As a facilities manager, ensuring the safety of your building’s water systems is a critical responsibility. One of the biggest risks? Legionella bacteria, which thrive in water systems and can cause Legionnaires’ disease—a potentially fatal form of pneumonia.
To stay compliant and protect building occupants, you need to conduct regular Legionella risk assessments. But how often should these be carried out? This guide breaks down best practices, legal requirements, and key triggers for reviewing your Legionella risk assessment.
How Often Should You Conduct a Legionella Risk Assessment?
The Legal Requirements
There’s no fixed timeframe in UK law that dictates exactly how often you must carry out a Legionella risk assessment. However, under the Health and Safety at Work Act 1974 and ACoP L8 (Approved Code of Practice), facilities managers are legally required to:
✔ Identify & assess risks of Legionella in water systems
✔ Implement control measures to minimise risk
Best Practice: The HSE (Health and Safety Executive) recommends reviewing your Legionella risk assessment at least every two years, or sooner if circumstances change. (hse.gov.uk)
Key Triggers for a New Risk Assessment
Even if your last assessment was recent, you should review and update it immediately if:
The water system changes – New pipework, storage tanks, or equipment modifications can alter risk levels.
The building usage changes – If occupancy increases, decreases, or if the site is used differently (e.g., switching from an office to a healthcare facility).
Monitoring shows issues – If water temperatures, bacteria counts, or biofilm build-up suggest a higher Legionella risk.
An outbreak or reported illness occurs – Even one suspected case of Legionnaires’ disease linked to your building requires immediate investigation.
New compliance regulations or guidance emerge – Industry best practices and HSE recommendations are updated periodically.
Legionella Risk Assessment Best Practices
1. Regular Monitoring & Maintenance
An assessment alone isn’t enough—you need ongoing checks to stay ahead of risks.
Temperature Monitoring – Ensure hot water is above 50°C and cold water below 20°C to prevent Legionella growth.
Tank & Pipework Inspections – Check for rust, biofilm, and sediment build-up that can provide bacteria with nutrients.
Flush Unused Outlets – Stagnant water is a Legionella hotspot. Run infrequently used taps and showers at least weekly.
Regular Water Testing – Periodic sampling helps detect bacterial growth before it becomes a serious issue.
Did you know? Stagnation in unused pipes can turn low-risk systems into high-risk systems in a matter of weeks!
2. Ensure Compliance with ACoP L8 & HSG274
The ACoP L8 Code of Practice and HSG274 guidelines outline water hygiene requirements to keep systems safe. Ensure your facility:
✔ Has a Legionella control plan in place
✔ Uses competent professionals for risk assessments and water treatment
✔ Keeps detailed records of all maintenance, testing, and assessments
3. Staff Training & Awareness
Educate staff and contractors on water hygiene risks
Label non-drinking water sources to prevent cross-contamination
Assign a responsible person to oversee Legionella control measures
Example: One of our manufacturing clients had untrained staff flushing water systems incorrectly, leading to stagnant areas where Legionella could thrive. After training their team and setting up a scheduled maintenance plan, we helped them maintain compliance effortlessly.
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