What does drinking water standards specify for safe water regarding testing results?

The standards for safe drinking water, particularly regarding the presence of coliform bacteria, emphasize the importance of limited positive results from testing. Specifically, the correct answer indicates a threshold allowing for only one positive sample within a specified number of total samples analyzed. This control is crucial because the presence of coliform organisms can indicate possible contamination by pathogenic bacteria, which pose health risks.

The regulation typically holds that if a water system tests regularly and finds more than this allowed number of positive samples, it may indicate a failure in the water treatment or distribution system, prompting necessary investigations and remediation efforts to ensure water safety.

In other options, the numbers provided do not align with commonly accepted thresholds used to determine safe drinking water quality. Options mentioning higher numbers inaccurately suggest a looser standard that does not adequately protect public health, highlighting why specific regulations exist to limit contamination and safeguard drinking water supplies.