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The Technical Guidance for Legionella produced by the HSE has now been removed from the AcoP L8 (2013) and split into 3 separate chapters under the guise of HSG274. The 3 documents are available for free download on the HSE website as follows:

  • Part 1: The control of legionella bacteria in evaporative cooling systems
  • Part 2: The control of legionella bacteria in hot and cold water systems
  • Part 3: The control of legionella bacteria in other risk systems

Focussing on Part 2 now, the following table will help you identify the key differences proposed in the new guidance for maintaining hot and cold water systems:

Key Changes – Hot & Cold Water Systems

Item System Examples Details/ Changes
Monitoring Small DHW Storage Systems < 15-litres
  • Point of Use Water Heaters < 15-lires (POU)
  • Electric Water Heaters < 15-Litres (EWH)
  • Instant Water Heaters < 15-litres (IWH)
  • Not expected to store water at 60°C
  • Monitoring at nearest outlet between Monthly- 6 Monthly
  • Must achieve 50°C
Monitoring DHW Storage Systems > 15-litres
  • DHW Vessels & Calorifiers > 15-litres
  • Should store and flow water at 60°C or above
  • Return temperature should be > 50°C
  • Return temperature for Healthcare should be > 55°C
Combination Water Heaters
  • Point of Use Water Heaters < 15-lires (POU)
  • Electric Water Heaters < 15-Litres (EWH)
  • Instant Water Heaters < 15-litres (IWH)
  • Check water temperatures at an outlet monthly to confirm the heater operates at 55 -60°C.
  • Inspect, clean and disinfect cold water header annually
Cold Water Tanks
  • DCW Supply Tanks
  • DCW Booster Tanks
  • Cooling Tower Softened Water Makeup Tanks
  • Previously should test tank temperatures twice per year
  • Now only test once per year in summer
  • Storage temperature should be < 20°C
Hot Water Services (Circulating Systems)
  • Principal Return Legs of Larger DHW storage & distribution systems
  • Take temperatures at return legs of principal loops (sentinel points) to confirm they are at a minimum of 50 °C (55 °C in healthcare premises).
  • Temperature measurements may be taken on the surface of metallic pipework
Hot Water Services (Circulating Systems)
  • Sub-ordinate Return Legs of Larger DHW storage & distribution systems
  • Take temperatures at return legs of subordinate loops on a quarterly basis
  • Temperature measurements can be taken on the surface of pipes, but where this is not practicable, the temperature of water from the last outlet on each loop may be measured and this should be greater than 50 °C within one minute of running (55 °C in healthcare premises).
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