Legionella Risk Assessment, Testing & Control in Ireland

The Legal Duty: Who Must Assess for Legionella in Ireland?

The Safety, Health and Welfare at Work Act 2005 places a general duty on employers and those in control of premises to identify hazards and manage associated risks. The Health and Safety Authority (HSA) identifies Legionella as a biological agent covered by the Safety, Health and Welfare at Work (Biological Agents) Regulations 2013 and its subsequent amendments.

The practical standard applied in Ireland draws heavily on the UK Health and Safety Executive's Approved Code of Practice L8 ('Legionnaires' disease: The control of legionella bacteria in water systems') and its associated technical guidance HSG274 (Parts 1, 2 and 3), which are recognised as the definitive technical standards for legionella control in water systems. The HPSC (Health Protection Surveillance Centre) also publishes guidance on Legionnaires' disease investigation and control.

Duty holders who must carry out a legionella risk assessment include:

• Employers with water systems on their premises (hot and cold water, cooling towers, process water)
• Commercial landlords and property managers with buildings in multiple occupation
• Healthcare facilities - hospitals, nursing homes, GP practices
• Hotels, guesthouses, and hospitality premises
• Manufacturing and industrial sites with cooling towers or evaporative condensers
• Food and beverage production facilities
• Educational institutions - schools, colleges, universities
• Facilities management companies with managed premises portfolios

The written risk assessment must be produced by a competent person - someone with sufficient training, knowledge, and experience to identify the risks associated with the water systems in question. Halpin & Hayward provides competent-person legionella risk assessment for all of the above sectors.

What a Legionella Risk Assessment Covers

1. Water System Survey and Schematic

The assessment begins with a physical survey of all water systems in the premises. This produces a schematic drawing showing the layout, components, and flow of the hot and cold water distribution system and any other water systems (cooling towers, spa pools, decorative fountains, process water). The survey identifies:

• All water storage vessels (cold water storage tanks, calorifiers, buffer vessels)
• Dead legs, infrequently used outlets, and areas of low flow
• Temperature control points and their current performance
• Materials in contact with water - risk of biofilm formation
• Cooling towers, evaporative condensers, and humidifiers

2. Risk Evaluation

The assessor evaluates the risk that each element of the water system presents for Legionella growth and dispersal. Key risk factors include water temperature (particularly temperatures in the Legionella growth range of 20-45°C), stagnation, and the presence of conditions that support biofilm. The evaluation produces a risk rating for each system.

3. Written Risk Assessment Document

The written assessment documents the survey findings, risk ratings, and the control measures required for each system. This is the legal record required by the duty holder. It must include:

• Identification of all water systems and their risk of Legionella
• A description of the control measures in place and any gaps identified
• The name and competence of the person who carried out the assessment
• The date of the assessment and the date by which it should be reviewed

4. Control Scheme and Monitoring Log

Following the risk assessment, Halpin & Hayward designs and implements a written control scheme appropriate to the assessed risk. This includes temperature monitoring schedules, chemical dosing programmes, cleaning and disinfection intervals, and a monitoring log that the duty holder must maintain. The scheme must be kept up to date and reviewed whenever there is reason to believe it is no longer valid (e.g. after building modifications, system changes, or following an incident).

Legionella Water Sampling and Testing

Water sampling and microbiological testing is the primary method of verifying that Legionella control measures are working. Halpin & Hayward carries out water sampling in accordance with HSG274 Part 2 (Hot and Cold Water Systems) protocols, including:

• Representative samples from sentinel taps (first-draw and after 2-minute flush), tank outlets, calorifier outlets, and showers
• Cooling tower basin water and drift eliminator swabs
• Biofilm swabs from internal surfaces where accessible

Samples are dispatched to an accredited INAB laboratory for analysis using standard culture methods (ISO 11731) and, where appropriate, quantitative PCR (qPCR) for faster results. Results are reported against the action levels defined in L8/HSG274:

Legionella Control: Hot & Cold Water Systems

The primary control strategy for hot and cold water systems is temperature. L8 and HSG274 specify that cold water should be stored and distributed at or below 20°C, and hot water should be stored at 60°C or above and distributed at 50°C or above within one minute of running. Temperature monitoring at sentinel outlets is required at least monthly.

Where temperature control alone is insufficient, supplementary chemical disinfection (silver-stabilised hydrogen peroxide, chlorine dioxide, or continuous chlorination) may be required. Halpin & Hayward designs and installs chemical dosing systems for hot and cold water systems where risk assessment indicates this is necessary.

Dead Legs and Infrequently Used Outlets

Dead legs (sections of pipework with no regular throughput) and infrequently used outlets (e.g. showers in rooms that are rarely occupied) are the most common cause of Legionella proliferation in hot and cold water systems. The control strategy is physical removal of dead legs where possible, and a regular flushing regime (at least weekly) for low-use outlets. Halpin & Hayward's monitoring programme includes a flushing register and can manage this on behalf of facilities teams.

Legionella Control: Cooling Towers & Evaporative Condensers

Halpin & Hayward provides a full cooling tower Legionella management service:

• Annual risk assessment and inspection per L8/HSG274 Part 1
• Continuous biocide dosing programme with automated chemical feed
• Monthly water sampling and analysis
• Quarterly cleaning and disinfection
• Drift eliminator inspection and maintenance
• Registration support with local authority (Environmental Health)

Remediation and Disinfection

Where Legionella is detected above action levels, or where a system is found to be non-compliant on risk assessment, Halpin & Hayward provides emergency remediation and disinfection services. This includes thermal disinfection (raising hot water temperatures to 70°C+ and flushing all outlets), chemical disinfection (hyperchlorination, chlorine dioxide treatment, or hydrogen peroxide dosing), and physical cleaning of tanks, calorifiers, and distribution pipework.

Following remediation, confirmation sampling is carried out to verify that Legionella levels have returned to satisfactory levels before the system is returned to service.

Sectors Served

Frequently Asked Questions

• Who is responsible for legionella risk assessment in a commercial building in Ireland?

  The duty holder - typically the employer, building owner, or person in control of the premises - is responsible for ensuring a legionella risk assessment is carried out and that appropriate control measures are in place. The duty cannot be delegated away, but the practical work of carrying out the assessment and implementing control measures can be contracted to a competent water treatment specialist. Halpin & Hayward acts as competent person for duty holders across Ireland.

• How often should a legionella risk assessment be reviewed in Ireland?

  A legionella risk assessment should be reviewed whenever there is reason to believe it may no longer be valid - for example, after building modifications, changes to the water system, following a positive Legionella test result, or after a period of shutdown. In the absence of any changes, an annual review is considered good practice and is the default recommendation in L8/HSG274. Water sampling frequency (typically quarterly for higher-risk systems, annually for lower-risk) is specified in the control scheme produced after the assessment.

• What is the difference between a legionella risk assessment and a legionella test?

  A legionella risk assessment is a systematic review of a water system to identify risks, document control measures, and produce a written scheme for ongoing management. It is carried out by a competent assessor and produces a written document. A legionella water test (water sampling and microbiological analysis) is a monitoring activity - it takes physical samples from the water system and sends them to a laboratory to determine whether Legionella bacteria are present and at what concentration. Both are required: the risk assessment sets the framework; testing verifies that the framework is working.