Final answer:
The question does not provide specific details for determining an exact minimum flow rate for line flushing. Typically, line flushing requires achieving turbulent flow.
Step-by-step explanation:
The minimum flow rate for line flushing before sampling is not explicitly provided in the question; however, it typically depends on several factors, including the diameter of the pipe, the viscosity, and temperature of the water. Flushing is essential to clear any stagnant water and debris.
For a water main with a 0.200-m diameter, the flow rate at which turbulence begins to develop, which helps to flush the system effectively, will also depend on additional factors like the Reynolds number and the water temperature. Assuming the temperature is 20 °C.
Which generally requires a Reynolds number exceeding 4000, you would need to calculate flow rate using the given diameter and the properties of water at that temperature. Although an exact flow rate for minimum flushing cannot be derived from the information given.