Legionnaires Assessment

Managing the risk associated with Legionella requires a clear understanding of how a property’s water system operates. Factors such as water storage, temperature control, stagnation, system condition and dead legs can all influence the potential for bacterial growth. We examine the relevant water system and identify conditions that may require attention, providing practical recommendations based on our findings.

Our approach is straightforward and evidence-led: understand the system, identify potential areas of concern and explain what should be addressed. Where additional work is appropriate, we can also support customers with services such as water tank cleaning, chlorination, pipework disinfection and water testing.

Legionella risk management is particularly important in larger, shared or managed water systems where water can be stored, circulated or left unused for periods of time. Understanding the system and identifying potential risk factors is an important part of effective water hygiene management.

An assessment is relevant to almost every commercial or managed building and to any rented home with a hot and cold water system, whatever the size of that system. Employers, landlords letting domestic property, and anyone in control of premises used in connection with a business should have one in place.

Growth is most likely where water sits rather than moves, where temperature control drifts, and where sediment, scale or biofilm give bacteria somewhere to establish. Stored water, rarely used outlets, oversized or poorly insulated tanks, dead legs left after refurbishment, and showers or spray taps all feature regularly in assessment findings. London stock includes many such systems, from loft cisterns above single flats to roof-level plant rooms serving whole blocks.

The assessment identifies whether those conditions exist in a given system and what to do about them. A single let flat with no stored water is a short assessment. A block of flats, a school, a care home or an office with tanks, cylinders and many outlets is a larger job. Both are assessed to the same standard.

There is no single Act of Parliament named for Legionella. The duty comes from general health and safety law, principally the Health and Safety at Work etc. Act 1974 and the Control of Substances Hazardous to Health Regulations 2002, supported by the Management of Health and Safety at Work Regulations 1999. The duty sits with the employer, the self-employed person, or whoever is in control of the premises.

The Health and Safety Executive explains how to meet those duties in the Approved Code of Practice known as ACOP L8, fourth edition, 2013. It is not legislation, but it carries a special legal status: where relevant provisions were not followed, the duty holder must show compliance was achieved some other way. Supporting technical detail for hot and cold water systems sits in HSG274 Part 2.

In practice the responsible person must arrange a suitable and sufficient assessment, make sure the assessor is competent, act on the findings, and keep records. The assessment documented on this page is the starting point of that process, not the whole of it.

Every relevant water system needs an assessment, though not every system needs elaborate controls. An existing assessment should be reviewed regularly and redone whenever there is reason to believe it no longer describes the system. The usual triggers are set out below.

A new duty or a new tenancy. Landlords and agents should have a current assessment before a new tenant moves in, particularly after a void period.

Stored cold water. A system with a storage tank carries more consideration than one fed directly off the mains, because the water sits, warms and collects debris over time.

Dead legs and redundant pipework. Capped branches left after a refurbishment hold water that never moves and are a common finding on commercial systems.

Changes to the system. New pipework, a replaced tank, a new cylinder or a change of use or occupancy can all invalidate the previous assessment.

Vacancy or reduced use. After a building stands empty or lightly used, cleaning, flushing and chlorination are often needed before the system returns to normal service.

Drifting control readings or a poor sample. Temperatures out of range or a laboratory result above the accepted level mean the assessment and the control measures need review.

Higher-risk occupants. Care homes, healthcare settings and schools warrant closer attention and more frequent review.

As a baseline, many managed systems are reviewed around every two years, with higher-risk systems reviewed sooner. The interval is set by the risk assessment for the building, not by a fixed statutory deadline.

The assessment looks at the whole water system, how it is used, and who could be exposed. The points examined include:

Temperatures are taken at representative outlets during the visit. The findings are recorded system by system so a third party can follow the reasoning behind each one.

You receive a written report setting out the system as found, the conditions identified, and the reasoning behind each finding. Findings are categorised so it is clear what needs attention now and what can be planned in. The report is accompanied by a prioritised list of recommended actions and monitoring, and a statement of the level of risk identified for the compliance file.

The written report describes the system, the risks found and the basis for each finding. The recommendations cover maintenance, remedial work or monitoring as appropriate. On a low-risk system the report may confirm that no further action is required beyond the existing controls.

The report alone does not discharge the duty. That is done by acting on the findings, keeping the records, and reviewing the assessment when the system or its use changes. Records, including the assessment, monitoring entries, sample results and remedial work, belong together in the water safety file, where a managing agent, insurer or enforcing officer can be shown them.

Testing is the laboratory analysis of water samples to establish whether Legionella bacteria or other indicators are present. It is not automatically required in every building. The risk assessment decides whether sampling is needed, from which points, and how often. Where sampling is needed, samples are collected using an appropriate procedure and submitted for analysis, with results reported and explained and recommendations made for further investigation or treatment if required. See water testing and sampling.

Day-to-day control sits in a small number of measures. Temperature control keeps hot water hot and cold water cold. Documented flushing routines keep little-used outlets from standing. Periodic tank inspection keeps sediment, corrosion and lid defects from building up. A log book holds the assessment, the monitoring entries, the sample results and any remedial work. A named responsible person sees that the written scheme is carried out.

Where the assessment or a sample result shows a system is not under control, disinfection brings it back. Depending on the findings this may mean chlorination of the system, pipework disinfection, water tank cleaning, or a combination. Remedial work is scoped from the findings rather than sold as a fixed package.

We support properties of different sizes across London, including Islington, Chelsea, Kensington, Camden Town, the City of London, Hammersmith and Hackney. We are open Monday to Sunday, 8:00am to 6:00pm.