The method
Before using the result
- Use a representative steady-flow collection; container and timing uncertainty are not estimated.
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
Calculate a field collection flow from a known container volume and representative fill time. Make the minutes-to-seconds conversion visible.
- Collected volume
- 20 L
- Elapsed time
- 1 min
- Q = 0.02 / 60 m³/s.
- Measured flow: 0.0003333333 m³/s
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.
- Collected volume
- 40 L
- Elapsed time
- 1 min
- Q = 0.04 / 60 m³/s.
- Measured flow: 0.0006666667 m³/s
Check your understanding
1. Which relationship is used?
Flow = collected volume / elapsed time.
2. Which assumption should you check first?
Use a representative steady-flow collection; container and timing uncertainty are not estimated.
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.