To Sample, or not to Sample?
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With the exception of high risk processes such as cooling towers and evaporative condensers the issue of whether or not to take either routine samples, or at the point of risk assessment, from standard domestic water systems has been and continues to be a topic of much debate. It is hoped that the upcoming British Standard for risk assessment
will shed some light, or at least some standardisation, on specific requirements though early indications show this may not be the case.
ACOP L8 (Approved Code of Practice for Legionnaire's disease) states that routine water sampling is not a requirement, except in the following circumstances;
1. Where biocides are used and distribution temperatures are reduced
2. Where control levels are not consistently achieved
3. In an outbreak or suspected outbreak scenario
4. In hospital wards with ‘at risk’ patients
Despite this a large number of organisations spend vast amounts of money on water sampling every year and in some instances rely purely on test results with the absence of any other control mechanisms. What we do know is that Legionella are naturally occurring bacteria and in any given building if we look long enough and hard enough, and take enough samples, the bacteria will be found. In addition to this, simply taking a few samples and getting negative results does not mean that water is safe.
All that water sampling will tell us is if there are bacteria there on that day at that point in time, they may subsequently be flushed away with the next use of the outlet, indeed the majority of positive samples relate simply to outlet contamination rather than a systemic problem with the water system. Is it then better to spend time and money managing the conditions suitable for growth rather that testing to see if they are there or not?
Certainly processes deemed to be ‘high risk’ or those that meet the chain of events should be subject to a regular water sampling regime such as paint plants and those domestic systems that have proved problematic in the past. A good example being an elderly care home with old corroded pipework and a history of positive samples, this would certainly meet the criteria of containing ‘at risk’ individuals and possibly not meeting the necessary control levels as often older buildings cannot afford the installation of TMVs (blender valves) at all outlets meaning that temperatures have to be reduced to prevent the creation of a scald risk – surely a case for water sampling?
It remains the case that there are no hard and fast rules precisely when and how often samples should be taken – if in doubt refer to the risk assessment or contact us at www.nemco-utilities.co.uk for assistance.
About the Author
Charles has been working with the various facets of legionnaire's disease for some time now and has a wide expertize on the same. He shares his insights with the readers through his scholarly articles.
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