SC38 - Legionella
06 Dec 2010



STFC Safety Code No 38




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Initial ReleaseSeptember 2010
1.1Minor change to ScopeFebruary 2011
1.2Minor change to para 4.1.1December 2011
1.3Addition of separate Appendix 8February 2014
Add Document Retention Policy Appendix
August 2014
Changes to section 4.3 to clarify potential for legionella incubation and maintenance requirements.April 2016
Changes to establish Site Water Safety Group’s and their terms of reference; update legislation references, and separate the Hydrop guidance for ISIS Cooling Towers and Evaporative Condensers (R11 and R80) from the general STFC water safety plan.
June 2017
​Rationalisation of appendices 1, 2 & 8
​October 2018
​Added Appendix for Closed Loop water systems
​July 2019
​Updated Appendix 2 added
​February 2020​​

1. Purpose

Legionella are a range of bacteria widespread in natural fresh water which can if they proliferate cause Legionnaires' disease or Legionellosis - potentially fatal forms of pneumonia. In the UK there are between 200 and 300 cases per year of which approximately 30 are fatal.

While the ecology of Legionella in water systems is not fully understood, in the laboratory, it will grow optimally in stagnant nutrient rich water in the temperature range 20°C to 45°C (37°C body temperature) and pH 6.5-7.5. Water contaminated by Legionella only presents a risk when it is dispersed in air in the form of an aerosol (very fine water droplets / spray) such as that from a shower. Legionnaires' disease can therefore be contracted where there are opportunities to inhale infected water droplets.

Legionnaires' disease is a statutorily reportable disease.

There is no health and safety legislation specific to the management of Legionella, rather it is addressed through general duties defined under the:

  • Health and Safety at Work etc. Act 1974, Sections 2, 3 and 4;
  • Management of Health and Safety at Work Regulations 1999, particularly Regulations 2, 3, 4 and 6;
  • Control of Substances Hazardous to Health Regulations (COSHH) 2002, particularly Regulations 6, 7, 8, 9 and 12, where the definition of hazardous substances includes harmful micro-organisms;
  • Notification of Cooling Towers and Evaporative Condenser Regulations, 1992;
  • Public Health (Infectious Diseases) Regulations 1988.
  • The Water Supply (Water fittings) Regulations 1999;
  • The Water Supply (Water Quality) Regulations 2010; and
  • Food Safety Act 1990.

An HSC Approved Code of Practice (ACOP) 'Legionnaires Disease - The control of Legionella bacteria in water systems', L8 (Fourth Edition) and HSG247 Part 1, offers specific guidance for managing the risk from Legionella bacteria.

The present code establishes STFC standards and arrangements for the management and control of Legionella risks at STFC premises minimising, avoiding or preventing infection.

2. Scope

The present code applies to the design, operation and maintenance of all water systems where there is the potential for Legionella to grow and become dispersed as a respirable​ aerosol, whether owned or managed by the STFC or brought onto STFC sites by facility users, tenants; contractors or other visitors.

The sources include, but are not limited to, the following domestic or non domestic systems:

  • Cooling Towers;
  • Hot Water Calorifiers (primary heating coil, electric immersion heater or otherwise);
  • Cooling systems for scientific equipment; 
  • Fixed and mobile air conditioning, dehumidification or ventilation systems and humidifiers;
  • Water Storage Tanks;
  • Domestic or emergency showers or eye wash stations;
  • Water features or fountains, including drinking fountains;
  • Sprinkler Systems, hose reels;
  • Car Washes;
  • Machine Tool Coolant Systems e.g. lathes etc.;
  • Fire fighting systems for example sprinkler systems, hoses and reels;
  • Machine Tool coolant systems e.g. lathes etc.; and
  • Hot and Cold Water systems, domestic and industrial.

3. Definitions

3.1 Cooling Tower

Apparatus through which warm water is discharged against an air stream, in doing so part of the water is evaporated to saturate the air, and this cools the water. The cooler water is usually pumped to a heat exchanger to be reheated and recycled through the tower.

3.2 Dead Leg

Pipes leading to a fitting through which water only passes when there is draw-off from the fitting.

3.3 Dip Slide

A testing device for the microbial content of liquids. It consists of a plastic carrier bearing a sterile culture medium which can be dipped in the liquid to be sampled. It is then incubated to allow microbial growth. The resulting microbial colonies and number are estimated by reference to a chart.

3.4 Drift Eliminator

More correctly referred to as drift reducers or minimisers this equipment contains a complex system of baffles designed to remove water droplets from cooling tower air passing through it.

3.5 Evaporative Condenser

A heat exchanger in which refrigerant is condensed by a combination of air movement and water sprays over its surface.

