Enter hydrotest data
Formula used in this calculator
Pbase = Pdesign × Test Factor × (Stest / Sdesign)
ΔPhead = ρ × g × h
Plow = Pbase + ΔPhead + Allowance
Phigh = Plow − ΔPhead
σh = (P × D) / (2 × t)
V = (π / 4) × Di2 × L
These equations are useful planning estimates for piping and similar systems. Final test pressure limits must follow the governing project documents, client rules, and applicable construction code.
How to use this calculator
- Enter the design pressure and choose its unit.
- Set the hydrotest factor required by your project or code.
- Provide allowable stresses at design and test temperatures.
- Enter elevation difference from gauge level to the highest point.
- Enter water density, plus any extra allowance for field losses.
- Enter outside diameter, wall thickness, length, and optional inside diameter override.
- Add yield strength if you want hoop stress utilization and margin.
- Press the calculate button to show results, exports, and the Plotly chart above the form.
Example hydrotest planning table
| Case | Design Pressure | Test Factor | Stress Ratio | Elevation | Low-Point Test Pressure | Pipe OD | Wall | Estimated Hoop Stress |
|---|---|---|---|---|---|---|---|---|
| Sample A | 10.00 bar | 1.50 | 1.065 | 12.00 m | 17.13 bar | 168.30 mm | 7.11 mm | 20.26 MPa |
| Sample B | 18.00 bar | 1.50 | 1.030 | 20.00 m | 29.74 bar | 219.10 mm | 8.18 mm | 39.84 MPa |
| Sample C | 145.00 psi | 1.25 | 1.000 | 6.00 m | 188.30 psi | 114.30 mm | 6.02 mm | 17.80 MPa |
Frequently asked questions
1. What is hydrotest pressure?
Hydrotest pressure is the temporary water pressure used to verify system strength and leak tightness. It is usually above design pressure and may need stress-ratio and elevation-head corrections.
2. Why does elevation matter in hydrotesting?
Water creates static head. If the gauge is lower than the high point, the low point sees higher pressure. That difference must be considered to avoid over-pressurizing lower sections.
3. Why compare allowable stress at design and test temperatures?
Material allowable stress may change with temperature. Some methods scale hydrotest pressure by the ratio of allowable stress at test temperature to allowable stress at design temperature.
4. What does hoop stress tell me?
Hoop stress estimates the circumferential stress in the pipe wall during testing. It helps you compare the test condition with material limits and review whether the pressure is reasonable.
5. Should I enter inside diameter manually?
You can leave it blank or zero to auto-calculate from outside diameter and wall thickness. Enter a manual value when lining, corrosion allowance, or actual bore differs from the simple estimate.
6. Does this calculator replace code requirements?
No. It is a planning and checking tool. Final hydrotest pressure, hold time, acceptance criteria, and isolation procedures must follow the governing code, project specification, and approved method statement.
7. What fluid density should I use?
Use the density of the actual test liquid at site conditions. Clean water is often near 1000 kg/m³, but additives, temperature, or special fluids can change the static head.
8. Why export results to CSV or PDF?
Exports help attach calculations to ITP packs, test dossiers, or field records. CSV is useful for logs and spreadsheets, while PDF is convenient for sharing signed planning summaries.