The method
Before using the result
- Use actual internal diameter, not a nominal pipe-size label. A calculated velocity is not a pipe-sizing approval.
Worked examples
These original training examples illustrate the method for Journeyman Plumber (JP). Use the matching “Load example” button above to explore a variation; example values are not equipment settings or prescribed criteria.
1. Worked example
Compare the velocity produced by the same flow through different actual internal pipe diameters. Use the calculation as a water-system learning aid rather than a substitute for a demand-sizing method.
- Solve for
- Velocity
- Actual internal diameter
- 50 mm
- Volume flow
- 2 L/s
Supplied comparison internal diameters
| Internal diameter (mm) |
|---|
| 40 |
| 60 |
- Area = π × 0.05² / 4 = 0.001963495408493621 m².
- Q = A × v; flow = 0.002 m³/s.
- Flow: 0.002 m³/s
- Velocity: 1.018592 m/s
2. Comparison example
Compare a different supplied condition using the same method. For Plumber Conquer, the important check is that the input meaning, units and method assumptions still match the problem.
- Solve for
- Velocity
- Actual internal diameter
- 50 mm
- Volume flow
- 3 L/s
Supplied comparison internal diameters
| Internal diameter (mm) |
|---|
| 40 |
| 60 |
- Area = π × 0.05² / 4 = 0.001963495408493621 m².
- Q = A × v; flow = 0.003 m³/s.
- Flow: 0.003 m³/s
- Velocity: 1.527887 m/s
Check your understanding
1. Which relationship is used?
Q = Av; A = πD²/4.
2. Which assumption should you check first?
Use actual internal diameter, not a nominal pipe-size label. A calculated velocity is not a pipe-sizing approval.
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 Journeyman Plumber (JP) 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.