3.6 Legionella Responsible Person (LRP)

A person who has been formally appointed, in accordance with the HSE Approved Code of Practice, to assume managerial responsibility for implementation of the Legionella precautions and the responsibilities detailed in this SHE code.

3.7 Sentinel Tap

For a hot water services this is the first and last taps on a re-circulating system. For cold water systems (or non-re-circulating hot water systems) they are the nearest and furthest taps from the storage tank. The choice of sentinel taps may also include other taps which are considered to represent a particular risk.

3.8 Water Safety Group (WSG)/Steering Group

A multidisciplinary group formed to undertake the commissioning, development, implementation and review of the water safety plan. The aim of the Water Safety Group is to ensure the safety of all water used by residents, staff and visitors, to minimise the risk of infection associated with water, including legionella.

4. Responsibilities

4.1 Head of Estates ​shall:
  • 4.1.1 ensure that one or more suitably trained and experienced Legionella Responsible Persons (LRPs), and deputies, are appointed in writing and provided with the resources to manage Legionella hazards within defined areas of responsibility, as appropriate discussing their appointment with other Directors where such hazards exits, see Appendix 5. The names of such appointments should be recorded in the SHE Directory.
    4.1.1 ensure that one or more suitably trained and experienced Legionella Responsible Persons (LRPs), and deputies, are appointed in writing and provided with the resources to manage Legionella hazards within defined areas of responsibility, see Appendix 5. The names of such appointments should be recorded.
  • 4.1.2 ensure Site Water Safety Groups are established to review Legionella management at each STFC site, see Appendix 8​.
4.2 Legionella Responsible Person shall:
  • 4.2.1 ensure that effective arrangements are implemented for the assessment and management of the Legionella risks within their area of responsibility, see App​endix1Appendix 2, Appendix 3 and Appendix 4.
  • 4.2.2 as appropriate, ensure one or more suitably qualified and experienced persons or Legionella management contractors are appointed for water systems treatment and maintenance to undertake the duties detailed in this code on their behalf . Where contractors are employed they shall be registered with the Legionella Control Association. The competence and performance of those undertaking these activities should be reviewed regularly and documented.
  • 4.2.3 ensure that a documented register of all water systems, including cooling towers and evaporative condensers, is established, maintained and regularly reviewed, see Appendix 5.
  • 4.2.4 ensure that all existing or new cooling towers or evaporative condensers are registered with the local environmental health authority in writing detailing the type and location of the facility. A copy of their notification should be retained. Where cooling towers or evaporative condensers are made redundant, decommissioned or demolished, inform the local environmental health authority in writing retaining a copy of the notification.
  • 4.2.5 ensure that documented risk assessments are conducted for systems detailed in the water systems register within their area of responsibility. Risk assessments should determine whether potential for harm or exposure is reasonably foreseeable and as appropriate detailing the control measures necessary to prevent or minimise the risk from Legionella exposure, see App​endix1Appendix 2, Appendix 3 and Appendix 4​.

    Legionella Risk Assessments should be reviewed every 2 years, or whenever significant changes or modifications to water systems occur or in the light of the results of Legionella monitoring programmes.
  • 4.2.6 ensure that documented "Written Schemes", based on risk assessments are created to outline the controls for preventing, reducing, controlling and monitoring Legionella hazards. The scheme should describe the correct operation of the water system and persons responsible for carrying out actions, see App​endix1Appendix 2, Appendix 3 and Appen​dix 4, including:
    • An accurate schematic diagram of the system, updated whenever there is a significant change;
    • System commissioning, shutdown and re-commissioning procedures and precautions;
    • System checks and frequencies to determine the effectiveness of Legionella controls and warning of system malfunction;
    • Maintenance requirements and frequencies; and
    • Remedial actions to be taken in the event of system malfunction or Legionella outbreak.
  • 4.2.7 ensure that all records relating to the management of Legionella are retained for at least 5 years, including but not limited to test results, inspection records, maintenance records, contractor training records etc, see Appendix 6.
  • 4.2.8 ensure that the design of new water systems, or equipment containing water, considers the hazards arising from Legionella in order that the risks are eliminated or minimised.
  • 4.2.9 as appropriate supervise the contracts for water system treatment and maintenance of cooling towers, and hot and cold water systems.
  • 4.2.10 immediately report any instances of increased risk (e.g. high bacterial or other pathogen counts) or Legionella outbreak to the SHE Group, see STFC SHE code 5 Reporting and Investigationon of SHE Incidents.
  • 4.2.11 ensure that Site Water Safety Groups are established and operated as per ToR, see Appendix 9​​.
4.3 Managers, including those responsible for the design, construction or operation of water containing systems shall:
  • 4.3.1 inform and seek the advice of the LRP in respect of: work on or modifications to existing water equipment/systems or their design; or any new water equipment/systems and their design and installation, that may pose the risk of Legionella incubation, see Appendix1Appendix 2, Appendix 3 and Appendix 4
  • 4.3.2 ensure that all staff, users, contractors or other visitors working in areas, or undertaking activities, where Legionella hazards could exist or could be introduced into existing water systems are made aware of potential hazards and controls detailed in the relevant Risk Assessments and Written Schemes. It is likely also that there are other hazards present where Legionella controls are employed, for example: scalding; COSHH; and environmental disposal hazards.

