When must a repeat sample be collected following a TC+ routine sample?

The appropriate timeframe for collecting a repeat sample after obtaining a total coliform (TC+) routine sample is within 24 hours. This requirement is essential for several reasons. First, total coliform bacteria are an indicator of potential contamination and a sign that the water supply may not meet safety standards. Timely follow-up sampling allows for rapid assessment of the water quality, ensuring any potential hazards can be addressed quickly to protect public health.

Collecting the repeat sample within 24 hours helps in making informed decisions about the safety of the water supply and determining the source of contamination, whether it be from the distribution system or environmental sources. Additionally, local and federal regulations often stipulate this 24-hour time frame as a standard practice to ensure regulatory compliance.

Timeframes longer than 24 hours could lead to misleading or outdated information regarding the water's safety status, which is critical for maintaining effective water treatment and public safety protocols.