The required pumping time before taking a sample for physical and chemical analysis is 36 hours.

The required pumping time before taking a sample for physical and chemical analysis is 36 hours.

• A. 24 hours
• B. 48 hours
• C. 36 hours
• D. 60 hours

Answer: (C)

Purge enough water so the sample represents the source water, not the water that’s been sitting in the well or piping. The 36-hour pumping time is the prescribed duration that ensures stagnation effects—temperature shifts, dissolved gases, pH and conductivity changes—don’t bias the physical and chemical analysis. In practice you’d watch for stabilization of field parameters, but for this test the standard target is 36 hours to ensure a representative sample.

Purge enough water so the sample represents the source water, not the water that’s been sitting in the well or piping. The 36-hour pumping time is the prescribed duration that ensures stagnation effects—temperature shifts, dissolved gases, pH and conductivity changes—don’t bias the physical and chemical analysis. In practice you’d watch for stabilization of field parameters, but for this test the standard target is 36 hours to ensure a representative sample.