A legionella risk assessment looks at your water system and identifies where bacteria could grow. Legionella sampling tests the water to see whether they are actually there. The risk assessment comes first, and it tells you whether and how often to sample.
What a legionella risk assessment does
- Surveys the whole hot and cold water system.
- Finds the conditions legionella needs: water between 20°C and 45°C, stagnation, sediment and spray.
- Considers who uses the building and how vulnerable they are.
- Produces a written scheme of control with tasks, owners and frequencies.
Employers are asked to carry out a written risk assessment, record the findings and review it. National guidelines recommend a review at least once a year.
What legionella sampling does
- Takes water from chosen points in the system.
- Has it cultured in a laboratory.
- Reports whether legionella is present and at what level.
A sample is a snapshot of one outlet on one day. It confirms whether your controls are working, but it cannot tell you why a problem exists or where the next one will appear.
Side by side
| Risk assessment | Sampling | |
|---|---|---|
| Question it answers | Could legionella grow here? | Is legionella here now? |
| Covers | The whole system | The points sampled |
| Output | Control scheme and action plan | Laboratory results |
| How often | Review at least yearly | As the risk assessment sets out |
When you need both
- Healthcare settings, including nursing homes, where national guidelines recommend sampling at least twice a year.
- Systems where temperatures are hard to control.
- Buildings reopening after a closure.
- After a positive result, to confirm the fix worked.
Which should you book first?
The risk assessment. Sampling without one tells you a result but not what to do about it.
Safer Solutions provides both legionella risk assessments and legionella sampling, with samples analysed by an independent accredited laboratory. Call 086 275 9728, email info@safersolutions.ie or request a quote.