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Legionella Risk Assessment

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What is a Legionella Risk Assessment?

A Legionella risk assessment is a site-specific document that details the findings of a technical examination of the entire water system within the premises. The primary purpose is to identify if there are any parts of the system that might support or enable the growth of the Legionella bacteria and therefore present a risk to building users.

Is a Legionella Risk Assessment a legal requirement?

It is a legal duty for all employers, landlords, or premises to understand and manage Legionella risk within their workplace. They should also ensure that a Legionella Risk Assessment (LRA) of all water systems is carried out regularly.

What does a Legionella Risk Assessment cover?

The assessment takes into account the following factors:

  • Water temperature
  • Water stagnation
  • Potential for aerosol formation
  • Heat gain / loss potential
  • Condition of the water
  • Condition of the water services and the water system as a whole
  • The susceptibility of exposed persons
  • The Population Density of Exposed Persons

How often do I need a Legionella Risk Assessment?

The risk assessment should be reviewed regularly and whenever there is reason to believe the original assessment may no longer be valid, for example:

  • Where there have been changes to plant, the water system or its use
  • Where there have been changes to the use of the building
  • Where there has been an update in relevant legislation
  • Where monitoring indicates that control measures are no longer effective
  • Where a change of key personnel involved in legionella control at the site has happened
  • Where a building change from occupied to unoccupied (and vice versa).

Risk Assessment Specification

The following areas would be investigated:

  • Assessment of Management Records
  • System design, installation and materials
  • Operational and maintenance regime
  • Storage conditions of hot & cold water
  • System usage
  • Temperature measurement
  • Any dead legs, redundant or little used services
  • The Written Scheme (if applicable)
  • The purpose of the risk assessment is to evaluate the plant, equipment, operational and management of the building systems and their risk of bacteriological proliferation.

The risk assessment would include all hot and cold-water services, which will incorporate an assessment of the design, usage and condition. All information would be recorded on pro-forma forms and collated within a single comprehensive document (supplied in electronic format).

A colour schematic drawing would be produced showing pipe links between key plant assets, and building water distribution (Blue = Mains Water, Green = Tank Water, Red = Domestic Hot Water).

Who would carry out my Legionella Risk Assessment?

Your Legionella Risk Assessment would be carried out by a QES Ltd assessor. All QES Ltd assessors hold a relevant City & Guilds qualification in relation to Legionella Risk Assessment, this is supplemented by onsite training and competency checks.


 The building owner or manager has a duty of care and it is a legal obligation to carry out a Legionella Risk Assessment. Where there has been a failure to manage risk correctly this could result in prosecution and significant fines.

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