There are various systems of control required to manage the risks posed by Legionella, and sampling is a key method of determining if the controls you have put in place are effective. There is no specific requirement to test domestic water systems for the presence of Legionella however, sampling must be carried out for evaporative cooling systems and spa pools.
There are a variety of sampling methods available with innovations in recent years producing several rapid test kit options for consumers, as well as the more traditional lab culture methods. Both styles of testing have their benefits and draw backs.
Points to consider when assessing your options with Legionella sampling:
- Any sampling should form part of a rationalised approach to your management. Random and/or isolated sampling provides little real assurance – it is just a point in time result with no context.
- Culture takes time to produce a result (days), while rapid methods (as the name indicates) produce quick results (hours).
- Rapid tests are often very specific to certain types of Legionella and some do not differentiate between live and dead bacteria.
- Rapid testing methods are comparatively easy to use, while culture methods need a laboratory.
- Interpretation of results can be more difficult with rapid methods as they do not always conform to HSE ACoP/guidance.
- Lab culture testing should be carried out in a UKAS accredited laboratory, because the process follows a specified and vetted process.
- Badly taken, handled and process samples, of any type, rarely produce good or accurate results.
- Rapid test kits often have a shelf life, so control is needed for their use – we have seen many “well out of date” dip slide test over the years!
Consider why you are you testing. If you are testing as part of your scheme of management control, you will have an array of other results and factors to help assess your performance, so time may not be such a factor and culture testing with accredited methods will be more reassuring. If you need results fast to eliminate systems quickly for an investigation for example, a rapid test could be the answer.