Legionella Water Testing – Approved Code of Practice L8

The UK’s Health & Safety Executives (HSE) Approved Code of Practice (ACoP) "Legionnaires' disease: Control of legionella bacteria in water systems" (L8) recommends that routine testing for legionella bacteria in wet cooling systems be carried out at least quarterly, and more frequently when a system is being commissioned, or if the bacteria has been identified on a previous occasion.

Hot Water Systems

For hot water systems legionella testing is only recommended in particular circumstances, which are as follows:

  • where water temperatures are reduced as a consequence of using alternative biocide treatments. Sampling should be done initially on a monthly basis, with the interval increased depending on the level of confidence in control measures;
  • in systems where the control parameters (whether temperature or biocides) are not being achieved (frequency as required);
  • when an outbreak is suspected or has been identified (frequency as required);
  • possibly in hospital wards for immunologically suppressed patients.

Parts of this document © Crown Copyright - originally produced and published by the UK's Health & Safety Executive.

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