When should you test water for Legionella

Knowing when to test your water for Legionella is a precautionary measure in maintaining a safe and healthy water system. In the UK those people tasked with the management of building water systems are therefore required by health and safety law to deal with the risks related to the growth and spread of Legionella bacteria and one of the ways to do this is by ensuring regular Legionella testing is carried out. The water within the system should be closely monitored to ascertain its state and that calls for predetermined checks to be performed from time to time.

Testing Water Systems for Legionella

Initially, assessments for Legionella risk evaluation were supposed to be conducted every two years or once system changes were applied. However, there have been new developments with regards to the health and safety directions that govern the control and prevention of Legionella. Today, there is more of an emphasis on what risk assessments should be conducted for Legionella and how often this should be done.

There is now a requirement for more regular reviews of water systems and tests for Legionella than has been the case in the past. It is not only a safe procedure but often a legal necessity based on the nature of your water system and the risks it can present. Ideally, some water systems will require tests more often than others. To establish this frequency of testing, a legionella risk assessment procedure is normally conducted to determine the nature of the pipework, plant and equipment, and installed assets such as showers, taps and water tanks. Each of these elements is typically associated with a water system and they come with their own risks and this can be assessed independently during a survey.

Assessments to Determine the Nature of Testing

There are different circumstances that would dictate the need for a new or updated Legionella risk assessment review. You cannot rely on risk assessments that are outdated or where things have changed to the water system, management processes, people or use of the building. There are particular situations where the law requires reviews to be conducted as soon as possible. Here are instances when you will be required to review your water system risk assessment and determine when and how tests for Legionella are to be conducted.

  • When there is population considered to be in a high-risk category, and they are located close to the building or water systems under your control. For instance, it may refer to people with impaired immune systems or the elderly.
  • On occasions when the water system has been renovated with new installations such as pipework and other elements.
  • At times when the water system or building itself is subject to a change of use.
  • Following the release of new laws, guidance or good practice publications with updates on new procedures and recommendations
  • When existing management processes are not proving effective to control the levels of legionella bacteria in the water
  • When there is suspicion about an outbreak of Legionnaires’ disease associated with the water system

When any of these scenarios present themselves, there may be a need for a new or more frequent reviews of the Legionella risk assessment. When there is a suspected outbreak of Legionnaires’ or when the measures of control already in place have not proved effective, microbiological sampling must be conducted to establish the biological risks that exist and that includes tests for the presence of Legionella bacteria, especially L. Pneumophilia levels. The person in charge should seek advice on the most appropriate remedial measures such as a thorough disinfection of the system. Water hygiene specialists can advise on this aspect.

Primarily, Legionella bacteria tests need specialist water analysis companies to provide technical expertise. However, duty holders can evaluate and inspect the water systems for any condition that may sustain the development of Legionella. The risk assessment and management of water systems includes a programme and a number of processes and procedures for conducting regular tests for evidence of such conditions as would support the proliferation of Legionella bacteria.

Legionella Tests in Different Settings

The frequency of tests for Legionella bacteria must be conducted based on the water system, the elements in it and the risks involved. It should also be informed by the risk assessment and control measures defined within that particular assessment. Temperature control and regular monitoring of the hot and cold water temperatures achieved, mainly conducted on a monthly basis is considered an effective method to manage the proliferation of Legionella. Temperatures between 20°C and 45°C provide the right conditions for the growth of Legionella bacteria and so should be avoided. Optimum Legionella growth occurs at 37°C. With knowledge about these temperature conditions in your water system, you can determine what measures to take to control these temperatures: either to keep them lower than 20°C or higher than 45°C depending on each of the elements in the water system. In the UK the requirement is to keep the cold water below 20°C, and the hot water above 55°C.

Tests for Legionella bacteria should be conducted more often than has been the case in the past based on a number of factors and occasions as highlighted in here. These test results need to be recorded for historical reference in order to closely track the progress and how effective the current control measures are. Therefore, water tests should be conducted as often as any these scenarios arise.