What is the purpose of an air line in well measurement?

• A. To measure water level
• B. To aerate water
• C. To vent air from the system
• D. To deliver chlorine

Answer: (A)

Using an air line to measure water level relies on transmitting the hydrostatic pressure of the water column down the line to a gauge at the surface. The air-filled line extends from the surface into the well, and as the water level rises or falls, the column height changes the pressure inside the line. That pressure is read at the surface and, using the relation P = ρgh, you can calculate exactly how deep the water surface is below ground. This method lets you determine the static water level and drawdown without lowering measuring devices into the well. It’s not used to aerate water, vent the system, or deliver chlorine; those are separate functions.