When collecting a total coliform sample, what is considered good practice regarding the sample cap?

In the context of collecting a total coliform sample, holding the cap with the threads down is considered good practice because it minimizes the risk of contamination. By positioning the cap this way, you prevent any airborne contaminants or other contaminants from settling on the inside of the cap, which could compromise the integrity of the sample. This step is crucial in ensuring that the sample accurately reflects the water's quality without interference from extraneous sources of bacteria or other pathogens.

Good sampling practices are essential to obtain reliable and valid results, especially for tests like total coliform, which can indicate potential issues with water quality and safety. Ensuring that the sample collection process is as sterile as possible is critical in this regard. Other practices, such as touching the inside of the cap or rinsing it with sample water, could introduce contaminants, while leaving the cap open until use exposes it to various sources of pollution, all of which can undermine the sampling process.