What is the correct procedure for collecting a tap water sample for bacteriological analysis?

The correct procedure for collecting a tap water sample for bacteriological analysis involves opening the tap for 2-3 minutes while holding the bottle by the base. This method ensures that the sample accurately represents the water quality and minimizes the risk of contamination.

Holding the bottle by the base is important because it reduces the chance of introducing contaminants from the hands or other surfaces into the sample. This is critical in microbiological testing where even minute contamination can skew results. Additionally, letting the tap run for 2-3 minutes before collecting the sample achieves a steady flow of water, flushing out any stagnant water that may have been sitting in the pipes, which could contain higher levels of contaminants that aren't representative of the water quality.

In contrast, holding the bottle by the neck or simply opening the tap without allowing it to run sufficiently could lead to contamination or an unrepresentative sample, which would compromise the accuracy of the bacteriological analysis.