When Should Water Be Tested for Legionella Bacteria?
Are you wondering if you are required by law to test your hot and cold water systems for legionella bacteria? Maybe you already know that your business doesn’t legally require it unless there is a specific need for legionella testing. In that case, how can you tell if a need exists, how often you should test and what should you do?
Legionella testing guidance from the HSE
The Health and Safety Executive (HSE) has indicated several situations whereby legionella testing should be done and these include:
- Where the regime in place to treat a hot and cold water system is suspected to be inefficient
- Where ideal temperatures are not always obtained – hot water should be kept hot, and cold water cold
- Where there is doubt over concentrations of disinfectant in the system that could indicate a lack of control
- Where the situation is deemed high-risk for some other reason
How often should my water systems be tested for legionella?
If there is doubt over the findings of the legionella risk assessment or the prevention procedures currently in place are not working correctly, more regular weekly legionella testing should be undertaken until such time safe tests are obtained consistently over a period of time. At this point, monthly testing may then be more prudent, providing the results back this up.
The HSE’s HSG274 (Part 1) also calls for regular testing of cooling towers because of their higher risk. The make-up water and cooling tower water needs to be tested for both microbial activity and legionella bacteria.
Cooling towers should be tested for legionella at a minimum three month intervals unless there are problems, when more regular testing may be needed until things are resolved.
Identifying legionella sampling points
Water samples should also be taken in several locations each time the water system is tested for legionella. It is worth noting that a variety of water samples taken from various taps and other outlets may not be sufficient to get a completely accurate picture of the condition of the water system. It is possible such tests may show Legionella within safe limits, whereas tests performed in water tanks (hot or cold) may show very different results. Consideration should be given to areas of higher risk, especially where water temperatures drop-out of specification, where stagnant water may be sitting in pipes or tanks, as well as that which regularly flows through the system.
Once the appropriate water testing points have been identified for a specific system, it is prudent to make a note of them so the same points are tested each time. This will form part of the regular checks required to make sure your business adheres to the health and safety laws regarding water systems and the control of legionella bacteria.
Is it best to enlist the aid of experts to handle your water testing?
The HSE expect that any testing for legionella should be done in a UKAS accredited laboratory and an experienced, competent person engaged to interpret the results of the tests. You will need to do this, to make sure every aspect of the law is covered and your own water system is safe. However, if you wish to undertake the water sampling process yourself, appropriate training may be very useful.
In any event, taking the right approach to legionella testing is vital to ensure you are knowledgeable about the safety of your own systems.
Further information, advice and support
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