Why is sodium thiosulfate added to bottles for collecting water samples from swimming pools?

Sodium thiosulfate is specifically added to water sample bottles intended for the collection of pool water in order to neutralize residual chlorine. Chlorine is commonly used as a disinfectant in swimming pools, and if present in the water sample when testing is conducted, it can interfere with the results, especially if the tests are designed to evaluate microbial content or other water quality parameters.

By incorporating sodium thiosulfate in the sample collection process, residual chlorine is effectively neutralized. This ensures an accurate representation of the water quality without the influence of chlorine, allowing for reliable analysis of microbial populations and overall water safety. The role of sodium thiosulfate is therefore crucial in maintaining the integrity of the sample for subsequent testing and analysis, making the collection results more valid and representative of the pool's true condition.