When should a commercial legionella risk assessment be completed?
A commercial legionella risk assessment should remain current for the life of the premises and its water systems. There is no single review interval that is suitable for every organisation: the appropriate timing depends on the complexity of the system, the people who may be exposed, the condition of the installation and the effectiveness of existing control measures. The assessment should therefore be reviewed at planned intervals set by the responsible person, as well as whenever circumstances could alter the level of risk.
Under the Health and Safety at Work etc. Act and the Control of Substances Hazardous to Health Regulations, employers and people in control of non-domestic premises must assess and control risks from legionella where exposure could occur. The assessment should be suitable and sufficient, proportionate to the premises, and based on the actual water systems rather than a generic template.
Factors that influence when a review is needed include:
- the type, size and complexity of hot and cold water systems;
- dead legs, storage tanks, calorifiers, showers, spa facilities, cooling systems or other assets that may create conditions for bacterial growth;
- the age, condition and history of the installation;
- whether occupants, residents, patients or visitors may be particularly susceptible to legionnaires’ disease;
- the reliability of temperature control, disinfection, flushing and other preventive measures; and
- the quality of records showing that control tasks have been completed and acted upon.
A planned review is particularly important where the assessment is old, lacks supporting evidence or no longer reflects the people using the building. It should also consider changes in occupancy or use, periods of low occupancy, alterations to water demand and parts of the system that are rarely used. These conditions can affect stagnation, temperatures and the likelihood of exposure even where the physical installation has not changed.
The review should be carried out by someone with sufficient knowledge, training and experience to understand legionella risks and the systems being assessed. That may be a suitably competent employee or an external specialist, depending on the complexity of the premises and the organisation’s own expertise. The responsible person remains accountable for ensuring that the assessment is completed, acted upon and kept available for those carrying out control duties.
A proper reassessment normally involves examining schematic information, inspecting accessible plant and outlets, considering maintenance and monitoring records, checking current control measures and speaking with relevant site personnel. Where the available information indicates a potential problem, additional investigation or water testing may be appropriate. Testing does not replace the risk assessment; it provides evidence that may help determine whether controls are working or whether further action is required.
If the assessment identifies an unacceptable risk, interim precautions may be needed while remedial work is arranged. Depending on the circumstances, these could include restricting access to an affected outlet, increasing flushing, correcting temperature problems, removing redundant pipework or improving cleaning and disinfection arrangements. Any decision should be documented, allocated to a responsible person and followed through to completion.
Records should show the date of the assessment, its scope, the systems and outlets considered, significant findings, control measures, responsibilities, recommended actions and the date or circumstances for the next review. Keeping this information with monitoring and maintenance records helps demonstrate that legionella control is being managed as an ongoing process rather than treated as a one-off document.
Blue Fish Water Management provides commercial legionella risk assessments, water testing, compliance audits and related control advice for organisations across the UK. Its approach can help businesses establish when a review is justified, identify gaps in their existing arrangements and translate the findings into practical control measures.
A commercial legionella risk assessment should be reconsidered before a building or water system is brought back into use after an extended closure. Periods without normal water demand can allow stagnation, temperature changes and loss of confidence in routine control measures, so the original assessment may not accurately represent conditions at reopening.
Before normal occupancy resumes, the responsible person should establish what parts of the system have remained in use, identify outlets or equipment that have been isolated, and check whether flushing, cleaning, disinfection or other recommissioning work is needed. The assessment should then be updated where the closure has altered the hazards, the control arrangements or the people likely to be exposed.
This does not mean that every short interruption automatically requires a completely new assessment. The decision should be based on the duration and nature of the closure, the complexity of the installation, the condition of the water system and the evidence available from inspection and maintenance records. Where that evidence is incomplete, a reassessment before reopening provides a more reliable basis for deciding whether the premises is ready for normal use.
Discuss your commercial legionella risk assessment
If you are unsure whether your commercial legionella risk assessment is still suitable, discuss your premises and review requirements with Blue Fish Water Management. Their team can advise on the appropriate next step and any supporting evidence needed.