When calculating hydrostatic pressure in a well, which factor is disregarded?

• A. Atmospheric pressure at the surface
• B. Atmospheric pressure inside the well
• C. Water temperature
• D. Friction losses in the pipe

Answer: (B)

Hydrostatic pressure is determined by the weight of the water column above a point. The pressure inside the air space of the well (the atmospheric pressure in the well) does not add to that water pressure and is typically ignored when you’re calculating the hydrostatic head. In practice, engineers use gauge pressure for these calculations, which excludes atmospheric pressure entirely, so only the water column’s height and density matter.

Water temperature can affect density slightly, so a precise calculation might adjust density accordingly. Friction losses in the pipe are about flow and head loss due to pipework, which are not part of the static hydrostatic pressure calculation.