Statements about pressure conduits and hydraulic grade line (HGL) Pick the correct statement regarding pressure conduits used in water supply.

Introduction / Context:
Pressure conduits convey water under pressure supplied by pumps or upstream head. Their hydraulics differ from gravity sewers that operate partly full with a free surface.

Given Data / Assumptions:

• Closed, pressurized piping system.
• Steady-state conditions unless otherwise stated.

Concept / Approach:
In pressure flow, the pipe is normally flowing full, with piezometric head above or below the crown. The hydraulic gradient line (HGL) represents piezometric head and generally does not coincide with the invert; it can be above the pipe crown. Pressure pipes can be laid on any grade as pressure (not slope) drives flow.

Step-by-Step Solution:

Verification / Alternative check:
Distribution mains in cities run full regardless of local terrain undulations, provided required pressure is maintained.

Why Other Options Are Wrong:

• (b) Pressure pipes are not limited to down grades; pumps/head control flow.
• (c) HGL ≠ invert in pressurized systems.
• (e) Contradicts basic pressure-flow design.
• (d) is false because (a) is correct.

Common Pitfalls:
Confusing gravity sewers (partly full, free surface) with pressure mains (full, pressurized).

Final Answer:
Pressure conduits are permitted to run full under pressure.