Water testing, analysis, sampling strategy
Water testing appears to be a simple process of filling a sample bottle, but it can become extremely problematic as the method and process of sample taking can have an important effect on the final sample results.
For instance, there are two types of sampling. Pre-flush and post-flush. A pre-flush is a sample taken before the tap is flushed, and a post-flush is a sample taken after the tap is flushed. Depending on how long the tap is run will determine how far into the system the sample is taken from. This is why all sampling should be undertaken in accordance with BS 7592 as a simple change in how the sample is taken can have a significant impact on the results.
Also, it is important not to mix samples from two taps into a single bottle. This will dilute any positive results. It is also more costly should you have a positive because you will need to take further water samples to identify where the bacteria is present.
The appropriate techniques must be used to ensure the validity of the sample results. These techniques may include:
- Appropriate use of PPE
- Sampler cleanliness
- Cross contamination
- Speed of delivery from time taken to delivery to laboratory