Appendix 1 - risk management system

When inspecting or investigating, Inspectors should look at the Legionella risk management system:

Risk assessment

The ACOP L8 and COSHH places responsibility on employers and others to:

  1. identify a competent person;
  2. identify and assess risks of Legionellosis; who may be harmed, what risk does the hot and cold water system pose, what controls exist to reduce the risk;
  3. avoid the use of systems that give rise to a reasonably foreseeable risk of Legionellosis or, where this is not reasonably practicable, prepare a written scheme for minimising the risk from exposure;
  4. implement and manage the scheme of precautions including the appointment of a person, or persons, to take managerial responsibility and to provide supervision; and,
  5. keep appropriate records.

The assessment should address the risks from the system and how they are controlled. It should include details of:

  • management responsibilities;
  • a current / up to date schematic of the system (where necessary to identify redundant pipe work (eg dead legs), sentinel outlets (ie nearest and furthest outlets in each loop or run), monitoring points, storage cylinders / tanks, etc.);
  • details of precautions taken including the control method/s;
  • inspection and maintenance programme (eg checking the system is kept clean and at correct temperatures);

Records of operation, monitoring and remedial work should be kept.

If water treatment or any other task is performed by a contractor then the respective responsibilities of the occupier and the contractor must be clear.

Control measures

A summary of the main requirements for a hot and cold water system utilising temperature as the means of Legionella control can be found in Appendix 3 and below.

Cold Water Storage tank

  • The tank should ideally be sized to supply no more than one day's water usage;
  • The tank should ideally be sited in a cool place;
  • The tank should be thermally insulated to protect from extremes of heat and to maintain suitable temperatures;
  • The tank should possess a tight fitting lid;
  • The water over flow pipe should be fitted with an insect screen;
  • The water surface should be clean and not contain any debris or contamination;
  • The incoming water temperature should be no more than 20°C;
  • Access should be provided for inlet valve maintenance, inspection and cleaning.

Hot Water Storage Cylinder

  • The cylinder should ideally be sized to provide the water typically needed for a day's usage;
  • The cylinder should be insulated;
  • The cylinder should deliver outgoing water at a temperature of at least 60°C and a gauge should be fitted at the outlet of the cylinder to ensure this is being achieved (attaining acceptable temperatures may be difficult to achieve if the storage cylinder is not of an adequate size);
  • The hot water circulation loop should be designed to give a return temperature to the cylinder of at least 50°C and a gauge should be fitted at the return to the cylinder to ensure this is being achieved;
  • The vent pipe from the cylinder, which allows for the increase in volume of the water, should be large enough and suitably sited to prevent hot water being discharged. However, if it is discharged, the water should go to a tundish/drain rather than to the cold water tank;
  • The cylinder should have a drain valve located in an accessible position at the base of the cylinder so accumulated sludge can be drained easily;
  • Large calorifiers, should be fitted with devices which will prevent prolonged temperature stratification of the stored water (eg a time controlled shunt valve)

Hot and Cold Water Distribution System

  • Hot and cold water distribution pipes should be insulated, where required, to ensure that cold water pipes remain cold and hot pipes remain hot and to minimise heat transfer between the two;
  • Low use cold water outlets should be installed upstream of higher use outlets to maintain frequent flow, wherever possible;
  • Thermostatic mixing valves (TMVs), where fitted, should be located as close as possible to the point of use;
  • The water temperature at the hot outlets should be measured, at least monthly, to ensure it reaches at least 50°C within a minute of running the water. If TMVs* are fitted the temperature of the hot inlet pipe, just prior to the TMV, should be measured to ensure it reaches at least 50°C;
  • Trace heating should be supplied on a non-recirculatory hot water system where the temperature would not otherwise reach 50°C in one minute;
  • The water temperature at the cold outlets should be below 20°C after running the outlet for up to two minutes;
  • Redundant distribution pipe work should be removed or cut back as far as possible to a common supply;
  • Materials which encourage growth of Legionella (eg flexible hoses) should be avoided wherever possible.
  • Materials which encourage growth of Legionella (eg flexible hoses) should be avoided wherever possible.

*Note - TMVs should ideally only be used where people are at risk of scalding


It is essential that the control measures identified are maintained long term to minimise bacterial growth. In addition:

  • storage tanks and cylinders should be cleaned periodically,
  • any tank, cylinder or pipe insulation should be maintained to ensure effectiveness,
  • shower heads and hoses should be dismantled, cleaned and de-scaled at least quarterly,
  • infrequently used outlets should be flushed through to drain for several minutes at least weekly,
  • records of temperatures at cylinders, tanks and sentinel outlets (ie nearest and furthest outlets on each loop or run) should be kept

Where failures are found, a robust system should be in place to ensure corrective action is taken.


Staff involved in maintaining hot and cold water systems must understand the risks and the precautions needed to control them. A nominated competent person should be appointed to oversee the management of Legionella risk at care settings. This person should be competent to ensure that the risk is adequately assessed and controlled so far as is reasonable practicable.

They should have sufficient authority to ensure that the controls identified through the assessment are properly implemented and maintained. Competent persons need to be aware of systems or equipment that requires specific maintenance or cleaning to ensure it remains effective.

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