It will outline a clear plan of action with timelines and priority levels for getting the recommendations and any remedial works implemented. A clear, prioritised plan helps decision-makers make smart choices about budget spending and ensures ongoing improvement in water safety management. Most importantly, it shows due diligence and supports your legal defence in the case of an investigation.
Legionella management advice
Your assessor will offer guidance on how to maintain compliance after the risk assessment, including clarification of the Responsible Person’s duties and responsibilities. This includes:
- Regular water temperature monitoring
- Frequent flushes of used and unused outlets like taps and showers
- Staff training in Legionella awareness
- Cleans and descales of water outlets
- Regular Legionella risk assessment reviews, with up-to-date records
Following these steps helps you to embed water safety into your operations and forms a foundation for compliance and health protection.
Why does a Legionella Risk Assessment matter?
A Legionella risk assessment offers more than legal and regulatory compliance; it also acts as a protective measure against illness outbreaks and potential legal exposure. Failure to comply with ACoP L8 or HSG274 can result in large fines, enforcement action from the HSE and potential business closure. From a health standpoint, detailed risk assessments significantly reduce Legionnaires’ disease cases, protecting vulnerable building occupants and organisations’ reputations. Rushing, or not conducting a Legionella risk assessment thoroughly enough, can mean missing critical hazards and can lead to sickness outbreaks, which may have massive legal, financial and reputational consequences.
Need a Legionella assessment? Book today!
Don’t wait until your system fails, your building’s occupants get sick or you face regulatory or legal issues. Proactively facing your Legionella risk assessment and legal obligations is essential. Secure your compliance and the safety of your building and occupants today.
H2O Hygiene are experts at providing comprehensive Legionella risk assessments, bespoke action plans and ongoing compliance support across the UK. With years of expertise behind us, you can be sure that our highly qualified specialists can guide you through every step. Call us on 01922 666108, email us at [email protected] or book your assessment with our contact form.
Ensure your site is safe, compliant and confidently managed with H2O Hygiene.
