What qualifications should a legionella risk assessor have?

In the UK, a legionella risk assessor should be able to demonstrate relevant formal training, practical experience in water-system management, and the technical competence to assess the particular systems within scope. There is no single universal licence that qualifies a person to assess every type of water installation. Competence depends on the assessor’s knowledge, experience, training and ability to apply that knowledge accurately to the site being reviewed.

Relevant formal training

The assessor should have completed a recognised course specifically covering legionella risk assessment and water hygiene. Suitable training normally includes the sources and transmission of legionella, factors that allow bacteria to multiply, water-system design and operation, control measures, monitoring requirements, sampling considerations and the production of a risk assessment report.

General legionella awareness training is not normally enough for this role. Awareness courses explain the hazard and individual responsibilities, but they do not usually develop the deeper skills needed to survey a complex system, identify foreseeable failure points, judge the significance of findings or specify proportionate remedial action. The course content, assessment method and level of study should therefore be checked rather than relying on the course title alone.

Practical experience with relevant water systems

Training should be supported by experience of inspecting and understanding the types of installation being assessed. This may include hot and cold water systems, storage tanks, calorifiers, secondary return loops, showers, thermostatic mixing valves, infrequently used outlets and associated distribution pipework. Where relevant, the assessor should also understand more specialised systems such as cooling towers, evaporative equipment, spa pools or healthcare water installations.

The necessary experience depends on the site. An assessor who is competent to review a straightforward office water system may not have the expertise required for a hospital, care setting, manufacturing facility, hotel, leisure site or premises with process water. The assessor should be able to explain how their previous work relates to the system’s design, use, occupants and level of risk.

Ability to carry out a complete assessment

A qualified assessor must do more than identify the presence of tanks, outlets or temperature controls. They should be able to:

• review available schematic drawings, asset information, maintenance records and monitoring results;
• trace the system in practice and compare it with available documentation;
• identify dead legs, redundant pipework, low-use outlets, stagnation points, poor insulation, inappropriate temperatures and other conditions that may increase risk;
• consider how the system is operated, maintained, altered and used by occupants;
• recognise gaps in ownership, control responsibilities and monitoring arrangements;
• evaluate the significance of each finding rather than presenting an unprioritised list of defects; and
• produce practical recommendations that match the level of risk and can be assigned to responsible persons.

This requires sound judgement. An assessment should distinguish between an immediate control concern, a deficiency requiring planned correction and a recommendation for improved management. It should also explain the evidence supporting each conclusion, so that the dutyholder can understand what needs to happen and why.

Knowledge of technical controls

The assessor should understand how temperature control, system design, water turnover, cleaning, disinfection, flushing and maintenance affect legionella risk. They should know the limitations of each control. For example, recording a temperature does not by itself demonstrate that all parts of a system are adequately controlled, while periodic flushing may not resolve a fundamental design problem or persistent stagnation.

They should also recognise when a recommendation requires input from another competent specialist, such as a water-treatment professional, mechanical services engineer, electrical contractor or building designer. A responsible assessor does not make unsupported recommendations outside their expertise.

Sampling and laboratory awareness

Where water samples are appropriate, the assessor should understand when sampling may provide useful evidence, how sampling points should be selected, how samples can be affected by collection and transport, and how results should be interpreted alongside the wider assessment. A laboratory result is not a substitute for examining the system, and a negative result does not prove that risk is permanently absent.

The assessor does not necessarily need to be a laboratory analyst, but they should understand the limits of test results and be able to distinguish between an assessment, sample collection and laboratory examination. Any laboratory arrangements, sample methods and interpretation should be transparent to the dutyholder.

Understanding of management responsibilities

Competence includes understanding how the assessment fits into the organisation’s wider water-safety arrangements. The assessor should be able to identify the dutyholder or responsible person, clarify who carries out monitoring and maintenance, define escalation routes and indicate when the assessment should be reviewed.

The report should be sufficiently clear for managers, maintenance teams and contractors to use. It should normally record the systems inspected, areas not accessed, information relied upon, significant findings, recommended controls and any limitations that could affect the conclusions. A report that is technically detailed but unclear about actions and ownership is of limited practical value.

Current knowledge and continuing development

Qualifications should not be treated as permanent proof of competence. Water systems, industry practice and published requirements change, while an assessor’s knowledge can become outdated if it is not maintained. Evidence of continuing professional development, refresher learning, relevant site work and review of technical updates can help demonstrate that competence remains current.

It is also sensible to ask whether the assessor works within a documented quality process. Peer review, report checking, standard inspection methods, controlled templates and clear arrangements for handling technical queries can reduce inconsistency. These measures support competence but do not replace the individual’s own knowledge and experience.

What a client should check before appointment

• the exact title, provider and scope of the assessor’s relevant training;
• the types of premises and water systems they have assessed;
• their experience with systems of similar complexity and risk;
• how they maintain and evidence continuing competence;
• whether the assessment will be completed personally or partly delegated;
• what the inspection and report will include; and
• whether any proposed sampling, specialist inspection or remedial advice is within their competence.

For higher-risk or technically complex premises, the appointment should be based on demonstrated capability rather than the cheapest quotation or a generic certificate. A competent assessor should be willing to explain their qualifications, experience, scope and limitations before starting work. The dutyholder remains responsible for making sure the person appointed is suitable for the specific assessment, even when an external specialist is used.