Legionnaires Disease

Legionnaires’ disease is a potentially fatal form of pneumonia caused by Legionella bacteria. Legionella bacteria are naturally found in water and as a result can enter man-made water systems. Under certain conditions the bacteria can grow and multiply. Infection can occur by breathing in small droplets/aerosols of water contaminated by the bacteria. Conditions that encourage Legionella growth include: 

  • Water temperatures in the range 20 – 45 degrees Celsius. 
  • Water stagnation – for example, if there is poor daily turnover of water, lack of water use or flushing or if there are dead legs in the water system. 
  • Presence of nutrients such as scale, sediment, rust, dirt. For example, if a water system has been drained down, rust may have developed. 

For some businesses, it has been over a year and a half since anyone has entered the building, while others have had reduced occupancy and may be at increased risk. If water is left standing in plumbing systems and storage tanks for too long, harmful bacteria can grow and multiply, causing serious illness such as Legionnaires’ disease when re-used again. Employers need to consider whether they have adequately controlled the risk of Legionella.  

Bringing your water systems safely back into use 

  • Flush water pipes by running taps until the water temperature is constant and mains water is drawn through the system 
  • Clean all drinking water outlets with suitable disinfectants 
  • Flush all toilets, and run water through sinks and shower basins, to ensure that the water trap seal is replenished in the u-bends 
  • Inspect all storage tanks and cisterns, and drain, clean, disinfect and refill as necessary; 
  • Clean shower-heads with disinfectant and flush water through until clean, with a minimum temperature of 60°C for hot water showers 
  • Empty hot water tanks and refill with water heated to 70° C for at least an hour before use 
  • Replace filter cartridges in water filters and clean & disinfect the cartridge holder according to manufacturer’s instructions, then run water through to flush clear 
  • Check pumps on the building’s water/wastewater system to ensure that they are operating correctly 
  • Check sewer & drains and clear any blockages promptly 
  • On-site wastewater treatment systems should be checked to ensure they are operating correctly 

The Health Safety Authority provide employers with guidance and advice for removing the risk of Legionnaires’ disease in their workplace. For advice, view the HSA's guidance on the Control of Legionella. If you have any further questions you can contact Emma Crowley on 01 605 1668 or at emma.crowley@sfa.ie  

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