Under NM drinking water regulations, what is the maximum number of hours allowed between collecting a distribution system sample and analysis for total coliforms?

• A. 30 hours
• B. 12 hours
• C. 24 hours
• D. 48 hours

Answer: (A)

Holding time matters in drinking water testing because the sample must reflect the water as it was at collection. In New Mexico regulations for distributing system total coliform samples, you may have up to 30 hours from collection to analysis, provided the sample is kept properly preserved (typically refrigerated). This limit helps ensure the detected coliforms (if any) represent the water at the time of collection and not changes that can occur during transport or storage. If analysis isn’t completed within 30 hours, the sample is considered invalid and must be recollected and re-tested.