Legionella Risk Assessments

A Legionella risk assessment is a site-specific document that details the findings of an 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.

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 Service 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 new information about risk or control measures have become available
  • Where monitoring indicates that control measures are no longer effective

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

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].

Temperature measurements would be completed, checked and evaluated. The following standards should be met:

  • Hot water storage at above 60°C
  • Hot water at discharge points above 50°C within one minute of running
  • Cold water storage at below 20°C
  • Cold water at discharge points at below 20°C within two minutes of running
  • A colour schematic drawing will be produced showing pipe links between key plant assets, and building water distribution [Blue = Mains Water, Green = Tank Water, Red = DHWS].

Where hot water is discharged at more than 50oC and there is a risk of scalding the risk assessment should identify the need for thermostatic mixing valves or other forms of temperature control.

Any areas requiring remedial action would be covered in the recommendations.