What information is needed before a commercial legionella risk assessment?

Before a commercial legionella risk assessment, the assessor needs enough reliable information to define the assessment boundary, understand how the water systems operate, and identify any factors that could affect exposure or control. A well-prepared site pack should therefore cover the premises, system design, management responsibilities, operational restrictions and any changes that may not be obvious during a visit.

Confirm the scope of the assessment

State which buildings, floors, plant areas and external installations are included. This is particularly important where a site has several occupiers, separate leases, shared plant or water services managed by different parties. Explain where responsibility begins and ends for landlords, tenants, facilities teams, cleaning contractors and maintenance providers. If any areas or systems are excluded, record the reason and identify who is responsible for assessing them.

It is also useful to identify whether the assessment covers only domestic hot and cold water systems or whether other water-related systems are present. Examples can include evaporative cooling equipment, spa pools, swimming pools, irrigation systems, vehicle wash systems, humidifiers and specialist process equipment. These may require different control arrangements and technical knowledge.

Provide current technical information

Available design information should show how water enters, is stored, heated, distributed and returned around the premises. The assessor may need details such as:

• the incoming mains arrangement and any private water supply;
• storage cisterns, calorifiers, instantaneous heaters and secondary circulation;
• temperature control devices, blending valves, expansion vessels and pumps;
• showers, spray taps, hoses, flexible connections and other aerosol-producing outlets;
• infrequently used branches, capped connections, bypasses or sections that may retain stagnant water;
• water treatment equipment, dosing arrangements and filtration; and
• temporary, redundant or recently modified pipework.

Where technical records are incomplete, say so rather than treating an old drawing as accurate. The assessor can then verify the arrangement on site and distinguish confirmed information from assumptions. Details of recent alterations, refurbishments, changes of use or plant replacement are especially relevant because they may have changed water flow, temperatures or outlet use.

Explain how the premises operates

The assessor should understand patterns that affect water demand. Provide information about areas that are occupied seasonally, shut down periodically, used only for events or visits, or subject to fluctuating demand. Note any planned closures, decanting arrangements or changes to occupancy that could alter the way outlets and plant are used.

Include the operating arrangements for outlets that are difficult to access or rarely used. If outlets are routinely isolated, flushed, drained or brought back into service under a particular procedure, describe that procedure and identify who carries it out. This helps the assessor compare the documented arrangements with what happens in practice.

Set out site access and safety requirements

Practical access information can determine what the assessor is able to inspect. Provide details of security procedures, permits, inductions, escort requirements, restricted rooms, roof access, plant-room access and any areas requiring specialist equipment. Identify isolation points and explain whether water systems can be safely accessed, sampled or temporarily taken out of service.

Relevant site safety information may include asbestos records, confined-space arrangements, work-at-height controls, electrical hazards, chemical storage, contamination risks and safeguarding restrictions. This information does not replace the assessment itself, but it allows the inspection to be planned without overlooking areas that require additional controls or permission.

Clarify management and contractor interfaces

Give the assessor a clear description of who carries out each control task and who checks that it has been completed. This should include routine outlet use, temperature checks, flushing, cleaning, disinfection, sampling, maintenance and remedial work. Where several organisations share these tasks, document the handover points and the method used to report defects.

Copies of relevant service specifications and contractor instructions can help establish whether work is being carried out to the intended standard. Details of planned maintenance, restricted access arrangements and procurement requirements may also affect the practicality of recommended controls.

Identify limitations before the visit

Tell the assessor about inaccessible plant, locked areas, unavailable records, isolated systems and any equipment that cannot be operated during the inspection. Also disclose known problems such as damaged insulation, failed temperature controls, poor drainage, intermittent hot-water circulation or outlets that cannot be used normally. Early disclosure allows the assessment to record limitations accurately and avoids presenting incomplete observations as a full picture of the site.

Finally, nominate a person who can answer technical and operational questions during the visit and arrange access to the relevant areas. The assessment remains the assessor’s independent evaluation, but accurate pre-assessment information makes it more likely that the report reflects the actual system rather than only the parts that are easiest to see.