Can an existing Legionnaires risk assessment be used?

Yes, an existing Legionnaires’ risk assessment may be used, but only if it is a reliable assessment of the premises and water systems as they currently operate. There is no universal expiry period that makes every assessment invalid on a particular date. Its suitability depends on its quality, scope, supporting evidence and whether conditions have remained materially unchanged.

A responsible person should be able to demonstrate that the assessment:

• covers every relevant water system, including hot and cold water services, stored water, showers, spa pools, cooling systems or other higher-risk equipment where present;
• identifies sources and routes of exposure to water droplets or aerosols;
• considers people who may be exposed, including workers, visitors, residents, patients or other vulnerable groups;
• sets out the control measures required and who is responsible for implementing them;
• is based on an inspection of the actual installation rather than plans or assumptions alone; and
• has enough detail to support ongoing monitoring, maintenance and review.

The competence of the person who prepared the assessment is also important. Competence involves suitable knowledge, training and practical experience of legionella risks and the types of water systems being assessed. A document that is generic, incomplete or produced without appropriate access to the installation may not provide a sufficient basis for managing risk, even if it is relatively recent.

Check the assessment against the current premises before relying on it. Compare its descriptions and schematic information with the installation, confirm that outlets and equipment are included, and verify that stated temperatures, control measures and responsibilities remain accurate. Records of monitoring, cleaning, maintenance, sampling and remedial work can help establish whether the arrangements described in the assessment are operating in practice.

A review is normally needed when there has been a change that could affect legionella risk. Examples include:

• alterations, extensions, refurbishment or changes to the water system;
• changes in building use, occupancy, population or patterns of water demand;
• periods of reduced use, closure, vacancy or recommissioning;
• changes to the responsible person, maintenance arrangements or contractors;
• evidence of stagnation, poor temperature control, unusual water conditions or ineffective control measures;
• positive or concerning sampling results, illness concerns or other indications of possible exposure; and
• findings from inspections, audits, incidents or remedial works that reveal previously unrecognised risks.

A review does not always require a completely new assessment. If the existing document remains fundamentally sound, a competent reviewer can confirm what is still accurate, record the changes, update the risk conclusions and revise the control scheme. A new or substantially revised assessment is more appropriate where the original scope was inadequate, the system has been significantly altered, the building’s use has changed considerably, or the available information cannot be verified.

It is important to distinguish an assessment from the control scheme that follows it. Using an existing assessment does not remove the need for suitable monitoring, inspection, maintenance, cleaning and records. The responsible person must continue to manage the identified risks and act on findings rather than treating the assessment as a one-off compliance document.

For a practical review, retain the original assessment, note its date and scope, document any changes since it was prepared, and record the reason for deciding that it remains suitable or requires revision. Blue Fish Water Management Ltd can support this process through legionella risk assessments, compliance audits, water testing, system monitoring and remedial advice, helping organisations establish whether existing documentation still reflects their current arrangements.