Before taking a sample, how long should you ideally flush the line?

Flushing the line before taking a sample is a critical step to ensure accuracy and reliability in water quality testing. The reason the recommended duration is typically 3-5 minutes is to allow for the stagnant water in the service line to be cleared out. This stagnant water can contain contaminants that do not represent the overall water quality, as it has likely been sitting in the pipes and might include materials from the pipe's interior or even contaminants from previous use.

Flushing for 3-5 minutes helps to ensure that you are getting a sample of fresh water that has not been influenced by these conditions. This duration strikes a balance, providing enough time to clear the old water while avoiding excessive waste of water and time. Longer flushing periods could be unnecessary in many cases, as most systems will have already ensured that lines are adequately flushed, making 3-5 minutes a widely accepted standard in the industry for routine sampling protocols.