Legionella Water Testing

Legionella Bacteria & Legionella Water Testing

Legionella bacteria is commonly found in natural water sources such as rivers, ponds and lakes, in low numbers. They can also be found in man-made systems such as:

  • Hot and cold water systems
  • Spa pools
  • Jacuzzis and hot tubs
  • Showers
  • Cooling towers

In temperatures of 20 to 45 degrees Celsius, the bacteria can multiply increasing the risks of Legionnaire’s disease.

Legionnaire’s disease is a potentially fatal type of pneumonia, contracted by inhaling airborne water droplets containing viable Legionella bacteria.

Anyone can develop Legionnaire’s disease but the elderly, smokers, those with cancer, diabetes or chronic respiratory or kidney disease are at more risk.

A legionella sample result can take up to 12 days to receive, as laboratory testing is required. This is due to the culture method deployed, allowing the organism to grow on the inoculated plate. This is the most reliable legionella testing method.

Is legionella water testing required?

The frequency you should carry out a test for Legionella depends on the system you operate and the outcome of your risk assessment. Should the assessment conclude there are no risks, then testing will not be required.

Purpose of legionella water testing

The purpose of a risk assessment is to identify and assess any risks in your water system.

The person undertaking the assessment should understand your water systems and any associated equipment, enabling them to conclude whether the system is likely to create a risk from exposure to Legionella.

Controlling the risks from legionella in your water system

In order to limit the risks from legionella bacteria, you should operate your water systems under conditions that will either prevent or control the risk, such as:

  • Avoid temperatures that favour the propagation of legionella
  • Ensure water cannot stagnate anywhere in the system (keep pipe lengths as short as possible and remove redundant pipe work including dog legs)
  • Keep the system clean and well maintained