What percentage of positive bacteriological samples can be allowed before a system is flagged?

In water quality management, when evaluating bacteriological sampling results, a system can be flagged if the percentage of positive samples exceeds a certain threshold. For most water systems, a 5% threshold is commonly recognized. This means that if more than 5% of the total bacteriological samples collected during a specific time frame yield positive results for coliform bacteria (or other pathogens), it may indicate a potential contamination issue within the water supply.

This threshold serves as a key parameter for maintaining water safety and public health, triggering further investigation and possibly corrective actions. Keeping the percentage of positive samples at or below 5% is crucial for ensuring that water quality standards are met and that the water supplied to consumers remains safe for use.