What is the sampling procedure for a positive distribution sample?

In a situation where a positive distribution sample is identified, it's crucial to conduct a thorough follow-up sampling procedure to evaluate the extent of contamination and identify the source. The recommended approach includes gathering samples from multiple points within the distribution system to ensure that results accurately reflect the quality of water being distributed to consumers.

The procedure that involves taking one sample at the original tap, one sample five connections down, and another sample five connections beyond that is comprehensive. This approach helps in identifying if the contamination is localized to a specific area or if it is present further along in the distribution system.

By sampling at the original tap, you're assessing the water quality at the point of use; by sampling five connections down, you can determine whether the contamination is persisting as the water travels through the system; and a further sample five connections down helps in understanding the spread of any potential contaminants. This method provides a broader picture of the water quality throughout the distribution system, which is essential in determining appropriate remediation actions.

Other options are less effective because they do not encompass the same level of thoroughness and may miss areas where contamination could also be present. Thus, the comprehensive nature of the selected sampling procedure is well justified in the context of ensuring safe drinking water.