Within how many hours must repeat samples be collected after a total coliform positive test?

The correct timeframe for collecting repeat samples after a total coliform positive test is 24 hours. This requirement is based on the need to quickly assess the risk of microbial contamination and ensure that water quality is maintained. Total coliforms can indicate the presence of potentially harmful pathogens, so the timely collection of repeat samples is crucial for protecting public health.

Collecting these samples within 24 hours allows water systems to respond promptly to any contamination that could pose a risk to consumers. If issues are detected, swift action can be taken to rectify the situation, including possible disinfection processes or other corrective measures. This standard is in line with regulatory guidelines established by the Environmental Protection Agency (EPA) and state water quality programs to ensure safe drinking water.

The options for other timeframes, such as 12 hours, 36 hours, or 48 hours, do not align with the best practices and regulatory standards in the industry, as they would potentially delay the response to contamination risks.