When collecting water samples, how many identical glass vials must be used?

Using two identical glass vials for water sampling is critical to ensure accuracy and reliability in testing. Having a second vial provides a backup sample in case the first vial is compromised or if there are any issues during analysis. It allows for the opportunity to verify results and conduct tests on both samples, ensuring that findings are consistent. This practice is especially important in environmental monitoring and compliance with regulations, as it helps mitigate the risk of errors that could arise from a single sample collection. The use of identical vials also helps control for any variability in sample containers that might affect the outcome of the testing.