The line joining the heights to which water would rise in vertical piezometer tubes fitted at different sections of a pressurized conduit is called what?

Introduction / Context:
Visualizing energy distribution in pressurized pipe systems uses two companion curves: the Hydraulic Grade Line (HGL) and the Energy Grade Line (EGL). Piezometric tubes (or pressure taps plus elevation) reveal the HGL directly as water levels at points along a pipeline.

Given Data / Assumptions:

• Pressurized, steady, incompressible flow in a closed conduit.
• Neglect air entrainment; tubes measure static head (p/γ + z).
• No pump/turbine stations between measurement points.

Concept / Approach:

The height to which water rises in a piezometer equals the piezometric head (pressure head + elevation head). The locus of these heights is known as the Hydraulic Grade Line (also called piezometric line or pressure grade line). “Hydraulic gradient” strictly refers to the slope of the HGL, not the line itself.

Step-by-Step Solution:

Verification / Alternative check:

In a uniform pipe with friction, HGL slopes downward in the flow direction; pumps cause a jump up, while turbines cause a drop, aligning with standard energy accounting.

Why Other Options Are Wrong:

(a) “Hydraulic gradient” names the slope, not the line. (e) “All of the above” would include (a), which is not a name for the line itself in strict usage; hence the best single term is HGL (d). (b) and (c) are synonyms for HGL, but only one option should be chosen; the standard engineering term is the Hydraulic Grade Line.

Common Pitfalls:

Confusing HGL with EGL; the difference is the velocity head.

Final Answer:

Hydraulic grade line