Risk mitigation for Legionnaires’ disease

Your property will have been likely standing empty for many months now.  This poses a number of risks, but one of the main ones is the risk of legionella bacteria in the water system.

Legionellosis is a collective term for diseases caused by legionella bacteria including the most serious Legionnaires’ disease, as well as the similar but less serious conditions of Pontiac fever and Lochgoilhead fever. Legionnaires’ disease is a potentially fatal form of pneumonia and everyone is susceptible to infection. The risk increases with age but some people are at higher risk including:

  • people over 45 years of age
  • smokers and heavy drinkers
  • people suffering from chronic respiratory or kidney disease
  • diabetes, lung and heart disease
  • anyone with an impaired immune system

The bacterium Legionella pneumophila and related bacteria are common in natural water sources such as rivers, lakes and reservoirs, but usually in low numbers. They may also be found in purpose-built water systems such as cooling towers, evaporative condensers, hot and cold water systems and spa pools.

If conditions are favourable, the bacteria may grow increasing the risks of Legionnaires’ disease and it is therefore important to control the risks by introducing appropriate measures.

How do you get it?

Legionnaires’ disease is contracted by inhaling small droplets of water (aerosols), suspended in the air, containing bacteria.

Certain conditions increase the risk from legionella if:

  • the water temperature in all or some parts of the system may be between 20-45 °C, which is suitable for bacteria growth
  • it is possible for breathable water droplets to be created and dispersed e.g. aerosol created by a cooling tower, or water outlets
  • water is stored and/or re-circulated
  • there are deposits that can support bacterial growth providing a source of nutrients for the organism e.g. rust, sludge, scale, organic matter and biofilms

How can you prevent it?

  • If your property has been empty for a while, flush the whole water system for two minutes or more. First flush your toilet, then let the kitchen taps and the hand basin taps run for two minutes or more to flow both hot and cold water through the system. Next, flush the shower through as described below. Finally, let any other taps run for two minutes.
  • If your shower has not been used for a week or more, run water from both hot and cold supplies through the shower hose and showerhead for two minutes. To ensure no spray escapes from the showerhead, run it through a bucket of water or a bath full of water.
  • If your shower has not been used for two weeks or more, disinfect the showerhead. The showerhead should be removed and then run the shower for two minutes. The showerhead should be disinfected before being re-fitted by immersing for at least an hour in any solution designed for cleaning baby feeding bottles (e.g. Milton). Showerheads should be regularly disinfected about four times a year.
  • All toilets need flushing at least twice (with the lid down) to avoid spray and contamination. This empties the cistern, it refills, flush again and refills, ensuring that system has been throughly flushed through.
  • Increase the temperature of your water to 60°C or higher. Temperatures above 60°C will kill Legionella bacteria. If you are unsure of how to raise the temperature of your boiler safely, ask a gas boiler engineer to attend the property. Beware of burns and scalding and take extra care if you have children. Legionella can survive in low temperatures, but thrive at temperatures between 20°C and 45°C.
  • Ensure that in the room the furthest from the water inlet / tank you run their  taps and showers  for at least two minutes (to ensure fresh water is reaching this point) 
  • Wear a mask when dealing with the both hot and cold water flush through as Legionella lives in vapour 
  • When looking at equipment at your property don't forget the hosepipe if your property has one. If the hosepipe has been lying on the ground in the garden, the sun would have warmed the excess water in the pipe and could be a source for Legionella.

If you are unsure and would like further information please visit the HSE website https://www.hse.gov.uk/legionnaires/index.htm

For specific information on Spa Pools, take a look at this handy guide or discuss with your manufacturer.


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