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Booster Pump Sizing Calculator: Head, Flow & Horsepower
Estimate booster-pump pressure rise, head, and hydraulic horsepower from supply and target conditions.
Method record
What this calculator measures
Booster sizing starts with the duty point: required flow and additional head. Supply variation can create both low-pressure design conditions and high-pressure component risks.
Required head = (outlet PSI − inlet PSI) × 2.31 + elevation + friction Use it correctly
Calculation steps
- Set peak design flow.
- Use minimum credible inlet pressure.
- Check the selected curve, controls, tank, motor, NPSH, and maximum pressure.
Applicability
Use the model within its limits
Final design needs demand analysis, backflow and utility requirements, controls, redundancy, surge protection, and licensed review.
What this result represents
- System
- Pump
- Formula
- Required head = (outlet PSI − inlet PSI) × 2.31 + elevation + friction
- Review
- Verify safety-sensitive work with qualified guidance.
Worked Field Example
Worked Example: Commercial Building Booster Pump Sizing
Field Scenario: Sizing a water booster pump for a 3-story commercial facility where municipal street pressure drops to 30 PSI, but fixtures require 65 PSI at 40 GPM peak demand.
Given Input Parameters
Step-by-Step Mathematical Solution
- Elevation head in PSI = 28 ft / 2.307 ≈ 12.13 PSI.
- Total boost pressure: ΔP = (65.0 - 30.0) + 12.13 + 6.0 = 53.13 PSI.
- Convert boost to feet of head: 53.13 × 2.307 ≈ 122.6 feet.
- Hydraulic Horsepower: Whp = (53.13 × 40.0) / 1714 ≈ 1.24 HP.
- Brake Horsepower at 65% pump efficiency: BHP = 1.24 / 0.65 ≈ 1.91 BHP.
Requires 53.1 PSI boost (122.6 ft head) at 40 GPM; specify a 2.0 HP multi-stage centrifugal booster pump.
Professional Guidance: Select a Variable Frequency Drive (VFD) booster package to maintain constant pressure regardless of fluctuating municipal supply.
Engineering FAQs
Frequently Asked Questions
When is a water pressure booster pump required?
A booster pump is needed when municipal supply or well pressure drops below 40–50 PSI at ground level, or when multi-story elevation head loss (0.433 PSI per vertical foot) reduces pressure at upper fixtures below minimum code requirements (typically 20–30 PSI residual at the highest fixture).
Why is a backflow preventer and pressure reducing valve (PRV) often paired with booster pumps?
Plumbing codes require backflow preventers to protect the public water supply from cross-contamination. If city street pressure spikes at night, a booster pump with constant boost can overpressurize fixtures beyond the 80 PSI plumbing code limit; a PRV prevents overpressurization.
What is the advantage of a variable speed (VFD) booster pump over a fixed-speed system?
A VFD booster continuously modulates pump impeller speed to maintain a rock-solid discharge pressure (e.g. exactly 60 PSI) regardless of whether one faucet is open or ten showers are running, eliminating pressure fluctuations and saving substantial electricity.