How long should a new tank be disinfected before a water sample is collected for coliform analysis?

When disinfecting a new tank prior to collecting a water sample for coliform analysis, the recommended duration for maintaining disinfection is typically 24 hours. This time frame allows sufficient contact between the disinfectant and any potential contaminants within the tank, ensuring effective microbial kill and reducing interference in the subsequent water quality testing.

The significance of this 24-hour period lies in its balance between allowing enough time for the disinfectant to act thoroughly and ensuring that the water quality does not diminish due to prolonged chlorination or other disinfection processes. After this period, the residual disinfectant can be measured, and water samples can be taken for analysis without the altered results that could arise from insufficient or excessive disinfectant presence.

Shorter or longer disinfection times may not achieve optimal disinfection or may lead to overly high levels of residual disinfectant influencing the water quality results, hence the importance of adhering to the 24-hour guideline.