For conductivity sampling, which statement is correct?

For conductivity sampling, which statement is correct?

• A. 50 mL, an unpreserved, at the entry point to the distribution system
• B. 100 mL, a preserved, at the entry point to the distribution system
• C. 50 mL, an unpreserved, from the furthest points in the distribution system
• D. 100 mL, an unpreserved, from the furthest points in the distribution system

Answer: (A)

Conductivity is a quick measure of the total dissolved ions in water and is reliable without any preservation for short times. To get a representative reading of what's leaving the treatment process, you sample at the entry point to the distribution system—the water entering the network—so the result reflects the plant’s output rather than what has spent time in pipes. A modest volume, 50 mL, is enough for a conductivity measurement and keeps handling simple. Sampling from farthest points in the distribution system can give readings influenced by residence time, pipe interactions, and potential buildup, which don’t represent the treatment plant’s performance. Preserving the sample isn’t needed and could introduce extra ions, skewing the reading.

Conductivity is a quick measure of the total dissolved ions in water and is reliable without any preservation for short times. To get a representative reading of what's leaving the treatment process, you sample at the entry point to the distribution system—the water entering the network—so the result reflects the plant’s output rather than what has spent time in pipes. A modest volume, 50 mL, is enough for a conductivity measurement and keeps handling simple. Sampling from farthest points in the distribution system can give readings influenced by residence time, pipe interactions, and potential buildup, which don’t represent the treatment plant’s performance. Preserving the sample isn’t needed and could introduce extra ions, skewing the reading.