Total dynamic head for pumping: The head against which a pump–motor set must work to lift water includes which components under typical design conditions?

Introduction / Context:
Proper pump selection requires calculating the Total Dynamic Head (TDH) against which the pump must operate. TDH aggregates static elevation differences and head losses so that the pump–motor combination delivers the required discharge efficiently and reliably.

Given Data / Assumptions:

• Pumping from a well or sump to a delivery point at higher elevation.
• Water level lowers during pumping (drawdown).
• Water flows through a discharge pipeline with finite length, diameter, and fittings.

Concept / Approach:
TDH typically consists of static head (difference in elevation from pumping water level to discharge point), plus friction losses along pipes and appurtenances, plus minor velocity head at discharge if relevant. Including drawdown ensures the pump can handle worst-case lowered water levels during operation.

Step-by-Step Solution:
Static lift: elevation difference including maximum drawdown.Friction losses: compute using headloss equations and sum fittings losses.Velocity head: v^2 / (2g) at the discharge section if specified by design.Sum components: TDH = static + friction + velocity head.

Verification / Alternative check:
Pump curves are selected by TDH at design flow. Field commissioning confirms operating point close to curve predictions when each head component is correctly included.

Why Other Options Are Wrong:
Any single component alone underestimates the required head; omitting drawdown or friction leads to undersized pumps and poor performance.

Common Pitfalls:

• Using static water level instead of pumping water level; drawdown can be significant.
• Ignoring minor losses (bends, valves) which add up in long pipelines.

Final Answer:
all the above