Boiler Feed Pump Calculator
Estimate the required boiler feed pump capacity in GPM from the boiler's steam output and a standard safety factor.
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This is the recommended minimum feed pump capacity in gallons per minute. Pumps are typically selected with some margin above this calculated value.
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How Boiler Feed Pump Sizing Works
Boiler feed pump capacity is sized around the boiler's steaming rate, feedwater conditions, and required discharge pressure to reliably deliver water against boiler operating pressure.
How to Calculate Boiler Feed Pump Requirements
The calculator above works through the specific flow rate, head, and horsepower relationships for your entered boiler parameters — see the calculator for your exact figures, since results depend heavily on your specific boiler's operating conditions.
What Affects Boiler Feed Pump Sizing?
Steaming rate (how much steam the boiler produces, which the feedwater must match), boiler operating pressure (the pump must overcome this to deliver water), and a safety margin above minimum required capacity to handle load swings.
Common Boiler Feed Pump Sizing Mistakes
Sizing exactly to calculated minimum flow with no margin for load swings or future capacity needs. Not accounting for feedwater temperature, which affects pump NPSH (net positive suction head) requirements and cavitation risk. Ignoring total dynamic head (including both boiler pressure and piping losses) when selecting pump horsepower.
How to Use This Calculator
Enter the boiler's maximum continuous steam output in lbs/hr and a safety factor (1.5, i.e. 150% of steam output, is a common industry practice default).
Formula & Methodology
Feed pump capacity (GPM) = (Steam Output in lbs/hr × Safety Factor) / (8.34 lbs/gal × 60 min/hr), converting mass flow of steam to an equivalent volumetric feedwater flow rate.
Example: 10,000 lb/hr boiler, 1.5x safety factor
(10,000 × 1.5) / (8.34 × 60) ≈ 30.0 GPM.
This is a standard sizing approximation. Actual feed pump selection should also account for boiler pressure, feedwater temperature, and the specific pump curve — consult a boiler engineer for final equipment selection.
For preliminary estimation only. Boiler feed pump sizing affects safe boiler operation — final selection should be verified by a qualified boiler engineer.
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Frequently Asked Questions
- How do you size a boiler feed pump?
- Feed pump capacity is typically sized as a multiple (commonly 1.5x, or 150%) of the boiler's maximum continuous steam output, converted from lbs/hr to GPM.
- What safety factor should I use?
- 1.5 (150% of steam output) is a common industry practice default, though some applications use higher factors — check your boiler manufacturer's recommendation.
- Why convert from lbs/hr to GPM?
- Steam output is measured by mass flow (lbs/hr), but pumps are rated by volumetric flow (GPM) — the conversion uses water's density of 8.34 lbs per gallon.
Last updated 7/12/2026