Before taking a sample for bacteriological testing, how must a pipeline be prepared?

To accurately determine the presence of bacteria in a water sample, proper preparation of the pipeline is essential. Flushing the pipeline of chlorinated water is crucial because chlorine can inhibit bacterial growth, leading to false-negative results in testing. If the sample taken contains chlorine, the bacteria being tested may not be able to thrive or multiply, which would misrepresent the actual microbial quality of the water. Therefore, ensuring that the pipeline is flushed allows for a more reliable sample that reflects the true microbial presence in the water without the interference of disinfectants like chlorine.

In contrast, draining the pipeline entirely could lead to a loss of residual water quality data. Filling the pipeline with chlorinated water would further complicate testing, as it would mask any bacterial growth that may be present. Heating the water to a specific temperature is not standard procedure for preparing water samples and does not align with testing protocols for bacteriological analysis.