Well Contractor Exam · Free practical tool

Total dynamic head worksheet

Build head from the pumping water level to the discharge condition. Avoid counting drawdown twice after a pumping level has already been supplied.

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The method

TDH = pumping depth + discharge elevation + discharge gauge pressure/(ρg) + losses.

Before using the result

  • Pumping depth already includes drawdown: do not add drawdown again. Source is an open water surface; discharge velocity-head differences are excluded.

Worked examples

These original training examples illustrate the method for NGWA Certified Well Driller (CWD) General Drilling Examination. Use the matching “Load example” button above to explore a variation; example values are not equipment settings or prescribed criteria.

1. Worked example

Build head from the pumping water level to the discharge condition. Avoid counting drawdown twice after a pumping level has already been supplied.

Pumping water depth below datum
25 m
Discharge elevation above datum
3 m
Required discharge gauge pressure
200 kPa
Pipe/fitting head losses
5 m
Fluid density
1,000 kg/m³
  1. Lift = 25 + 3 = 28 m.
  2. Pressure head = 200000 / (ρg) = 20.394324259558566 m.
  3. TDH = 28 + 20.394324259558566 + 5 m.
  • Vertical lift: 28 m
  • Discharge pressure head: 20.39432 m
  • Total dynamic head: 53.39432 m

2. Comparison example

Compare a different supplied condition using the same method. For Well Contractor Exam, the important check is that the input meaning, units and method assumptions still match the problem.

Pumping water depth below datum
35 m
Discharge elevation above datum
3 m
Required discharge gauge pressure
200 kPa
Pipe/fitting head losses
5 m
Fluid density
1,000 kg/m³
  1. Lift = 35 + 3 = 38 m.
  2. Pressure head = 200000 / (ρg) = 20.394324259558566 m.
  3. TDH = 38 + 20.394324259558566 + 5 m.
  • Vertical lift: 38 m
  • Discharge pressure head: 20.39432 m
  • Total dynamic head: 63.39432 m

Check your understanding

1. Which relationship is used?

TDH = pumping depth + discharge elevation + discharge gauge pressure/(ρg) + losses.

2. Which assumption should you check first?

Pumping depth already includes drawdown: do not add drawdown again. Source is an open water surface; discharge velocity-head differences are excluded.

3. How should you verify a different unit system?

Convert every input to the displayed calculation units first. Equivalent physical inputs must give equivalent results; a unit label alone does not convert a number.

Continue with the matching exam topic

This tool connects to NGWA Certified Well Driller (CWD) General Drilling Examination free practice. Work through a question independently, then use the calculation steps to identify where your method differs. The tool stays free whether or not you choose paid preparation.