Legionnaires' disease outbreak investigation toolbox

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Specimen engineering designs for cooling towers and condensers

Where to sample in an installation - general guide

(Refer also to guidance from L8 Legionnaires' Disease Health and Safety Executive paper [1]. Other member states might have their own versions of such guides.)

Cooling systems including cooling towers and evaporative condensers

Typical cooling tower

Red = return to cooling tower

Sampling cooling systems

  • Ideally sample from somewhere on the return to cooling tower
  • Neutralise biocides where possible, for more detail see [2]

Outbreak investigation samples from cooling systems should be taken:

  • From the warmest point
  • Possibly from the pond (furthest away from fresh water inlet ball valve if possible)
  • Supply water / Make up water
  • Foam (slime) from pack, and other components
  • Biofilm
  • Any others suggested by the risk assessment

  1. HSE (2008) Control of Legionella bacteria in water systems ISBN 978 0 7176 1772 2
  2. ENVIRONMENT AGENCY (2005) The determination of Legionella bacteria in waters and other environmental samples http