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Legionella Testing & Analysis

Legionella Testing & Analysis


Water sampling & microbiological analysis is an important feature of any control scheme. Water testing is the only way to determine whether Legionella is present in a water system. Because of this, and because of the risks of Legionella exposure, it’s vital that water systems are regularly tested for the bacteria.

A Legionella Risk Assessment will assist in advising areas that need periodic water sampling to test for the presence of Legionella or to show that adequate control is being achieved.

Celtic Water Solutions can advise as to the frequency of sampling, the location and/or the type of analysis required. Depending on the results we can then offer advice as to the necessary action required.

Analysis of water samples for legionella is performed in INAB-accredited laboratories with the current ISO standard methods for the detection and enumeration of legionella included within the scope of accreditation.

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When is Legionella testing required?

Legionella testing must be carried out by a competent person(s) who has had adequate training to identify the conditions that encourage legionella proliferation and when a Legionella Risk Assessment may be required.

Microbiological monitoring of domestic hot and cold water supplied from the mains is not usually required unless the risk assessment or monitoring indicates there is a problem.

It is recommended to test for legionella bacteria when:

  • The limits of a control regime, eg temperature or disinfectant concentrations, are not being consistently achieved.
  • There is a highly vulnerable group of people present on the premises: schools, care homes, hospitals.
  • A water system is suspected or identified in a case or outbreak of legionellosis
  • A water system is being treated with biocides and water is stored or distributed at lower temperatures

In high-risk properties such as hospitals and health care premises, taking samples is a requirement.

How should water sampling be done?

What seems to be a simple process of filling a sample bottle can turn into a major issue as the method and process of sampling can have a substantial effect on the final result obtained.

Where monitoring for Legionella is considered appropriate in hot and cold water systems, sampling should be carried out in accordance with BS7592 “Sampling for Legionella organisms in water and related materials.”

The complexity of the system will need to be taken into account to determine the appropriate number of samples to be taken. To ensure the sample is representative of the water flowing around the system and not just of the area downstream of the fitting, samples should be taken from separate hot and cold outlets rather than through mixer taps or outlets downstream of TMVs or showers.

Whenever possible, samples should be taken from locations considered most likely to contain the highest numbers of legionellae.

Locations for Legionella samples in cold water systems

  • From the point of entry of the mains or nearest outlet to the point of entry into the building
  • Cold water storage tanks
  • From nearest & furthest outlets (Sentinel points) on each branch of the system

Locations for taking Legionella samples in hot water systems

  • From the nearest outlet to the calorifier
  • From the base of the calorifier
  • From the nearest & furthest outlets (sentinel points) on each branch of the system for single-pipe systems
  • From nearest & furthest outlets (sentinel points) on each loop of a circulating system

Samples should be clearly labelled with their source location and if collected pre or post flushing.

Why Choose Celtic Water Solutions?

Celtic Water Solutions offers a comprehensive range of microbiological and chemical testing services for micro-organisms such as Legionella, E. coli, TVC, Coliforms, and Pseudomonas.

Our water quality analysis solutions have been developed to accurately identify whether your water systems meet the safety and quality standards set by the HSE for permitted levels of Legionella bacteria in water.

We use an independent INAB accredited laboratory for our testing to ensure that results are impartial. Once the laboratory analysis is complete, we will send you a full report with results and our recommendations of what the results mean for you and your responsibilities towards the people that come into contact with your water systems.

Speak to an Expert

For further information on legionella testing & water sampling, feel free to contact our team.

Call 093 60705

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Galway Road, Tuam
Co. Galway
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