Free Engineering Tool · NFPA 20 / NFPA 25
Fire Pump Test Curve Plotter
Plot a fire pump’s rated, shop test and field test curves on one chart. Field readings are corrected to rated speed with the affinity laws, checked against the NFPA 20 churn and 150 percent limits, and summarized in a report you can print to PDF or export to Word.
- Based on NFPA 20 / NFPA 25
- Free, runs in your browser; your inputs stay on your device
- Screening tool, not reviewed or sealed by a licensed engineer
- Last updated October 2026
Screening tool, not engineering advice. This calculator estimates results with simplified published methods. It has not been reviewed or sealed by a licensed engineer for your project, and DGA does not warrant that its results are accurate, complete or suitable for any use. Check every result independently and have the licensed professional responsible for your project review it before you rely on it. Use is subject to the Terms of Use.
Pump Nameplate
Rated Curve
| Point | GPM | PSI |
|---|
Acceptance Allowance
Manufacturer's Shop Test Curve
| GPM | PSI |
|---|
Field Test: PLD Disengaged
| GPM | Suct PSI | Disch PSI | RPM | Net PSI | Corr GPM | Corr PSI |
|---|
Field Test: PLD Engaged
| GPM | Suct PSI | Disch PSI | Net PSI |
|---|
Fire Pump Performance Test Report
Performance Assessment & Test Data
About This Tool
Enter the nameplate rating (flow, pressure and speed) and the tool builds the rated curve and checks the two NFPA 20 limits: churn pressure no more than 140 percent of rated pressure, and at least 65 percent of rated pressure at 150 percent of rated flow. The manufacturer’s shop test curve can be entered in psi or feet of head.
Field test points are entered as suction pressure, discharge pressure and speed. Net pressure is corrected to rated speed (flow by the speed ratio, pressure by its square) before it is compared with the rated curve, using an adjustable 5 percent allowance. Pumps with a pressure limiting driver get a separate PLD-engaged curve that is plotted but not graded. Tests can be saved in the browser, exported to JSON, printed as a landscape report or exported to Word.
When to bring in an engineer
Annual flow tests are a contractor task under NFPA 25. A pump that falls below its curve, never met its rating, or shows unstable suction pressure is an engineering question: water supply, suction piping, driver or controller. DGA designs fire pump installations and supports acceptance testing; see the diesel fire pump acceptance test guide.
Frequently Asked Questions
What are the NFPA 20 limits on a fire pump curve?
For a horizontal centrifugal fire pump, churn (shutoff) pressure may not exceed 140 percent of rated pressure, and at 150 percent of rated flow the pump must deliver at least 65 percent of rated pressure. Acceptance testing compares the field curve, corrected to rated speed, with the manufacturer’s certified shop curve.
Why correct field test data to rated speed?
Pump output depends on speed. Diesel drivers and some electric drivers do not run at nameplate speed during a test, so flow is scaled by the speed ratio and pressure by the square of the speed ratio (the affinity laws) before the results are compared with the rated curve.
What is a pressure limiting driver (PLD)?
A pressure limiting driver is a diesel engine control that lowers engine speed to keep discharge pressure below a set limit. Its curve shows how the pump runs with the control active, so it is plotted separately and not graded against the rated curve.
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Engineering aid only, provided as is and without warranty. Results depend on the inputs and on the simplifying assumptions of the method summarized on each tool page, and DGA has not verified them for your application. They do not replace code-required design, testing or review by the licensed engineer responsible for the project. Use of the tools is subject to the Terms of Use.
Related Reading
Articles from DGA Insights on the code and the method behind this calculator.