What evidence should a sector-specific Legionella Risk Assessment provide to regulators?

For regulators, a sector-specific Legionella Risk Assessment should provide an auditable chain from the site’s actual water systems and activities to the decisions made to control risk. It should show not only what was inspected, but why particular hazards were considered relevant, how the findings were prioritised and how the duty holder can demonstrate that controls remain effective.

Evidence should be specific to the site and sector. A generic assessment or copied description is unlikely to demonstrate adequate control. The document should identify the types of water systems present, their locations, users, operating conditions and foreseeable exposure routes. It should also explain any sector-specific factors that alter the risk, such as vulnerable occupants, patient or resident care, public access, aerosol-generating processes, bathing facilities, industrial plant or periods of low occupancy.

A regulator should be able to distinguish between:

• information verified during the assessment;
• information supplied by the duty holder;
• assumptions made because records or access were limited; and
• matters requiring further investigation.

Photographs, system schematics, asset registers, inspection notes and clear cross-references can help demonstrate how conclusions were reached. These records should identify the relevant plant or outlet rather than relying on general descriptions such as “hot water system” or “low-use outlets”. Where a system could not be inspected, the limitation and its effect on the assessment should be recorded.

The reasoning behind the risk rating is important. Regulators may examine whether the assessment considered factors such as water temperature, stagnation, system complexity, storage arrangements, recirculation, dead legs, scale or corrosion, access for maintenance, potential aerosol production and the susceptibility of exposed people. The assessment should explain how these factors combine at the particular premises, rather than simply assigning a high, medium or low rating without justification.

Where controls differ between parts of a site, the evidence should show that distinction. For example, a healthcare setting may need separate consideration of clinical areas, staff facilities and plant rooms, while a manufacturing site may need separate treatment of welfare outlets, process-related systems and cooling equipment. The relevant issue is whether the assessment reflects the way the premises are actually occupied and operated.

Evidence should also demonstrate management ownership. A regulator will generally need to identify who has responsibility for the water systems, who is authorised to make decisions and how information is passed between estates, facilities, operations and specialist contractors. A clear responsibility structure should cover routine control, escalation of abnormal results, approval of remedial work and review of the assessment when circumstances change.

The assessment should link significant findings to a controlled action process. Each action should have a clear description, priority, responsible person and target for completion, together with a record of the eventual outcome. If an action remains open, the evidence should explain the interim control and why the remaining risk is being managed. Closing an action should mean more than marking it complete: the file should show what was changed and, where relevant, how the change was checked.

Monitoring evidence needs to be interpretable, not merely present. Records should identify the outlet, asset or system examined, the date, the result, the person undertaking the check and any follow-up required. Trends, repeated failures and unusual results should be visible. A regulator may question records that contain unexplained gaps, identical readings across multiple outlets, inconsistent dates or results that do not match the stated sampling plan.

Where water testing has been undertaken, the evidence should connect the result to the sample location, collection circumstances and laboratory report. It should make clear what prompted the test, how the result was assessed and what action followed. A test result is not, by itself, proof that the system is adequately controlled; its regulatory value depends on the surrounding assessment, interpretation and response.

Records should show that controls operate in practice. Useful supporting evidence can include:

• temperature or other operational check sheets;
• flushing records for outlets subject to infrequent use;
• cleaning and disinfection documentation;
• maintenance and defect reports;
• records of remedial alterations or system changes;
• calibration or verification information for monitoring equipment; and
• meeting, review or escalation records where significant issues were identified.

Documents should be dated and attributable to a named person or defined role. Electronic records should retain enough information to show when an entry was created or amended where that matters to the audit trail. Alterations, late entries and corrections should be transparent rather than obscuring the original information.

Competence evidence should support the tasks being performed. This does not mean retaining certificates without context. The records should help show that people carrying out inspections, monitoring, sampling, cleaning, maintenance or assessment had suitable knowledge and instruction for their responsibilities. Where work is contracted out, the duty holder should retain evidence of the contractor’s scope, competence and reporting, while still demonstrating how the work was reviewed and acted upon internally.

The evidence should also show how changes trigger reassessment. Examples include alterations to hot and cold water services, changes in occupancy, refurbishment, acquisition of new plant, extended periods of disuse, repeated monitoring failures or changes affecting vulnerable people. A dated review record should explain whether the existing assessment remains valid, requires amendment or must be replaced.

A regulator should be able to follow the evidence without relying on verbal explanation. A well-organised file normally includes the current assessment, supporting drawings or asset information, relevant inspection and test records, action tracking, competence information and review history. Superseded documents should be controlled so that staff do not rely on an obsolete assessment or outdated operating instruction.

Finally, the evidence should be proportionate but defensible. It does not need to contain irrelevant paperwork or duplicate every operational record. It does need to contain enough reliable, current and traceable information for a regulator to test the duty holder’s decisions, confirm that significant risks were addressed and understand how unresolved issues are being managed. Where evidence is missing, the responsible organisation should identify the gap, assess its significance and record the steps taken to obtain or recreate the necessary information.