What triggers a change to a Legionella risk assessment schedule?
A legionella risk assessment schedule should change when a water system, its use, its occupants or its control measures change in a way that could alter the risk. It should also be revised after a legionella incident, significant monitoring findings, or a review showing that the existing assessment no longer reflects current conditions.
A change to a legionella risk assessment schedule is justified when the information, conditions or controls on which the assessment is based are no longer current. The change may involve bringing the next review forward, adding an interim assessment, revising the scope, or setting a different review interval. It should be based on a documented evaluation rather than an arbitrary calendar change.
Common triggers include:
- Alterations to the water system: New tanks, calorifiers, showers, outlets, pipework, treatment equipment or changes to hot and cold water distribution can create different routes for exposure or new areas where water may stagnate.
- Changes in how the premises are used: A change from office, residential or industrial use to another type of occupation may alter water demand, outlet usage and exposure patterns. Extended vacancy, partial occupation or the reopening of a building after a prolonged closure also warrants a review before normal use resumes.
- Changes to the people using the premises: Facilities used by people who may be more susceptible to serious illness, including healthcare-related or care settings, require the assessment to reflect the relevant vulnerability and exposure arrangements.
- Changes to management or maintenance arrangements: A new responsible person, contractor, operating procedure or water hygiene regime can affect how risks are controlled. The assessment schedule should identify who has authority to act, who receives monitoring results and who escalates a failure.
- Evidence that controls are not working as intended: Unacceptable temperatures, repeated low-use outlets, failed dosing, inadequate flushing, damaged insulation, poor tank condition or recurring corrective actions may indicate that the existing assessment and control plan need to be reconsidered.
- Changes in monitoring results: Trends in temperature records, microbiological test results or inspection findings can reveal a developing risk even where there has been no obvious system alteration. A single result should be interpreted by a competent person, while repeated or significant findings may require an earlier assessment.
- Building, refurbishment or demolition work: Work can leave redundant pipework, introduce dead legs, disturb tanks or change access to plant. The assessment should be reviewed before work, where the work affects the system, and before affected areas return to use where necessary.
- An incident or suspected case: A confirmed or suspected legionella-related illness, an outbreak investigation or a serious water hygiene failure should prompt a review of the relevant assessment and control measures. The revised schedule should record the investigation, actions taken and any further review required.
A schedule should also be changed when a periodic review identifies that the original assessment is incomplete, relies on outdated drawings, does not cover all outlets, or no longer reflects the current responsible persons. This can happen even when routine monitoring has not identified a failure. The assessment is a record of actual conditions, not simply a document that remains valid because its nominal review date has not arrived.
Not every maintenance activity requires a completely new risk assessment. Replacing a like-for-like component may be managed through the existing control procedures if it does not change the risk profile. However, the decision should be recorded, including what was checked and why the existing assessment remains suitable. If the work changes temperatures, flow, storage, outlet use, access or exposure, the assessment schedule should be reconsidered.
When a trigger is identified, the review process should establish:
- What has changed and when it changed.
- Which parts of the water system, building or user population are affected.
- Whether the existing risk assessment still describes the installation accurately.
- Whether additional sampling, inspection, remedial work or interim controls are needed.
- Who is responsible for completing and approving the review.
- When the next review or follow-up check is due.
The amended schedule should link to the updated assessment and retain a clear audit trail. Records should show the reason for the change, the assessment date, the person carrying out the review, relevant findings, actions, completion dates and the date of the next planned review. Where a change affects only one building or part of a larger estate, the schedule should identify that scope rather than treating every site as if the same conditions apply.
For organisations managing several premises, a trigger at one site should not automatically be copied across all sites. A common policy or review cycle may be useful, but each property still needs to be considered against its own system design, use, occupants, monitoring evidence and control arrangements. A competent legionella risk assessment process should therefore allow both planned reviews and event-driven changes to the schedule.
A trigger does not automatically require a completely new legionella risk assessment. The appropriate change to the schedule depends on whether the event affects the water-system hazard, people’s exposure, or the reliability of existing controls.
- No schedule change: the matter has been checked and demonstrably has no effect on risk, such as work that leaves system operation and use unchanged.
- Targeted review: the change is limited to a defined plant area, outlet group or operating process, so the relevant assessment section and follow-up date can be amended.
- Full reassessment: the event changes the system design, exposure profile or control strategy sufficiently that the original assessment can no longer be relied upon as a complete description.
This triage should be made by a competent person and recorded with the reason for the decision. Keeping the rationale is important where the outcome is to retain the existing review date, as it demonstrates that the trigger was considered rather than overlooked.
Discuss your Legionella risk assessment schedule
Discuss your legionella risk assessment schedule with Blue Fish Water Management Ltd to review whether a recent change requires a targeted update or further assessment. Our team can help you identify the appropriate next step and maintain clear, defensible records.