Centrifugal pumps in water supply: Identify the main drawback and related limitations in typical operation.

Introduction / Context:
Centrifugal pumps are widely used for water supply due to simplicity and smooth flow, but designers must recognize operational constraints that affect reliability and energy performance.

Given Data / Assumptions:

• Standard single-stage centrifugal pump, flooded suction not guaranteed.
• Cold water near atmospheric conditions.
• Conventional system curve with varying head.

Concept / Approach:

Because a centrifugal pump cannot self-prime (unless specifically designed), the casing must be filled before startup. Its discharge depends on the intersection of the pump curve and system curve; as head changes, flow changes. For high heads, multi-stage or alternative types are preferred since efficiency of a single-stage unit declines. Suction lift is bounded by atmospheric pressure and NPSH requirements, typically limiting practical suction to ≈6–7 m at sea level.

Step-by-Step Solution:

Verification / Alternative check:

Manufacturer curves and standards confirm performance limitations and priming requirements; field practice often employs flooded suction or foot/check valves.

Why Other Options Are Wrong:

• Each item reflects a genuine limitation; focusing on only one understates real-world considerations.

Common Pitfalls:

• Running unprimed pumps causing seal and impeller damage.
• Oversizing leading to operation far from BEP and higher energy costs.

Final Answer:

All the above.