When selecting a screen for a groundwater monitor well, which factor is essential?

• A. Slot size matched to filter pack material
• B. Screen color
• C. Screen length
• D. Casing material color

Answer: (A)

The important idea is that the screen openings must be sized to the surrounding filter pack material. The screen sits inside a filter pack (gravel and/or sand) that acts to keep sediments from entering the well while letting water through. If the slot size is too large relative to the filter pack, fine sediments can pass through the pack and into the well, causing clogging and contaminated samples. If the slots are too small, the screen can clog quickly and resist water flow, reducing pump efficiency. Matching the slot size to the grain size of the filter pack ensures water can enter readily while keeping the filter media in place, which is essential for reliable monitoring and long-term well performance. The other factors—screen color, casing color, or even screen length—do not affect this hydraulic relationship in the same fundamental way.