What happens if a Legionnaires disease risk assessment identifies significant findings?
Significant findings mean that the water system has conditions that could allow Legionella to grow or spread, or that existing precautions are not sufficiently reliable. The findings should be translated into a prioritised action plan, with each action assigned to a named person and supported by evidence that it has been completed and verified.
First, the level of risk should be interpreted. Not every finding presents the same degree of urgency. The assessment should consider factors such as water temperatures, areas of stagnation, storage tank condition, system complexity, aerosol-generating outlets and the susceptibility of people who may be exposed. A specialist may recommend immediate restrictions where there is a credible and urgent exposure risk, particularly in settings used by vulnerable people.
Immediate precautions may be needed. Depending on the finding, these could include taking an outlet or part of a system out of use, preventing access to contaminated areas, avoiding activities that generate aerosols, increasing temperature controls, or arranging cleaning and disinfection. Any temporary measure should be documented, communicated to affected staff and users, and kept in place only while a suitable permanent solution is implemented.
Remedial work should address the underlying cause. Typical measures may include:
- removing redundant pipework, dead legs and rarely used outlets;
- correcting faults affecting hot-water storage, distribution or return temperatures;
- cleaning and disinfecting tanks, calorifiers, pipework or outlets where contamination or poor condition has been identified;
- repairing insulation, valves, thermostatic mixing arrangements, pumps and other components that affect control;
- improving flushing arrangements for low-use parts of the system; and
- updating system drawings, asset records and outlet schedules where the installation is poorly understood.
The appropriate response depends on the evidence. Replacing equipment without dealing with stagnation, inadequate maintenance or incorrect system operation may leave the underlying risk in place. Conversely, unnecessary alterations can introduce new weaknesses if they are not designed and commissioned properly.
Responsibilities should be made explicit. The responsible person should confirm who will authorise work, arrange competent contractors, supervise temporary controls and check that recommendations have been completed. Where several organisations share a building or water system, their respective duties and areas of control should be recorded rather than assumed. Staff involved in operation, monitoring and maintenance should understand any revised procedures.
Testing can support decisions, but it is not a substitute for control. Where sampling is recommended, samples should be collected from representative points using a suitable method and sent to a competent laboratory. Results need to be considered alongside the physical condition and operation of the system. A negative sample does not remove the need to maintain effective temperature, cleanliness, circulation and usage controls, while a positive result should be assessed in context and may require further investigation or treatment.
Completion should be verified. Evidence may include temperature records, photographs, cleaning or disinfection certificates, updated schematic drawings, commissioning information, maintenance records and follow-up test results. The verifier should check that the work achieved its intended control, not merely that a contractor attended or a component was replaced.
Once the remedial measures have been completed, the control scheme should be amended to reflect the system as it now operates. This may involve changing monitoring points, inspection frequencies, flushing instructions, responsibilities or escalation arrangements. Findings should also be considered after alterations to the water system, a change in building use, periods of low occupancy, changes in the population at risk or evidence that controls are failing.
If significant findings are not acted upon, the organisation may be unable to demonstrate that it has managed foreseeable exposure risks appropriately. Clear records of the finding, the decision taken, the person responsible, the completion date and the verification evidence provide an auditable account of how the risk was dealt with.
A significant finding does not automatically mean that Legionnaires’ disease is present or that the system is contaminated. It means the assessment has identified a condition that could undermine control of Legionella, such as unreliable temperature management, poor system understanding or a pattern of low use. The appropriate next step depends on the evidence and the potential for exposure.
This distinction matters because remedial action should be proportionate and targeted. A temperature-control fault may require engineering attention and closer monitoring, while an unneeded section of pipework may need removal. Cleaning or disinfection should be undertaken where the assessment supports it, rather than treated as a universal response to every finding. If illness is suspected, the matter should also be referred through the appropriate public health and occupational health processes; a risk assessment alone cannot diagnose an infection.
Discuss your Legionnaires disease risk assessment findings
Discuss the assessment findings with a competent water hygiene specialist to clarify priorities, responsibilities and the evidence needed to close each action. Blue Fish Water Management Ltd can provide practical advice on the next steps following a Legionnaires disease risk assessment.