    See STFC SHE Code 15 - Contractor Management, and STFC SHE Code 19 - Work on buildings premises, services and infrastructure.

    STFC staff working in such areas should be trained, see Appendix 6, and evidence of training and competence sought from contractors.
  • 4.3.3 report all incidents or near misses related to the management and control of Legionella, see STFC SHE code 5 - Reporting and Investigation of SHE Incidents. Report all actual or suspected cases of Legionnaires disease in staff or others working on STFC sites immediately to the STFC SHE Group and Occupational Health teams.
4.4 SHE Group shall:
  • 4.4.1 Report all instances of Legionnaires disease to local environmental health authorities, and the HSE under the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations (RIDDOR), 1995. See Appendix 7.
  • 4.4.2 ensure that an audit of the implementation of this SHE code is undertaken, as appropriate by the appointed Legionella management contractor, at least every 3 years, see STFC SHE Code 30 - SHE Auditing and Inspection. This shall be in addition to any local audit/inspection programmes undertaken against relevant guidelines and approved codes of practice more frequently. 

5. References

Electronic copies of legislation, approved codes of practice and British Standards can be accessed by STFC staff through STFC-wide subscriptions for online information resources. These services are provided by the Chadwick and RAL libraries and further details can be found on the SHE Group website.

  • 5.1 The Water Regulations Advisory Scheme’s (WRAS) ‘Water Regulations Guide’, and any other requirements of the local water undertaker;

    5.2 The Water Supply (Water fittings) Regulations 1999.

    5.3 The Water Supply (Water Quality) Regulations 2000.

    5.4 HSE Legionnaires’ disease The control of legionella bacteria in water systems. Approved Code of Practice and guidance on regulations: L8 (Fourth edition) Published 2013

    5.5 HSE Legionnaires’ disease: Technical guidance Part1: The control of legionella bacteria in evaporative cooling systems: HSG274 Part 1 Published 2013

    5.6 HSE Legionnaires’ disease Part 2: The control of legionella bacteria in hot and cold water systems: HSG274 Part 2 Published 2014

    5.7 HSE Legionnaires’ disease: Technical guidance Part 3: The control of legionella bacteria in other risk systems: HSG274 Part 3 Published 2013

    5.8 BS 1710 – 1984 - Specification for identification of pipeline services.

    5.9 BS 8558:2015 provides complimentary guidance to BS EN 806 . It is a guide to the design, installation, testing, operation and maintenance of services supplying water for domestic use within buildings and their curtilages.

    5.10 BS EN 806-5:2012 Specification for installations inside buildings conveying water for human consumption - Operation and maintenance.

    5.11 BS EN 806-1:2000 Specifications for installations inside buildings conveying water for human consumption -General.

    5.12 BS EN 806-2:2005 Specifications for installations inside buildings conveying water for human consumption – Design.

    5.13 BS EN 806-3:2006 Specifications for installations inside buildings conveying water for human consumption - Pipe sizing. Simplified method.

    5.14 BS EN 806-4:2010 Specifications for installations inside buildings conveying water for human consumption – Installation.

    5.15 BS 8551-2015 Provision and management of temporary water supplies and distribution networks

    5.16 BSI PD 855468-2015 Guide to the flushing and disinfection of services supplying water

    5.17 BS 8558-2015 Guide to the design, installation, testing and maintenance of services

    5.18 BS EN ISO 5667-1 2006 Water Quality – Sampling

    5.19 BS 8554 2015 - Code of practice for the sampling and monitoring of hot and cold water services in buildings

    5.20 BS7592:2008 – Sampling for Legionella bacteria in water systems – Code of practice.

    5.21 BS 8580:2010 – Water Quality – Risk assessments for Legionella Control – Code of Practice.

    5.22 PWTAG Code of Practice 1.13v5_000​

Contact: Baker, Gareth (STFC,DL,COO)