What action should be taken first when re-sampling after a failed micro test?

When re-sampling after a failed microbiological test, the first action to be taken is to resample at the previous test site. This approach is essential for pinpointing the specific location where contamination may have occurred. By resampling at the same site, it allows for a direct comparison with the initial test results and helps identify if the problem was isolated or if there might be a broader issue within the system.

Testing in the same location is critical because it follows established protocols aimed at ensuring that the source of contamination can be accurately tracked and addressed. It allows operators to determine if the initial result was due to an anomaly or if contamination is persistent, which is vital for maintaining public health and safety.

If sampling were to occur at different locations throughout the system or if there was a delay in taking action, it could lead to confusion about the integrity of the water supply or misidentify the source of the contamination. Immediate and specific action upon identifying a failed test is key in water quality management.