Calculation sequence
Step-by-step method
- Confirm the calculation boundary, units, and source of every input.
- Apply the displayed equation to the entered values.
- Review the result against governing criteria and documented uncertainty.
PlumbingAdvancedCompressed Air
Compressed-Air Pressure-Decay Leak Calculator
Estimate ideal standard-air leak rate from isolated volume, gauge-pressure decay, atmosphere, and elapsed time.
Why it matters: A transparent formula keeps the user-entered hydraulic, gas, or storage basis available for technical review.
Calculated result
Engineering evaluation
Ideal standard-air leak rate (Q_L)34.014 scfm
Engineering interpretation
The isolated-system pressure decay corresponds to 34.01361 scfm under the ideal model.
Important limitations
- Ideal isothermal decay screen only. Stabilization, temperature drift, connected volume, instrument accuracy, valve leakage, pressure basis, and test duration require documented control.
Engineering knowledge center
Understand the calculation—not just the answer
Governing relationships
Q_L=V(P_1−P_2)/(P_atm t)
Current substitution
Q_L=500×(100−90)/(14.7×10)=34.01361.
Equation legend
Inputs and calculated quantities
- V
- Isolated system volume — ft³ or m³
- P_1
- Initial gauge pressure — psig or kPag
- P_2
- Final gauge pressure — psig or kPag
- P_atm
- Atmospheric pressure — psi or kPa
- t
- Pressure-decay duration — min
- Q_L
- Ideal standard-air leak rate — scfm
Applications
How this calculation is used
Building design
Screen a documented system relationship without embedding a protected design table.
Construction
Check submittal and field values using the same visible inputs.
Commissioning
Reconcile measured and scheduled conditions before professional disposition.
Quality controls
Assumptions and limitations
Assumptions
- Inputs describe one documented system boundary and compatible operating condition.
- All values use the displayed symbols and one consistent unit system.
Limitations
- This screen does not establish code compliance, final design, equipment selection, or acceptance.
- Adopted codes, local criteria, manufacturer data, uncertainty, and professional judgment remain controlling.
Field use
Verification procedure
- Identify the calculation boundary and source of each input.
- Record representative values with compatible pressure, temperature, flow, and time bases.
- Review the result against the adopted criteria, manufacturer data, and uncertainty.
Common engineering mistakes
- Mixing standard and actual gas volumes or gauge and absolute pressures.
- Treating an arithmetic screen as a code-sizing table or hidden acceptance criterion.
Technical basis
References and source standards
- International Plumbing CodeAdopted edition and local amendments govern; protected sizing tables are not reproduced.
- American Society of Plumbing EngineersPlumbing engineering-method context; verify licensed references and project criteria.
- NIST SI and Unit GuidanceUnit and dimensional-conversion basis.
Engineering calculation disclaimer
These engineering tools are provided for educational, preliminary evaluation, field verification, and commissioning support. Results depend on the accuracy of user-entered information and the assumptions stated for each calculation. Every colored status and comparison is a screening indicator only; project criteria, contract requirements, applicable codes, manufacturer instructions, measurement uncertainty, and authorized engineering judgment govern. The tools do not replace project-specific engineering analysis or the judgment of a licensed professional engineer.
Read the full use and limitation statement