Legionella testing

T he LCA requires its members to possess set up management procedures and appropriately competent staff, that provide them the ability of giving an answer to positive legionella results appropriately. Positive legionella results following sampling are one area where it’s possible to misinterpret this is and end up getting what could at best be inappropriate expense and at worst, a dangerous situation and risk alive.


Interpretation of results starts with the right sample plan. Samples could be taken post or pre flush sufficient reason for or without disinfection of the outlet. Selecting location, kind of method and sample of analysis chosen forms area of the sample plan.

The initial priority ought to be to consider measures to get rid of or decrease the risk before designing monitoring measures. Where it really is impossible or not reasonably practicable to lessen the risk and the chance assessment recommends monitoring for the current presence of legionella by sampling, there are always a true number of things to consider in an example plan; including:

How often should samples be studied?


Positive legionella results occur in around 10-20 % of laboratory water samples, which take 10 days to perform and may have a further two days to verify with traditional confirmation techniques. The laboratory will send a confident notification after the result is confirmed normally.

The LCA would expect that any registered member could have an operation to notify their client, log the total result, track actions, note resolution and close out a confident legionella result.

The effect ought to be notified to litigant at the initial opportunity, which includes interim excellent results. HTM0401 Part B gives advice on how best to interpret positive legionella results in healthcare settings. For other settings the overall principles will be the same, however the susceptibility of the populace may very well be lower.

The interpretation of sample results will observe directly from the well-designed sample plan. An example is really a small part made to represent a more substantial population. In cases like this you’ve selected small volumes of water to represent the chance in the water system all together. When addressing issues, you need to think about the whole system rather than the sample locations if the outcomes indicate widespread contamination just.


An LCA Member’s procedure should detail how they tell their client the info and how they reach the advice they provide. This process should then be followed used and at audit the LCA will be prepared to see an audit trail for every positive result.

For legionella to cultivate there has to be suitable conditions and you will see a real cause for these conditions. Actions following positive samples must address the primary cause instead of just the symptom. Common factors include:

  • Stagnation, areas being less used than previously thought
  • Thermal gain/loss, meaning systems normally reside at growth temperature despite running below 20 degrees after two minutes or above 50 degrees within about a minute
  • Stagnation because of failed HWS circulation
  • Unknown deadlegs
  • Materials or contamination in the machine that support growth

Reviewing the assessment of the chance and addressing whatever is available should be the primary recommendation but unless very easy and straightforward to attain, there must be interim recommendations also.

Recommended actions ought to be appropriate for the outcomes. This is often a difficult balance to strike if the total results indicate limited localised issues, take limited localised action, if results indicate more widespread issues, take system level actions.


The effect ought to be logged on systems as a non-conformance like any lack of control non-conformance. Your interpretation, recommended actions and the reason why behind these ought to be logged and recorded within the process also.


After the result has been logged in something the consequent actions have to be tracked and auditable. If actions are needed by you or your customer then ensure they are completed and recorded in your logging process.


After the real cause has been identified and resolved this step ought to be noted on a LCA’s member’s log and the positive result closed out. Oftentimes it is normal to handle follow-up sampling after remedial action to verify success.


Sampling for legionella is definitely an important area of the tabs on control measures in a written scheme and competent interpretation of excellent results is vital. Appropriate planning, interpretation and technique is key to ensure the info obtained by sampling is valid and useful. The LCA requires members to possess set up management procedures that detail how samples are planned, completed, non-conformances dealt and logged with and actions closed out including communication making use of their clients.