If the energy grade line is rising along a pipe with no external energy addition, what does this imply about losses and elevations?

• A. EGL always rises in a passive system
• B. Elevation gains or pumps offset losses; in purely passive system EGL cannot rise without energy addition.
• C. EGL depends only on pressure, not energy
• D. EGL drops with any loss

Answer: (B)

The Energy Grade Line represents the total energy per unit weight along the flow, combining pressure energy, elevation energy, and velocity energy. In a pipe with friction losses and no external energy added (no pump or other energy source), those losses reduce the total energy as you move downstream, so the EGL generally trends downward.

If you ever see the EGL rise along a section, it means energy is being supplied or energy is being gained from elevation. Elevation gain adds potential energy (z) to the line, and a pump adds energy to the system. In a purely passive system with no energy input, the EGL cannot rise; to offset the losses, either the path must gain elevation or an external energy source must be present. That’s why the correct statement is that elevation gains or pumps offset losses; in a purely passive system the EGL cannot rise without energy addition.