Altitude is best defined as:

• A. Term used to describe either pressure loss or pressure gain
• B. Position of an object above or below sea level
• C. Center line of the pump or the bottom of a static water supply source above or below ground level
• D. Part of the total pressure lost while forcing water through fire hose

Answer: (B)

Altitude is the vertical position of an object relative to sea level. In firefighting hydraulics, this matters because hydrostatic pressure in a water column changes with elevation—the higher you are, the lower the pressure at a given reference point, and vice versa. For example, moving water higher by one foot reduces pressure by about 0.433 psi. This concept describes where something sits in space, not a feature of the pump setup, a portion of friction losses, or a general term for pressure gain or loss. So altitude is defined as the position of an object above or below sea level.