Water sampling and testing
Legionella testing and water sampling
Laboratory testing tells you what is in your water. We recommend it when there is a reason. We will tell you when there is not.
When sampling makes sense
HSE guidance in HSG274 Part 2 says routine sampling of hot and cold water systems is not usually needed. Sampling is right in particular situations:
- Temperatures cannot be kept in the safe range.
- The system is treated with a biocide instead of temperature.
- Vulnerable people use the water such as in care homes and healthcare.
- There is a suspected or confirmed case of Legionnaires' disease.
- After disinfection or major work to check the system is clear.
Where a building has stored water we often suggest one baseline set of samples. It gives you a starting point for future checks.
How we sample
We take samples from the outlets your risk assessment identifies. They go to a UKAS accredited laboratory near your site for analysis. You get the results with a plain English explanation.
Reading the results
Results are given in colony forming units per litre. HSG274 sets out what to do at each level for hot and cold water systems:
| Legionella count | What it means |
|---|---|
| Under 100 cfu/l | The system is under control. |
| 100 to 1,000 cfu/l | Resample and review the controls. Act if the result is repeated or affects many samples. |
| Over 1,000 cfu/l | Resample and review the risk assessment straight away. Disinfection is likely. |
Questions
Common questions
Is legionella testing a legal requirement?
Not for most hot and cold water systems. The law asks for a risk assessment and controls. Cooling towers and spa pools are different and need routine sampling.
How long do results take?
Legionella cultures take several days to grow in the laboratory. We send your results as soon as they are confirmed.
What if a sample comes back positive?
We explain what the count means and what to do next. That may be a resample or a disinfection. It may also mean a review of your controls.
Find out what your building actually needs
Book a survey and we will give you a fixed quote. You will also get an honest view of what you can safely do in house.
Request a survey