How long should you flush the line before taking a sample?

Flushing the line before taking a water sample is an essential step to ensure that the sample accurately reflects the water quality of the distribution system rather than any stagnant water that might have accumulated in the pipes. Flushing helps to clear out any sediments, biofilms, or contaminants that may have settled.

The recommended duration of 3 to 5 minutes is generally appropriate because it allows enough time for the previous water to be flushed out of the sample tap and for fresh water from the supply line to reach it. This timeframe balances the need for adequate flushing while avoiding excessive waste of water and ensuring that the sample collected is representative of the system's current conditions.

Choosing a more extended period, such as 5 to 10 minutes or longer, could potentially lead to unnecessary water wastage without significantly enhancing the quality of the sample. Conversely, a shorter flush period, such as 1 to 2 minutes, may not adequately clear the line, risking the collection of a sample that does not truly reflect the water quality in the system being tested.