14 August 2017

Legionella in water supply

Legionella in your water supply is treatable, however having a legionella prevention plan is key to counteracting the potentially devastating effects of legionnaires’ disease. 

 Legionella pneumophilia is a bacterium. It can be found in the following water supplies:

  • In natural water sources such as rivers or lakes
  • In main water supplies
  • In potable or non-potable water systems

Legionnaires’ disease is a potentially deadly form of pneumonia. This means that preventing the build-up of legionella bacteria in water systems is crucial.

The disease is most commonly contracted by breathing in contaminated water vapor droplets from heating, ventilation and air conditioning (HVAC) systems.

What causes legionella in water?

Legionella bacteria thrive in warm, stagnant water with a source of nutrition. Water temperatures between 20-45°C containing an accumulation of lime scale algae or rust provide an ideal condition for this bacteria to grow. 

These impurities feed the bacteria (which then multiplies rapidly, infecting the water supply).

Outbreaks of Legionnaires’ disease often originate from water distribution systems in large buildings such as hospitals, hotels, and schools. This is particularly dangerous as a many people are exposed to the affected water supply at any one time. Anybody can contract Legionnaires’ disease, but young children, elderly people and people with lung or heart problems are most vulnerable.

Detecting legionella in water supplies

A risk assessment should be carried out to determine how likely the water is to harbor Legionella bacteria. This risk assessment will highlight necessary actions.

The table below shows what risk assessors are likely to look at when completing a legionella risk assessment.

Identifying systems contaminated with Legionella
Water system design
A water system with inadequate insulation, oxidized pipes and water systems without lids have a higher risk of contamination.
Infrequent use
Systems which have not been used recently, or not used often, allow water to stagnate. This water becomes a breeding ground for bacteria. Systems should be flushed out and treated before being used.
Water should be stored at a temperature of 60 degrees Celsius and above in hot water systems and below 20 degrees Celsius in cold water systems - temperatures inside this range are likely to be contaminated.
Hot and cold water systems should be drained periodically in order to determine if there are any signs of corrosion or debris.
Water samples should be tested frequently using a Legionella test kit in order to ensure that the bacteria count is sufficient.

How to get rid of legionella in water systems

Affected water sources can be treated in a number of ways:

  • Addressing water temperature – this involves heating the water supply to 60°C and above as the legionella bacteria cannot survive at this temperature.
  • Sterilization – cleaning and disinfecting water pipes and systems will help to dissolve and remove the harmful bacteria.

Legionella in your water supply is treatable, however having a legionella prevention plan is key to counteracting the potentially devastating effects of Legionnaires’ disease.

NCH Chem-Aqua specialists understand that Legionella awareness is key to eliminating risk. Our team of water treatment experts work hard to develop processes that prevent and eradicate Legionella bacteria from industrial water supplies.



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